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Tekenya, Ronald. "Graphene-modified pencil graphite mercury-film electrodes for the determination of trace metals by cathodic adsorptive stripping voltammetry." University of the Western Cape, 2018. http://hdl.handle.net/11394/6552.
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>Magister Scientiae - MSc<br>This project focuses on the simple, fast and highly sensitive adsorptive stripping voltammetry
detection of Nickel and Cobalt complexed with DMG and Nioxime respectively at a Reduced
Graphene Oxide modified pencil graphite electrode in water samples. This research as well
demonstrates a novel electrochemically reduced graphene oxide (ERGO)/mercury film (MF)
nanocomposite modified PGE, prepared through successive electrochemical reduction of graphene
oxide (GO) sheets and in-situ plated mercury film. The GO and graphene were characterized using
FT-IR, HR-SEM, HR-TEM, XRD and Raman spectroscopy. The FT-IR results supported by Xray
diffraction analysis confirmed the inclusion of oxygen moieties within the graphitic structure
during the chemical oxidation step. Microscopic and spectroscopic analysis was used to confirm
the stackings of graphene on the pencil electrode. The ERGO-PG-MFE, in combination with a
complexing agents of [dimethylglyoxime (DMG) and Nioxime] and square-wave cathodic
stripping voltammetry (SW-CSV), was evaluated towards the individual determination of Ni2+
and Co2+ respectively and simultaneous determination of both metals from the combination of
DMG and Nioxime mixture. A single-step electrode pre-concentration approach was employed for
the in-situ Hg-film electroplating, metal-chelate complex formation and its non-electrolytic
adsorption at – 0.7 V for the individual analysis of Ni2+ and Co2+. The current response due to
metal-ligand(s) complex reduction were studied as a function of experimental variables;
deposition/accumulation potential, deposition/accumulation time, rotation speed, frequency and
amplitude and carefully optimized for the individual determination of Ni2+and Co2+ and
simultaneous determination of Ni2+ and Co2+ at low concentration levels (μg L-1) in 0.1 M NH3-
NH4Cl buffer solution (pH 9.4) solution. The recorded limit of detection for the individual analysis
of Ni2+and Co2+ was found to be 0.120 μg L-1 and 0.220 μg L-1 respectively, at an accumulation
time of 120 s for both metals. The recorded limit of detection of the simultaneous analysis of Ni2+
and Co2+ was found to be 6.1 μg L-1 and 1.8 μg L-1 respectively. The ERGO-PG-MFE further
demonstrated a highly selective stripping response toward all trace metal analysis. The testing of
the applicability of graphene-based sensor and method in laboratory tap water samples was
evaluated. This electrode was found to be sensitive enough to detect metal ions in the tap water
samples at the 0.2 μg L-1 level for individual analysis and 0.001 μg L-1 for simultaneous, well
below WHO standards.
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Sanga, Nelia Abraham. "Determination of heavy metals at the electrochemically reduced graphene oxide mercury film electrode (ERGO-HgF-PGE) using adsorptive stripping voltammetry." University of Western Cape, 2020. http://hdl.handle.net/11394/7718.
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>Magister Scientiae - MSc<br>This work reports the use of a pencil graphite electrode (PGE) as inexpensive and sensitive
electrochemical sensing platform fabricated by using electrochemically reduced graphene oxide
(ERGO) in conjunction with an in-situ plated thin mercury film. For the first time the ERGOHgF-PGE sensor is proposed for simultaneous detection of cadmium (Cd2+), copper (Cu2+), lead
(Pb2+) and zinc (Zn2+) using N-Nitroso-N-phenylhydroxylamine (cupferron) as complexing agent
by square-wave adsorptive cathodic stripping voltammetry (SW-AdCSV). The technique is
based on the adsorption of cupferron- metal ion complexes onto the surface of the ERGO-HgFPGE at 0.1 V for 60 s carried out in 0.1 M acetate buffer solution (pH 4.6). The synthesized
graphene oxide (GO) and graphene nanosheets (GNs) were characterized using different
analytical techniques such as FT-IR which confirms the presence of oxygen moieties embedded
in the graphitic structure and further demonstrated by UV-Vis, validating the synthesis of GO<br>2023
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Le, Louie. "Nanocomposites and graphene oxide thin film coatings on the surface of fiber reinforced composites for enhanced flame retardancy." Thesis, Wichita State University, 2013. http://hdl.handle.net/10057/6425.
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Pant, Bharat Raj. "A Comparative Study on P-type Nickel Oxide and N-type Zinc Oxide for Gas Sensor Applications." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1525473245395728.
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Dorenkamp, Yvonne Jeannette. "Inelastic H-Atom scattering from ultra-thin films." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://hdl.handle.net/11858/00-1735-0000-002E-E49B-7.
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Ferrah, Djawhar. "Etude des propriétés physico-chimiques d'interfaces par photoémission." Thesis, Ecully, Ecole centrale de Lyon, 2013. http://www.theses.fr/2013ECDL0048/document.
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L'objectif de cette thèse est d'étudier les propriétés physico-chimiques des surfaces et des interfaces des couches minces par spectroscopie de photoémission (XPS), diffraction des photoélectrons (XPD), et la photoémission résolue en temps (PTR). Les expériences sont réalisées en utilisant une source standard des rayons X AlKa à l'INL ou les rayons X mous auprès du synchrotron Soleil. La première étude sur le système Pt/ Gd203/ Si(111) a montré que le transfert de charge entre le Pt et 0 à l'interface Pt/Gd203 implique un déplacement chimique de niveau Pt4f sans modification des caractéristiques de la composante métallique des spectres XPS. L'étude XPD montre que Pt se cristallise partiellement en deux domaines : [110] Pt(111) // [110] Gd203 (111) et [101] Pt(111) / / [110] Gd203 (111). De plus, une autre phase ordonnée d'oxyde de platine Pt02 à l'interface a été observée. A travers la caractérisation de la morphologie déterminée par la technique AFM et XPD, nous avons discuté l'adhésion aux interfaces métal/oxyde. La deuxième étude traite l'évolution d'interface d'un système modèle : métal non réactive/ semi-conducteur, dépendent fortement des conditions thermodynamiques. Nous avons étudié la couche mince d'Au déposée sur le substrat Si(001) par photoémission résolue en temps (TEMPO- synchrotron Soleil). L'étude XPS, montre avant le recuit la formation de l'oxyde native Si02 sur l'heterostructure à température ambiante. La désorption de cet oxyde se produit à faible température et induit une décroissance de l'intensité des photoélectrons durant le temps de recuit. La désorption de l'oxyde Si02 et la formation de l'alliage AuSi sont responsables de la gravure et la formation des puits de forme cubique à la surface de Si due à l'activité catalytique de l'Au. La troisième étude concerne la croissance du graphène à partir de cristal de SiC(0001)- face Si par décomposition thermique. Le niveau de coeur C1s résolu en trois composantes principales sont associées au carbone de 6H-SiC, de graphène, et l'interface graphène/ 6H-SiC (0001). L'intensité de chaque composante est rapportée en fonction de l'angle polaire (azimutale) pour différents angles azimutales (polaire). Les mesures XPD fournissent des informations cristallographiques qui indiquent clairement que les feuillets de graphène sont organisés en structure graphite sur le substrat 6H-SiC (0001). Cette organisation résulte de l’effondrement de la maille de substrat. Enfin, le découplage à l'interface graphène/ 6H-SiC (0001) par l'oxygène a été étudié par XPS. La dernière étude concerne la croissance du film mince d'InP par MBE sur le substrat SrTi03 (001). L'intégration des semi-conducteurs III-V sur le Si, en utilisant la couche tampon d'oxyde SrTi03 est l'objet des intenses recherches, en raison des applications prometteuses dans le domaine de nano-optoélectronique. Les niveaux de coeur O1s, Sr3d, Ti2p, In3d, P2p ont été analysés et rapportés en fonction de l'angle azimutale à différents angles polaires. La comparaison des courbes XPD azimutales de Sr3d et In3d montre que les ilots InP sont orientées (001) avec la relation d'épitaxie; [110]InP(001 )/ / [100]! SrTi03 (001). La caractérisation morphologique par AFM montre des ilots InP facettés régulièrement dispersée à la surface<br>The main objective of this thesis is to study the chemical and physical properties at the surface or at the interface between thin layers by photoemission spectroscopy (XPS), photoelectron diffraction (XPD), and time resolved photoemission (PTR) . The experiments were conducted using an Alka source at INL or soft -X ray synchrotron radiation at Soleil, the French national Synchrotron facility. The first photoemission study has been performed on platinum deposited on thin Gd2(h layers grown by Molecular Bearn Epitaxy (MBE) on Si (111) substrate. The charge transfer between Pt and 0 at the interface causes a chemical shift to higher binding energies without changing the characteristic shape of the metal XPS peak. The XPD study shows that Pt is partially crystallized into two (111)-oriented do mains on Gd20 3 (111) with the in-plane epitaxial relationships [11 0] Pt (111) / / [11 0] Gd203 (111) and [101] Pt(111)/ / [11 0] Gd20 3 (111). In addition to bi-domains formation of platinum Pt (111) on Gd20 3 (111), a new ordered phase of platinum oxide Pt02 at the Pt/ Gd203 interface have been observed. The study of the background of the polar curves depending of the morphology has shown, that the film of Pt does not wet on the oxide, due to the low energy of interaction at the interface compared to the Pt thin layer. The second study has been interested to the photoemission time-resolved study of non-reactive metal / semiconductor model system. We have studied the thin layer gold (Au) growth on silicon (Si) substrate before and during annealing in TEMPO beam line (synchrotron Soleil).The XPS study, shows before annealing the formation of silicon native oxide on heterostructure at ambient temperature. The desorption of silicon oxide during annealing at low temperature induce photoemission intensity decreases with time. The desorption of oxide and alloy formation (AuSi) induce distribution of pits with cubic form at silicon surface due to gold etching activity. The third photoemission study has concerned thin films of a few layers of graphene obtained by solid-state graphitization from 6H-SiC (0001) substrates have been studied by X-ray photoelectron spectroscopy (XPS) and X-ray photoelectron diffraction (XPD). The Cls core-level has been resolved into components, which have been associated with carbon from bulk SiC, carbon from graphene and carbon at the interface graphene/ 6H-SiC (0001). Then, the intensity of each of these components has been recorded as a function of polar (azimuth) angle for several azimuth (polar) angles. These XPD measurements provide crystallographic information which clearly indicates that the graphene sheets are organized in graphite-like structure on 6H-SiC(0001), an organization that results of the shrinking of the 6H-SiC (0001) lattice after Si depletion. Finally the decoupling of graphene from 6H-SiC (0001) substrate by oxygen intercalation has been studied from the XPS point of view. Finally, photoemission study has concerned thin film of InP (phosphor indium ) islands grown by Molecular Bearn Epitaxy (MBE) on SrTi03 (001) bulk substrate have been investigated by X-ray photoelectron spectroscopy and diffraction (XPS/ XPD).Integration of III-V semi-conductor on silicon wafer, via SrTi03 buffer is currently the subject of intense research because of its potentially interesting applications in future nano-optoelectronics. The Ols, Sr3d, Ti2p, In3d, and P 2p core level area have been studied as function of azimuth angle for different polar angles. Comparison of the XPD azimuth curves of Sr3d and In3d shows that islands InP are oriented (001) with an in-plane epitaxial relationship [110] InP(001 ) // [100] SrTi03 (001). AFM images shows that InP islands are regularly dispersed on the surface. Their shape is a regularly facetted half-sphere
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Ly, Kally Chein Sheng 1992. "Fabricação e caracterização de filme fino regenerável hidrofóbico." [s.n.], 2017. http://repositorio.unicamp.br/jspui/handle/REPOSIP/330349.
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Orientador: Antonio Riul Júnior<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin<br>Made available in DSpace on 2018-09-02T14:50:41Z (GMT). No. of bitstreams: 1
Ly_KallyCheinSheng_M.pdf: 2442128 bytes, checksum: 86716c6c19fa3a9db425b32c36463141 (MD5)
Previous issue date: 2017<br>Resumo: Materiais biomiméticos são inspirados em estruturas biológicas para a obtenção de propriedades e funcionalidades específicas. Dentre os materiais biomiméticos, os que são capazes de se regenerar (self-healing) despertaram grande interesse pelo potencial de aplicação em diversas áreas. Para ilustrar, alguns materiais autorregeneráveis poliméricos apresentam regeneração múltipla, necessitando apenas de água para que a regeneração ocorra em alguns minutos, aumentando consideravelmente a proteção mecânica da superfície contra desgastes, danos mecânicos entre outros. Entretanto, múltiplas imersões em água ou em meios aquosos pode degradar o material e neste contexto este projeto visa incorporar a hidrofobicidade a um sistema regenerável. Desta forma, o material regenerável hidrofóbico, durante sua regeneração imersa em água, poderá diminuir a interação da superfície não danificada com a água, reduzindo corrosões e degradações devido a meios aquosos. Estudamos a nanoestruturação de materiais através da técnica de automontagem por adsorção física (LbL, do inglês Layer-by-Layer) utilizando os polieletrólitos poli(etileno imina) (PEI) e poli(ácido acrílico) (PAA), a fim de produzir revestimentos capazes de se regenerar a danos mecânicos micrométricos. Adicionalmente, foram incorporados a estes dois materiais nanofolhas de óxido de grafeno reduzido (rGO) funcionalizados com poli(cloridrato de alilamina) (GPAH) e poli(estireno-sulfonato de sódio) (GPSS), com o intuito de verificarmos um aumento de resistência a abrasão do material e alterações nas propriedades elétricas na nanoestrutura formada para aumentar o potencial de aplicação em eletrônica flexível. A arquitetura molecular (GPAH-PEI/GPSS-PAA)60 foi caracterizada com espectroscopia Raman, medidas de ângulo de contato, microscopia de força atômica, medidas elétricas e nanoindentação. Foi observada boa regeneração do material após 15 minutos de imersão em água a temperatura ambiente em um dano mecânico da ordem de 10 micrômetros. Também observamos boa hidrofobicidade do filme LbL (GPAH-PEI/GPSS-PAA)60 ( teta = 136º), e medidas de microscopia de força atômica e perfilometria indicaram, respectivamente, rugosidade superficial de 55 nm em uma área de (2 ?m x 2 ?m) e espessura de filme de 30 ?m. A análise Raman apontou para uma forte interação das nanofolhas de rGO com os polímeros, corroborando o tem caráter elétrico isolante do filme (GPAH-PEI/GPSS-PAA)60, que apresentou função trabalho ~ 5,2 eV e condutividade elétrica da ordem de 10-7 S/cm, que acreditamos resultar das fortes interações das nanofolhas com os polímeros. Por fim, medidas de nanoindentação indicaram que a incorporação de nanofolhas de GPSS e GPAH aumentou em 10 vezes a dureza do nanocompósito formado, sem comprometer a regeneração<br>Abstract: Biomimetic materials are inspired in biological structures to obtain specific properties and functionalities and among them, those capable of self-healing brought great interest due to high potential of application in different areas. To illustrate, some polymeric self-healing materials present multiple regeneration in the presence of water, with the regeneration occurring within a few minutes, increasing considerably the mechanical protection of a surface against wear and mechanical damage among others. Nevertheless, multiple immersions in water or in aqueous media can degrade the material and in this context this project aims the incorporation of hydrophobicity to a self-healing system. In this way, the self-healing, hydrophobic material during its immersion in water may decrease the interaction of the damaged surface with water, reducing corrosion and degradation due to aqueous media. We study the nanostructuration f materials through the layer-by-layer (LbL) technique using poly(ethylene imine) (PEI) and poly(acrylic acid) (PAA) in order to produce self-healing coatings from micrometric mechanical damages. In addition, we also incorporate to these materials reduced graphene oxide (rGO) functionalized with poly(allylamine hydrochloride) (GPAH) and poly(styrene-sodium sulfonate) (GPSS), with the purpose of verifying an increase in the mechanical abrasion resistance of the material and changes in the electrical properties of the nanostructures formed to increase the potential application in flexible electronics. The molecular architecture (GPAH-PEI/GPSS-PAA)60 was characterized by Raman spectroscopy, contact angle measurements, atomic force microscopy, electrical measurements and nanoindentation. It was observed good self-healing capacity after 15 min f immersion in water at room temperature in a mechanical scratch of the order of 10 micrometers. It was also observed good hydrophobicity in the (GPAH-PEI/GPSS-PAA)60 LbL film ( teta = 136º) and atomic force microscopy and perfilometer indicate, respectively, surface roughness of 55 nm in a (2 ?m x 2 ?m) area and film thickness of 30 ?m. Raman analysis pointed out to a strong physical interaction between the rGO nanoplatelets with the polymeric materials, corroborating the strong insulating nature of (GPAH-PEI/GPSS-PAA)60 film that displayed a work function of 5.2 eV and electrical conductivity of 10-7 S/cm, which we believe results from the strong interactions of the nanosheets with the polymers. Finally, nanoindentation measurements indicated that the incorporation of GPAH and GPSS nanoplatelets increased hardness by 10 times, without compromising the regeneration<br>Mestrado<br>Física<br>Mestra em Física<br>1543078/2015<br>CAPES
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Lacovig, Paolo. "Electronic structure, morphology and chemical reactivity of nanoclusters and low-dimensional systems: fast photoemission spectroscopy studies." Doctoral thesis, Università degli studi di Trieste, 2010. http://hdl.handle.net/10077/3685.
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2008/2009<br>L'obiettivo di questa tesi è l'applicazione della spettroscopia di fotoemissione allo
studio di nanoparticelle supportate e di sistemi a bassa dimensionalità.
Ad una primo periodo dedicato allo sviluppo del rivelatore e del software
per un nuovo analizzatore d'energia per elettroni installato presso la linea
di luce SuperESCA ad Elettra, è seguita una fase durante la quale ho eseguito una serie di esperimenti mirati ad esplorare le potenzialità del nuovo apparato sperimentale.
Il primo risultato ottenuto riguarda la comprensione della relazione che
intercorre tra le variazioni della reattività chimica del sistema Pd/Ru(0001) e il numero degli strati di Pd cresciuti in modo pseudomorfico sul substrato di rutenio.
La risoluzione temporale raggiunta con la nuova strumentazione ci ha permesso di studiare processi dinamici su una scala temporale fino ad ora inaccessibile per la spettroscopia di fotoemissione dai livelli di core: in particolare abbiamo studiato la crescita del grafene ad alta temperatura sulla superficie (111) dell'iridio e la reattività chimica di nanocluster di Pt supportati su MgO. Nel primo caso abbiamo messo in evidenza come la formazione del grafene proceda attraverso la nucleazione di nano-isole di carbonio che assumono una peculiare forma di cupola. Nel secondo caso siamo riusciti a seguire sia la dinamica del processo di adsorbimento di CO, sia la reazione CO + 1/2 O2 -> CO2 sulle nanoparticelle di Pt depositate su un film ultra-sottile di ossido di magnesio.
Infine, abbiamo caratterizzato la morfologia di nanoparticelle di Pd, Pt, Rh e Au cresciute su diversi substrati a base di carbonio, in particolare grafite, nanotubi a parete singola e grafene. Tra i vari risultati abbiamo compreso come l'interazione metallo-substrato dipenda dalla dimensione delle nano-particelle e abbiamo evidenziato il ruolo centrale dei difetti del substrato nei processi di nucleazione e intercalazione.<br>The objective of this thesis is the application of photoelectron spectroscopy for the investigation of supported nanoclusters and low-dimensional systems.
After a first stage devoted to the development of the detector and the software for the electron energy analyser installed on the SuperESCA beamline at Elettra, during the PhD project I've performed a series of experiments aimed to explore the capabilities of the new experimental apparatus.
One of the first results concerns the understanding of the relation between the modifications in the chemical reactivity of the Pd/Ru(0001) system and the thickness of the pseudomorphically grown Pd overlayer.
The temporal resolution achieved with the new experimental set-up allowed us to study dynamical processes on a new time scale, in particular the graphene growth process at high temperature on the Ir(111) surface and the chemical reactivity of Pt nanoclusters supported on MgO. In the former case, we discovered that graphene formation proceeds via preliminary nucleation of dome-shaped C nano-islands. In the second case, we succeded in following both the dynamics of CO adsorption process and the CO + 1/2 O2 -> CO2 reaction on Pt nanoclusters grown on a ultra-thin film of magnesium oxide.
Finally, the morphology of Pd, Pt, Rh and Au nanoclusers grown on different carbon-based substrates (namely graphite, single-walled carbon nanotubes and graphene) has been characterized. Among the results we report the understanding of the dependence of the metal-substrate interaction on the cluster size and the role of defects in the nucleation and intercalation processes.<br>XXII Ciclo<br>1972
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Guan, Jingcheng. "Modelling zinc oxide thin-film growth." Thesis, Loughborough University, 2018. https://dspace.lboro.ac.uk/2134/36311.
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Photovoltaics have a significant role in the solution of energy supply and energy security. Research on photovoltaic devices and their production processes has been carried out for decades. The transparent conducting oxide layer, in the photovoltaic solar cell, composed of aluminium doped zinc oxide, is produced through deposition techniques. By modelling these depositions using classical molecular dynamics, a better understanding on the short term kinetics occurring on the growing surface has been achieved. Compared to the molecular dynamics, the employment of the adaptive kinetic Monte Carlo method enabled such surface growth dynamics simulation to reach much longer time scale. Parallelised transition searching was carried out in an on-the-fly manner without lattice approximation or predefined events table. The simulation techniques allowed deposition conditions to be easily changed, such as deposition energy, deposition rate, substrate temperature, plasma pressure, etc. Therefore, in this project three main deposition techniques were modelled including evaporation (thermal and assisted electron beam), reactive magnetron sputtering and pulsed laser depositions. ZnO as a covalent compound with many uses in semiconductors was investigated in its most energy favourable wurtzite configuration. The O-terminated surface was used as the substrate for the growth simulation. Evaporation deposition at room temperature (300 K) with a stoichiometric distribution of deposition species produced incomplete new layers. Holes were observed existing for long times in each layer. Also, stacking faults were formed during the low-energy (1 eV) growth through evaporation. The reactive sputtering depositions were more capable of getting rid of these holes structures and diminished these stacking faults through high energy bombardments but could also break these desirable crystalline structure during the growth. However, single deposition results with high energies showed that the ZnO lattice presented good capacity of self-healing after energetic impacts. Additionally, such self-healing effects were seen for substrate surface during thin film growth by the sputtering depositions. These facts shed some light on that the sputtering technique is the method of choice for ZnO thin film depositions during industrial production. Simulation results of pulsed laser deposition with separated Zn and O species showed the thin films were grown in porous structures as the O-terminated surface could be severely damaged by Zn atoms during the very short pulse window (10 microseconds). An important growth mechanism with ZnO dimer deposited on the O-terminated polar surface was the coupling of these single ZnO dimers, forming highly mobile strings along the surface and thus quenching its dipole moments, whilst the isolated single ZnO dimers were hardly of this mobility. Such strings were the building blocks for the fabrication occurring on the surface resulting in new layers. Last but not least, a reactive force field for modelling Al doped ZnO was fitted. DFT calculations showed that the Al atoms on the surface were likely to replace Zn atoms in their lattice sites for more energy favourable structures. Al on the ZnO surfaces, structures with Al in the bulk as well as configurations with Al interstitials were used to train the force field to reproduce favourable surface binding sites, cohesive energies and lattice dimensions. The combination scheme of MD and the AKMC allowed simulation work to reach over experimentally realistic time scale. Therefore, crucial mechanisms occurring during the growth could be precisely understood and investigated on an atomistic level. It has been shown from the simulation results that certain types of deposition play significant roles in the quality of resultant thin films and surface morphology, thus providing insight to the optimal deposition conditions for growing complete crystalline ZnO layers.
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Li, Sonny X. "Nitrogen doped zinc oxide thin film." Berkeley, Calif. : Oak Ridge, Tenn. : Lawrence Berkeley National Laboratory ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2003. http://www.osti.gov/servlets/purl/821916-VLVAK9/native/.
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Thesis (M.S.); Submitted to the University of California, Berkeley, 210 Hearst Mining Memorial Bldg., Berkeley, CA 94720 (US); 15 Dec 2003.<br>Published through the Information Bridge: DOE Scientific and Technical Information. "LBNL--54116" Li, Sonny X. USDOE Director. Office of Science. Basic Energy Sciences (US) 12/15/2003. Report is also available in paper and microfiche from NTIS.
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Özkan, Zayim E., and N. Karamahmutoglu. "Carbon Nanotubes Doped Vanadium Oxide Thin Film." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35004.
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Vanadium oxide films were prepared by chemical coating techniques on glass and ITO coated glass
substrates. Vanadium oxide films were doped with carbon nanotubes and examined their optical band gap
and structures. The effects of carbon nanotubes on visible light absorbance and band gap energies were observed.
Electrochemical, structural and optical studies on vanadium oxide coatings were reported in the
liquid electrolyte. Optical constant such as refractive index, extinction coefficient, and band gap calculation
was done by NKD analyzer. Effect of CNT into vanadium oxide films structural properties were examined
by atomic force microscopy (AFM)
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35004
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Meng, Keng-Yuan. "Magnetic Skyrmions in Oxide Thin Film Heterostructures." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1562856036665345.
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Zhang, Jiawei. "Oxide-semiconductor-based thin-film electronic devices." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/oxidesemiconductorbased-thinfilm-electronic-devices(c8cde776-b68b-47b5-ab63-382a86dbb94b).html.
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Oxide semiconductors have been envisaged to find applications in ubiquitous flexible electronics in daily life such as wearable electronic gadgets to offer novel user experiences. However, one of the bottlenecks to realise these applications is a lack of oxide-semiconductor components capable of wireless communications. As Bluetooth and Wi-Fi are the two dominant communication interfaces, fast enough front-end rectifiers must be developed to operate at their gigahertz (GHz) transmission frequencies. Furthermore, despite of significant developments of n-type oxide semiconductors in the last decade, widespread flexible electronics also requires high-performance p-type oxide semiconductors for use in complementary logic circuits. The objectives of this dissertation are to develop high quality Schottky barriers, achieve GHz speed Schottky diodes on rigid and flexible substrates, evaluate the noise properties of the Schottky diodes, develop p-type oxide semiconductor using sputtering technology, elucidate the hole transport mechanism in p type transistors, and demonstrate their potential applications such as radio receivers, complementary inverters and ring oscillators. First, indium gallium zinc oxide (IGZO) Schottky diodes were fabricated by using radio frequency magnetron sputtering. The oxygen content at the metal-IGZO interface was found to have a profound effect on the electrical performance. By introducing 3% O2 during the deposition of Pt or IGZO, the diodes exhibited excellent electrical properties without requiring any annealing treatment, thus allowing for the realisation of flexible IGZO Schottky diodes. The high-frequency properties of Pt-IGZO Schottky diodes on glass substrates were optimised by testing a range of IGZO thicknesses and diode active areas. The achieved highest cut-off frequency was beyond 20 GHz, which is to the best of our knowledge the fastest oxide-semiconductor device to date. On flexible substrates, the diodes also showed cut-off frequencies up to 6.3 GHz, well beyond the critical benchmark speed of 2.45 GHz for typical wireless communications. In order to assess the feasibility of using IGZO Schottky diodes in practical applications, measurements were taken to discern their low-frequency noise properties. In the as-deposited diodes, logarithmic dependence of the noise spectral density on the applied bias was observed, revealing that the dominant noise was generated in the space-charge region at low biases and in the series-resistance region at high biases, respectively. After annealing the diodes, very different noise mechanism was observed and the interface-trap-induced noise dominated the noise spectra. As one of the most promising p-type oxide semiconductors, SnO was also studied at low temperatures in this thesis. The experiment revealed that hole-transport mechanism was governed by either band conduction or variable range hopping in different temperature ranges. Finally, the potential for fully oxide-based electronics was demonstrated by an amplitude-modulation radio receiver comprising of an IGZO Schottky diode as the demodulator and a complementary ring oscillator based on IGZO and SnO transistors. In reference to IEEE copyrighted material which is used with permission in this thesis, the IEEE does not endorse any of the University of Manchester's products or services. Internal or personal use of this material is permitted. If interested in reprinting/republishing IEEE copyrighted material for advertising or promotional purposes or for creating new collective works for resale or redistribution, please go to http://www.ieee.org/publications_standards/publications/rights/rights_link.html to learn how to obtain a License from RightsLink.
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Čuboň, Tomáš. "Studium optických vlastností tenkých vrstev organických fotovoltaických článků." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2017. http://www.nusl.cz/ntk/nusl-316198.
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This master´s thesis is focused on measurement of optical properties of thin layer of materials used in organic solar cells (OSC). The usage of graphene oxides and its reduced forms as parts of hole transport layer (HLT) in OSC were studied. At the beginning of the thesis, there is described basic theory necessary to understand the optical properties of thin layers. The thin layer deposition and reduction of GO are discussed too. The experimental part is aimed to the optical characterization of prepared thin films. The results from optical microscopy, UV-VIS spectroscopy, FT-IR spectroscopy and spectroscopic ellipsometry were obtained. At the end of the thesis, the results are concluded and compared with already published literature.
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Han, Sanggil. "Cu2O thin films for p-type metal oxide thin film transistors." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/285099.
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The rapid progress of n-type metal oxide thin film transistors (TFTs) has motivated research on p-type metal oxide TFTs in order to realise metal oxide-based CMOS circuits which enable low power consumption large-area electronics. Cuprous oxide (Cu2O) has previously been proposed as a suitable active layer for p-type metal oxide TFTs. The two most significant challenges for achieving good quality Cu2O TFTs are to overcome the low field-effect mobility and an unacceptably high off-state current that are a feature of devices that have been reported to date. This dissertation focuses on improving the carrier mobility, and identifying the main origins of the low field-effect mobility and high off-state current in Cu2O TFTs. This work has three major findings. The first major outcome is a demonstration that vacuum annealing can be used to improve the carrier mobility in Cu2O without phase conversion, such as oxidation (CuO) or oxide reduction (Cu). In order to allow an in-depth discussion on the main origins of the very low carrier mobility in as-deposited films and the mobility enhancement by annealing, a quantitative analysis of the relative dominance of the main conduction mechanisms (i.e. trap-limited and grain-boundary-limited conduction) is performed. This shows that the low carrier mobility of as-deposited Cu2O is due to significant grain-boundary-limited conduction. In contrast, after annealing, grain-boundary-limited conduction becomes insignificant due to a considerable reduction in the energy barrier height at grain boundaries, and therefore trap-limited conduction dominates. A further mobility improvement by an increase in annealing temperature is explained by a reduction in the effect of trap-limited conduction resulting from a decrease in tail state density. The second major outcome of this work is the observation that grain orientation ([111] or [100] direction) of sputter-deposited Cu2O can be varied by control of the incident ion-to-Cu flux ratio. Using this technique, a systematic investigation on the effect of grain orientation on carrier mobility in Cu2O thin films is presented, which shows that the [100] Cu2O grain orientation is more favourable for realising a high carrier mobility. In the third and final outcome of this thesis, the temperature dependence of the drain current as a function of gate voltage along with the C-V characteristics reveals that minority carriers (electrons) cause the high off-state current in Cu2O TFTs. In addition, it is observed that an abrupt lowering of the activation energy and pinning of the Fermi energy occur in the off-state, which is attributed to subgap states at 0.38 eV below the conduction band minimum. These findings provide readers with the understanding of the main origins of the low carrier mobility and high off-state current in Cu2O TFTs, and the future research direction for resolving these problems.
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Rossi, Leonardo. "Flexible oxide thin film transistors: fabrication and photoresponse." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14542/.
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Gli ossidi amorfi semiconduttori (AOS) sono nuovi candidati per l’elettronica flessibile e su grandi aree: grazie ai loro legami prevalentemente ionici hanno una mobilità relativamente alta (µ > 10cm^2/Vs) anche nella fase amorfa. Transistor a film sottile (TFT) basati sugli AOS saranno quindi più performanti di tecnologie a base di a-Si e più economici di quelle a base di silicio
policristallino. Essendo amorfi, possono essere depositati a basse temperature e su substrati polimerici, caratteristica chiave per l’elettronica flessibile e su grandi aree. Per questa tesi, diversi TFT sono stati fabbricati e caratterizzati nei laboratori del CENIMAT all’Università Nova di Lisbona sotto la supervisione del Prof. P. Barquinha. Questi dispositivi sono composti di contatti in molibdeno, un canale semiconduttivo di ossido di zinco, gallio e indio (IGZO) e un dielettrico composto da 7 strati alternati di SiO2 e SiO2+Ta2O5. Tutti i dispositivi sono stati depositati mediante sputtering su sostrati flessibili (fogli di PEN). Le misure tensione-corrente mostrano che i dispositivi mantengono alte mobilità (decine di 10cm^2/Vs) anche quando fabbricati a temperature inferiori a 200°C. Si è analizzato il funzionamento dei dispositivi come fototransistor rilevando la risposta alla luce ultravioletta e in particolare la loro responsività e spostamento della tensione di soglia in funzione della lunghezza d’onda incidente. Questi risultati consentono di formulare ipotesi sul comportamento dei dispositivi alla scala microscopica. In particolare, indicano che i) la mobilità del canale non è influenzata dall’illuminazione, ii) sia l'IGZO sia il Ta2O5 contribuiscono al processo di fotoconduttività e iii) il processo di fotogenerazione non è adiabatico. La tesi contiene inoltre una descrizione del processo di ricombinazione e presenta un’applicazione pratica di tali dispositivi in un circuito per RFID. Infine, esplora la possibilità di migliorarne la flessibilità e le prestazioni.
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Barnes, Jean-Paul L. P. Barnes. "TEM studies of thin film oxide/metal nanocomposites." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398136.
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Lloyd, Adam L. "Modelling silver thin film growth on zinc oxide." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/24860.
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Ag thin film growth on ZnO substrates has been investigated theoretically using multi-timescale simulation methods. The models are based on an atomistic approach where the interactions between atoms are treated classically using a mixture of fixed and variable charge potential energy functions. After some preliminary tests it was found that existing fixed charge potential functions were unreliable for surface growth simulations. This resulted in the development of a ReaxFF variable charge potential fitted to Ag/ZnO surface interactions. Ab initio models of simple crystal structures and surface configurations were used for potential fitting and testing. The dynamic interaction of the Ag atoms with the ZnO surface was first investigated using single point depositions, via molecular dynamics, whereby the Ag impacted various points on an irreducible symmetry zone of the ZnO surface at a range of energies. This enabled the determination of the relative numbers of atoms that could penetrate, reflect or bond to the surface as a function of incident energy. The results showed that at an energy of up to 10 eV, most atoms deposited adsorbed on top of the surface layer. The second part of the dynamic interaction involved a multi-timescale technique whereby molecular dynamics (MD) was used in the initial stages followed by an adaptive kinetic Monte Carlo (AKMC) approach to model the diffusion over the surface between impacts. An impact energy of 3 eV was chosen for this investigation. Ag was grown on various ZnO surfaces including perfect polar, O-deficient and surfaces with step edges. Initial growth suggests that Ag prefers to be spread out across a perfect surface until large clusters are forced to form. After further first layer growth, subsequent Ag atoms begin to deposit on the existing Ag clusters and are unlikely to join the first layer. Ag island formation (as mentioned within the literature) can then occur via this growth mechanism. O-deficient regions of ZnO surfaces result in unfavourable Ag adsorption sites and cause cluster formation to occur away from O-vacancies. In contrast, ZnO step edges attract deposited Ag atoms and result in the migration of surface Ag atoms to under-coordinated O atoms in the step edge. Various improvements have been made to the existing methodology in which transitions are determined. A new method for determining defects within a system, by considering the coordination number of atoms, is shown to increase the number of transitions found during single ended search methods such as the relaxation and translation (RAT) algorithm. A super-basin approach based on the mean rate method is also introduced as a method of accelerating a simulation when small energy barriers dominate. This method effectively combines states connected by small energy barriers into a single large basin and calculates the mean time to escape such basin. To accelerate growth simulations further and allow larger systems to be considered, a lattice based adaptive kinetic Monte Carlo (LatAKMC) method is developed. As off-lattice AKMC and MD results suggest Ag resides in highly symmetric adsorption sites and that low energy deposition events lead to no penetrating Ag atoms or surface deformation, the on-lattice based approach is used to grow Ag on larger perfect polar ZnO surfaces. Results from the LatAKMC approach agree with off-lattice AKMC findings and predict Ag island formation. Critical island sizes of Ag on ZnO are also approximated using a mean rate approach. Single Ag atoms are placed above an existing Ag cluster and all transition states are treated as belonging to a single large super-basin . Results indicate that small Ag clusters on the perfect ZnO surface grow in the surface plane until a critical island size of around 500 atoms is reached. Once a critical island size is reached, multiple Ag ad-atoms will deposit on the island before existing Ag atoms join the cluster layer and hence islands will grow upwards. A marked difference is seen for second layer critical island sizes; second layer Ag islands are predicted to be two orders of magnitude smaller (< 7 atoms). This analysis suggests that Ag on ZnO (0001) may exhibit Stranski-Krastanov (layer plus island) growth.
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Young, Sheng-Yu. "DLC thin film assisted zinc oxide nanowires growth." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8613.
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Thesis (M.S.) -- University of Maryland, College Park, 2008.<br>Thesis research directed by: Dept. of Materials Science and Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Gavanier, Beatrice. "Stability of thin film insertion electrodes." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324003.
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Beckel, Daniel. "Thin film cathodes for micro solid oxide fuel cells." kostenfrei, 2007. http://e-collection.ethbib.ethz.ch/view/eth:29741.
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Wang, Chao-Hsiung. "The growth of thin film epitaxial oxide-metal heterostructures." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368667.
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Brown, J. R. "Tin oxide thin film gas sensors deposited by MOCVD." Thesis, Keele University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434038.
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Lee, S. "Physics and modeling of oxide semiconductor thin film transistors." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1400467/.
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In this thesis, we present an intensive investigation on the analytical models to describe the field-effect mobility, the current-voltage (I-V) characteristics, and the instability mechanisms in oxide TFTs, e.g. amorphous In-Ga-Zn-O TFTs. Here, we considered the unique material properties and underlying physics of it, such as the localized tail states, the potential barriers, and the oxygen vacancies. The derived mobility model and the I-V relation for oxide TFTs have been proposed for the first time, yielding a physically-based transistor model for the circuit design and simulation. Also, we developed an analytical method to extract the localized tail state profile to be used as a basis to derive those mobility and I-V models. Here, the relationship between the Fermi-level and gate voltage is derived analytically for the gate voltage-dependent expressions of each model. These models were simulated and compared with the experiments, providing a good agreement with each other. Regarding the instability study, we developed a quantitative analysis on the photoconductive gain due to the oxygen vacancy ionized under illumination, and proposed a gate-pulse spectroscopy to get the ionized oxygen vacancy profile in energy. These studies suggest a visible light sensor application to be embedded into a display panel, e.g. an interactive display, intentionally using the oxygen vacancy-rich layer, e.g. the In-Zn-O, incorporated into a bi-layer channel photo-TFT structure. Consequently, a complete analysis on device physics and modelling of the oxide TFTs is presented in this thesis, providing analytical and quantitative insights into the physics of the oxide TFTs, and their potential for future interactive and transparent electronic systems.
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Barquinha, Pedro. "Transparent oxide thin-film transistors: production, characterization and integration." Doctoral thesis, Faculdade de Ciências e Tecnologia, 2010. http://hdl.handle.net/10362/5380.
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Flack, Natasha. "Thin film components for solid oxide fuel Cells (SOFCs)." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/2007271/.
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Thin film components for solid oxide fuel cells (SOFCs) have been investigated in this thesis. This work focuses on electrolyte materials such as samarium doped ceria (SDC) and cathode materials including neodymium barium cobalt oxide (NBCO) and barium calcium yttrium iron oxide. Single layer growth of NBCO or SDC is achieved on single crystal strontium titanate (001) before these materials were grown via pulsed laser deposition as a bi-layer and multilayers. Ordered NBCO required deposition at 850°C, whereas it was found that the SDC grew with a lower surface roughness at lower temperatures of around 650°C. The motivation was to investigate how the conductivity is affected by the interfaces between these layers, as motivated by previous studies of yttrium stabilised zirconia (YSZ) with strontium titanate (STO). NBCO was found to be unstable at the temperatures required for AC impedance measurements. From the transmission electron microscopy (TEM) and Energy Dispersive X-ray (EDX) data there is likely migration of Nd into the SDC layers. The interfaces are also less sharp for the multilayer films deposited at the higher temperature for the SDC growth. However, in all cases the SDC growth appears more favourable in the TEM when compared to the NBCO, with some regions even showing Co-metal and fluorite structures potentially attributed to Co-Ox where we would expect to see the perovskite block. Thin films of barium calcium yttrium iron oxide were grown on single crystal strontium titanate (001). The material is a candidate cathode for solid oxide fuel cells (SOFCs) and in the intermediate temperature (IT) region at 600°C the in-plane AC conductivity of the thin film is found to be 30.0Scm-1, significantly enhanced over 3.5Scm-1 found for the polycrystalline form. This is assigned to reduction of the grain boundary density and alignment of the planes predicted to have the highest electronic and ionic conductivities. The symmetry of the film appears to be tetragonal within the resolution of the measurements employed, as opposed to the orthorhombic symmetry of the bulk phase, which may be attributed to the in-plane structural match between the cubic STO substrate and the grown layer. Three potential geometries investigating both single and double-sided growth for measuring the area specific resistance of thin films are discussed and an experimental prototype constructed and tested.
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Adam, Suhare A. "Thin Film Complex Oxide Proton Conductors: Synthesis and Applications." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493335.
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The performance of ultra-thin film solid oxide fuel cells (μ-SOFC) is highly dependent on the structural, microstructural and transport properties of the electrolyte. The focus of this thesis is on understanding the effect of synthesis and processing parameters of BaY0.2Zr0.8O3 (BYZ), a complex oxide proton-conducting electrolyte, on thin-film solid oxide fuel cell (SOFC) performance.
The properties of BYZ thin films are highly dependent on film growth techniques and parameters. The relationship between electrolyte thickness and fuel cell performance is investigated in the ultra-thin film thickness range of ~ 70 nm to ~ 200 nm for BYZ films grown by RF sputtering. The microstructure, crystal structure, and electrical behavior of BYZ films were examined as a function of thickness to attain high power density in SOFCs. The optimal thickness that allows for a balance between the leakage current and Ohmic resistance for these devices was determined to be t0 ~150 nm. XRD examination showed a thickness dependent stress behavior in BYZ thin films, with the most compressive state occurring for films of thickness t0. A Volmer-Weber thin film growth mode is proposed for the observed thickness dependent evolution in film properties. The findings of this examination can allow for an increase in the limits of SOFC power density in the ultra-thin regime for proton conducting electrolytes.
The presence of a large number of grain boundaries in BYZ films processed at intermediate temperatures leads to diminished conductivity. To mitigate this reduced conductivity while maintaining reasonable processing temperatures, it is essential to increase the effective surface area or TPB of the device. A study of the insertion of ion-selective interfacial layers between the electrode-electrolyte interfaces in μ-SOFCs performance is presented. A nearly two-fold increase in power density of μ-SOFCs in the intermediate temperature range is demonstrated by the addition of ultra-thin palladium interlayers. In addition to enhancing performance, this approach may yield important insight into the proton conduction behavior of BYZ and other proton conducting materials.
Finally, to address some of the shortcomings in the current synthesis techniques for BYZ, a novel intermediate temperature thin film synthesis route is demonstrated. This new technique (SP-GNP) is a combination of a thin film deposition technique, Spray Pyrolysis (SP), with a low temperature oxide powder synthesis technique, Glycine Nitrate Process (GNP). A proposed working mechanism and a discussion of the principal parameters that dictate film properties is presented. By using this technique, single-phase perovskite BYZ films were successfully grown at a temperature of 200 °C followed by annealing at 750 °C. The compositional and microstructural evolution of BYZ thin films obtained by SP-GNP is investigated as a function of several technique parameters such as precursor concentration, solvent properties and substrate properties. A microstructural evolution from porous to dense in BYZ thin films by changing precursor composition is demonstrated. This intermediate temperature technique may allow for a deeper insight into the properties of refractory complex oxides through incorporation of novel dopants and may lead to the emergence of new applications for these materials.<br>Engineering and Applied Sciences - Applied Physics
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Pecunia, Vincenzo. "Solution-based polymeric/metal-oxide thin-film transistors and complementary circuits." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708401.
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REMONDINA, JACOPO. "Ga-rich oxide-in-oxide glass ceramics: from bulk to thin film devices." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2020. http://hdl.handle.net/10281/263429.
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In questa tesi presento il lavoro da me svolto durante il mio dottorato su film vetro-ceramici nanostrutturati contenenti ossido di gallio riguardo alla possibile uso di questa classe di materiali in geometria planare all’interno di dispositivi optoelettronici. Negli ultimi tre anni, le mie ricerche sono state rivolte alla comprensione della relazione fra la presenza delle nanostrutture – analizzate attraverso uno studio strutturale dettagliato grazie a diverse tecniche di microscopia e diffrazione in funzione delle condizioni di deposizioni e trattamenti successivi – e i meccanismi fisici di trasporto di carica e polarizzazione che accadono all’interno di film di ossidi-in-ossidi.
Il materiale studiato è stato preparato tramite sputtering a radiofrequenze a partire da un precursore vetroso contenente ossidi di Li, Na, Si, Ga e Ge. Come conseguenza del processo di deposizione abbiamo ottenuto un materiale parzialmente cristallino con nanocristalli ricchi in Ga incorporati nel resto della matrice amorfa. Attraverso la microscopia a forza atomica, la riflessione dei raggi x, la diffrazione 2D dei raggi x, la dispersione 2D dei raggi x a piccoli angoli – anche usando luce di sincrotrone – abbiamo completamente caratterizzato i film nanostutturati a diverse scale di grandezza, da pochi nm a qualche micron. L’analisi dettagliata dei risultati mostra la formazione di molteplici nanocristalli anisotropi di spinello di ossido di gallio con dimensioni di 3 nm, che formano aggregati lenticolari di dimensioni maggiori con differenze significative nelle dimensioni nel piano e fuori dal piano. Come risultato dell’indagine di campioni trattati differentemente, lo studio ha inoltre mostrato che la distribuzione e la morfologia di nanostrutture può essere controllata dalle condizioni della deposizione, dalla durata e dalla temperatura del trattamento termico seguente.
Partendo dalla conoscenza delle caratteristiche strutturali, l’attività di ricerca è stata indirizzata verso l’approfondita comprensione delle proprietà di trasporto di carica risultanti dalla natura nanostrutturata del materiale, inclusa la nanofase in Ga2O3 semiconduttore e la matrice ospite dielettrica. La risposta elettrica – analizzata con l’aiuto della spettroscopia di impedenza complessa – si è rivelata essere la risultante di molteplici meccanismi di trasporto e di carica dovuti a matrice e nanofase, incluse le interfacce interne. I dati suggeriscono che il trasporto di carica è supportato da una combinazione di meccanismi attivati termicamente per hopping e per effetto tunnel mediati da un percorso di percolazione costruito dalle caratteristiche nanostrutturali del materiale. Curiosamente, la risposta nel suo complesso ha fornito indizi preliminari di plasticità elettrica, rendendo i film sottili nano-vetroceramici dei promettenti candidati come sistemi chiave in dispositivi avanzati per memorie completamente inorganiche ossido-in-ossido ispirate al cervello umano.<br>In this thesis I present the work I have carried out during my PhD on Ga-oxide containing nanostructured glass-ceramic films as a potential breakthrough for the implementation of this class of material in planar geometry for applications in the field of optoelectronics. In the last three years, my investigations have been aimed at understanding the relationship between the occurrence of nanostructuring – analysed through a detailed structural studies by means of different microscopy and diffractometric techniques as a function of deposition conditions and post-deposition treatments – and the physical mechanisms of charge transport and polarization taking place in oxide-in-oxide films.
The studied material was produced by RF sputtering deposition starting from a glass target of Li, Na, Si, Ga and Ge mixed oxide. As a consequence of the deposition process we have obtained partially crystallized material with Ga-rich nanocrystals incorporated in the remaining amorphous matrix. Through atomic force microscopy, x-ray reflectivity, 2D-x-ray diffraction, 2D-small angle x-ray scattering - also employing synchrotron radiation facilities - we have fully characterized the nanostructured films at different length scales, from few nm to few microns. The detailed analysis of the results shows the formation of multiple anisotropic spinel Ga-oxide nanocrystals with size of about 3 nm, forming larger lenticular aggregates with significant differences between the in-plane and the out-of-plane dimensions. As a result of the investigation of differently treated samples, the study also shows that size distribution and morphology of the nanostructures can be controlled by deposition conditions, duration and temperature of post-deposition thermal treatments.
Starting from the knowledge of the structural features, the research activity has been directed to the deep understanding of the charge transport properties resulting from the nanostructured nature of the material, including the Ga2O3 semiconductor nanophase and the dielectric host matrix. The electrical response – analysed with the aid of complex impedance spectroscopy – turns out to be the results of multiple contributions to transport and charging mechanisms by the matrix and the nanophase, including the effects of the internal interfaces. The data suggest that the charge transport is sustained by a combination of thermally activated hopping and tunnelling mechanisms mediated by the percolation path built up by the nanostructured features of the material. Interestingly, the overall response gives preliminary evidences of electrical plasticity, making nano-glassceramic thin films potential candidates as key systems in advanced devices for brain-inspired oxide-in-oxide fully inorganic memories.
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Huang, Yi-Wen, and 黃怡雯. "Low-Temperature Reduction of Thin Graphene Oxide Film." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/35869832541255533902.
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碩士<br>國立中央大學<br>化學工程與材料工程學系<br>103<br>The graphene oxide nanoparticles obtained from anodic graphite by electrochemical exfoliation, followed by electrophoretic deposition onto stainless steel or nickel substract. Another way to deposit graphene particles on non-conductive substract is used to produce graphene film, which named Evaporative Deposition(ED). By ED, graphene films can be deposit on polymer substracts like PEN and formed a flexible graphene film. The graphite film formed was reduced in two ways, vacuum treatment with heating up to 100℃ and ethanol treatment with heating up to 220℃. The wetting properties are determined by contact angle measurement. The advancing and receding contact angles of graphene oxide film are 38.4° and 15.5o, respectively. This result reveals the thin film is rather hydrophilic. After the reduction treatment, the advancing and receding contact angle increased to 83.1° and 50.5°, respectively, indicating that the surface of graphene oxide film becomes more hydrophobic. By the analysis of TGA, Raman, XRD and XPS, the results proved that both of the reduction treatment had attained a reduction effect. After the reduction, a graphene film was obtained and the resistivity of the film is 9×10^(-4) Ω∙cm.
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Wang, Guan-Ying, and 王冠穎. "Preparation of Thin Film with Reduced Graphene Oxide." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/f6fc74.
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碩士<br>逢甲大學<br>化學工程學系<br>107<br>In order to improve the interface situation that might be encountered in producing multi-layer structured device, a method using graphene oxide (GO) undergoes modification, adsorption and chemical reduction of was proposed in this study to prepare electrically conducting graphene thin films. Modified GO is able to enhance the adhesion between adjacent two layers of different materials when it is deposited as an interfacial layer.
First we used a large amount of oil-water interface to graft long-chain alkyl groups to one side of GO by amidaion reaction of the -COOH groups (carboxyl group) on GO and the -NH2 groups (amine group) of dodecylamine, resulting in planar GO surfactant (GO-SFT). Second, the -OH groups (hydroxyl groups) out of hydrolysis of the silane coupling agent condensed with other wardly, -OH groups of its kind and with those on the ITO glass. The long-chain alkyl groups of silane making the face out making the surface hydrophobic. Third, the GO-SFT is dissolved in water with the hydrophobic substrate immersed. The hydrophobic ends of the GO-SFT were fused with those on the surface so that the hydrophilic ends of GO-SFT face outwardly. Finally, using aqueous hydrazine solution, the hydrophilic functional groups of GO-SFT were removed, rendering reduced GO (RGO), which enhanced the electrical conductance of the adsorbed layer of graphene conductivity is increased.
It was found in previous study that GO-SFT possesses a critical micelle concentration (CMC) in aqueous solution, indicating that it can form micelles in water and change the surface tension. In this study, we successfully adsorbed GO-SFT onto a hydrophobic surface, reduced to RGO, and created a large-area conductive thin film of graphene.
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Yang, Chang-Ying, and 楊長穎. "Large area graphene – cobalt manganese oxide thin film for oxygen evolution reaction." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/14084524668459287138.
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碩士<br>國立中山大學<br>化學系研究所<br>104<br>It is necessary to develop clean and green energy because of the shortage of non-renewable energy. The hydrogen and oxygen generated by water splitting is one of the solution for clean energy. However, energy required for water splitting is usually greater than energy generated by water splitting. Oxygen evolution reaction (OER) is the main reason of excessive energy consumption in the splitting process, thus it is necessary to prepare a catalyst to promote the OER. In this research, by a simple redox method with heating, we successfully synthesized cobalt manganese oxide hydroxide (CMOH) catalyst. This method is fast and simple; efficiently deposit catalytic thin film on large area substrate even on complex surfaces.
At first, we used cobalt sulfate as precursor to prepare catalytic films (CMOH-sulfate, CMOH-S) for electrochemical measurement. However, the films (CMOH-acetate, CMOH-A) prepared by cobalt acetate have superior optical properties to CMOH-S, so we chose cobalt acetate for subsequent experiments. To further understand the difference between CMOH-S and CMOH-A, We characterized these two thin film by a series of characterization. The results of UV-visible and AFM show that the thickness of CMOH-A is smaller than CMOH-S thus has higher transmittance. CMOH-A have transmittance of 87.15% with thickness of 60 nm versus CMOH-S having 60.39% transmittance and 120 nm thickness. We further confirmed the thickness of CMOH-A to be 5 to 10 nm by TEM (rather than 60 nm by AFM), and the composition is amorphous. Despite the difference on optical property, CMOH-S and CMOH-A exhibit almost the same on OER activity. To study the reason, we altered the length of CMOH-A films, knowing that the active sites actually lie at the interface of catalyst and FTO glass.
Finally, after covering a layer of graphene on the catalytic thin films and go through 500ºC calcination under Ar, we tremendously raise the stability of OER catalyzing process, with only 7.6% decay of current after 3000 circles scanning and still remain at same over potential (0.47 V at 10 mA cm-2).
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Liu, Ding-Kun, and 劉定坤. "Preparation of silk nanofibril/graphene oxide thin film nanocomposite membrane for nanofiltration." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/scxae2.
Full textAbstract:
碩士<br>中原大學<br>化學工程研究所<br>106<br>In this study, silk nanofibril(SNF) is used as main material of nanofiltration membrane. After fibrilling and crystallizing, silk fibroin(SF) transfer itself to SNF. SNF is pressure-filtrated on HPAN substrate to form composite membrane.
FT-IR, TGA and DSC were chosen to characterize the fine structure and obtain the most cocoon-like fine structure which make it have the best performance compared to the rest SF membrane. UV-vis was used for solubility test of SFs and SNF. Surface properties and NF tests of SNF composite membrane and SNF/GO nanocomposite membrane were obtained by SEM, XPS, W.C.A and filtration set-up respectively.
Among all of the SFs and SNF membranes, SNF have 18.55LMH of the flux and 86.15% of the rejection for Na2SO4 due to its hydrophilic crystal structure. The flux gets twice and the rejection is fixed after 5% GO addition. Furthermore, SNF/GO nanocomposite membrane have at least 94% of rejection for negatively charged organic dyes.
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Khan, Mustaque Ali. "Efficient Photodetectors Based on Reduced Graphene Oxide." Thesis, 2016. https://etd.iisc.ac.in/handle/2005/4379.
Full textAbstract:
Chapter 1: In chapter 1, we have presented a brief introduction on photodetector and its various applications.
Chapter 2: Chapter 2 is the discussion about experimental methods and characterization tools. In this chapter, we have briefly discussed the experimental methods we have used for preparation of our materials. Then, we have discussed the characterization techniques we have used to characterize our prepared materials.
Chapter 3: We have prepared graphene oxide thin film by spin coating. Then, we have reduced it by hydrazine vapour to obtain reduced graphene oxide thin film. We have studied the photodetection properties of reduced graphene oxide thin film.
Chapter 4: Recently, there is a surge of preparation methods for reduced graphene oxide. But most of the times, many of its properties are not explored. In this chapter, we have explored infrared photodetection properties of metal reduced graphene oxide.
Chapter 5: In chapter 5, we have shown enhanced infrared photodetection by solvothermal reduced graphene oxide. Responsivity values of our photodetectors are comparable with many graphene-based photodetectors.
Chapter 6: We have presented our work on highly responsive infrared detector based on reduced graphene oxide in chapter 6. We have studied infrared detection by our photodetectors. We have done experiment to find out the bolometric contribution to the photocurrent.
Chapter 7: Ultraviolet photodetection by ZnO-nanosheets-decorated reduced graphene oxide has been studied in this chapter. ZnO-nanosheets film shows very less UV photo response. In case of reduced graphene oxide current value decreases during UV illumination. But, after drop casting ZnO-nanosheets on reduced graphene oxide film significant enhancement in photocurrent has been observed.
Chapter 8: This chapter is about summary of research works and future works.
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Zhan, Hao-Zhong, and 詹皓仲. "The Affect of Different Reducing Conditions on Graphene Oxide Thin Film Semiconductor Characteristics." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/61507988147736173449.
Full textAbstract:
碩士<br>國立中正大學<br>機械工程學系暨研究所<br>101<br>This thesis aims to analyze the structural characteristics of the graphene oxide (GO) with different degree of reduction by heating with various temperatures (from27℃ to 500℃) in a high vacuum (3 ~ 5 x10-6 torr) and different thickness are investigated.First, the use of graphene oxide aqueous of solution process is formed in two different film thickness by two ways: (1) Dip-coating, about 20 nm and (2) Spin-coating, about 1 ~ 5 nm. The reduced GO thin films were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy and electrical transport measurements, respectively.
The electrical measurements indicated that the mobility of thick film can improve about 2~4 order after thermal reduction. Moreover, it is observed that GO FET devices show p-type semiconducting behavior before reduction but when the same device is tested after the thermal reduction at 300℃, it shows n-type semiconducting behavior. However, it just only observed at thick films, the thinner films always shows p-type semiconducting even when the reducing temperature rise to 500℃.
The effect of high-temperature on the functional groups of GO film is evidently examined using X-ray photoelectron spectroscopy and Raman spectroscopy. The results indicated that the thick film can effectively remove the oxygen-containing functional groups by observed the atomic oxygen-to-carbon (O/C) ratio from 2.78 decrease to 0.88 and restore its graphic structure compared to the thinner film from 3.01 decrease to 1.86. The Raman measurements show that the G and 2D peaks have different doping dependence to check the behavior of GO.
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Chiang, Ju-Yun, and 姜如芸. "Feasibility of Polydopamine/Graphene Oxide Thin-Film Composite Membrane for Forward Osmosis Application." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/33tsea.
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碩士<br>國立清華大學<br>材料科學工程學系<br>105<br>In pursuance of addressing the global water shortage problem, this work was designed to fabricate carbon materials-based forward osmosis thin-film composite (FO-TFC) membranes with high flux and high salt rejection properties. In this study, a novel method has been developed which was conducted by coating the surface of a reduced graphene oxide (rGO) modified poly(ethylene terephthalate) (PET) nonwoven fabric with polydopamine/graphene oxide (PDA/GO) prior to the interfacial polymerization of trimesoyl chloride (TMC) and m-phenylenediamine (MPD).
Results showed that coating of the PDA/GO layer on the front-side of PET nonwoven substrate facilitated the formation of a denser selective polyamide（PA）layer during interfacial polymerization process to reduce reverse salt flux; the PDA/GO layer on the back-side of PET nonwoven endowed the substrate with catechol and ethylamino groups to enhance the hydrophilicity, which result in an increase in water flux. The TFC membranes fabricated by coating rGO on Ahlstrom 3324 PET nonwoven surfaces followed by coating of PDA/GO (with 80 μg/ml GO) and interfacial polymerization of PA showed a highest water flux of 3.64 LMH and the Ahlstrom 3254 PET nonwoven with same procedure demonstrated a lowest reverse salt flux 0.77 gMH in static FO test using deionized water as the feed along with 1 M NaCl draw solution in the FO mode. It showed that the feasibility of this novel method to fabricate FO-TFC membrane with good properties.
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"Synthesis and Characterization of Thionated Reduced Graphene Oxides and Their Thin Films." Doctoral diss., 2013. http://hdl.handle.net/2286/R.I.21014.
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abstract: Thiol functionalization is one potentially useful way to tailor physical and chemical properties of graphene oxides (GOs) and reduced graphene oxides (RGOs). Despite the ubiquitous presence of thiol functional groups in diverse chemical systems, efficient thiol functionalization has been challenging for GOs and RGOs, or for carbonaceous materials in general. In this work, thionation of GOs has been achieved in high yield through two new methods that also allow concomitant chemical reduction/thermal reduction of GOs; a solid-gas metathetical reaction method with boron sulfides (BxSy) gases and a solvothermal reaction method employing phosphorus decasulfide (P4S10). The thionation products, called "mercapto reduced graphene oxides (m-RGOs)", were characterized by employing X-ray photoelectron spectroscopy, powder X-ray diffraction, UV-Vis spectroscopy, FT-IR spectroscopy, Raman spectroscopy, electron probe analysis, scanning electron microscopy, (scanning) transmission electron microscopy, nano secondary ion mass spectrometry, Ellman assay and atomic force microscopy. The excellent dispersibility of m-RGOs in various solvents including alcohols has allowed fabrication of thin films of m-RGOs. Deposition of m-RGOs on gold substrates was achieved through solution deposition and the m-RGOs were homogeneously distributed on gold surface shown by atomic force microscopy. Langmuir-Blodgett (LB) films of m-RGOs were obtained by transferring their Langmuir films, formed by simple drop casting of m-RGOs dispersion on water surface, onto various substrates including gold, glass and indium tin oxide. The m-RGO LB films showed low sheet resistances down to about 500 kΩ/sq at 92% optical transparency. The successful results make m-RGOs promising for applications in transparent conductive coatings, biosensing, etc.<br>Dissertation/Thesis<br>Ph.D. Chemistry 2013
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Chen, Yi-Shiang, and 陳奕翔. "Preparation and characterization of MnOx/graphene oxide nanocomposite thin films." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/38751880443947495543.
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碩士<br>大同大學<br>材料工程學系(所)<br>101<br>This research mainly manganese oxide / graphene oxide as a composite material, the use of graphene oxide with high specific surface area in order to enhance the reaction of manganese oxide. Scan using SEM EDS mapping graphene oxide of manganese in the distribution of the surface, namely that the addition of potassium permanganate different weight ratio will be 125% coverage is wide. The XRD and EPR, respectively, adding that the high proportion of potassium permanganate is obtained when a larger proportion of manganese (IV) and capacitance value is higher.
Add different weight ratios of carbon black with different weight ratios of potassium permanganate prepared electrode potentiostat (Jiehan 500 electrochemical workstation) for cyclic voltammetry tests find its capacitance value. The results showed that the addition of different weight ratio of 40% to 100% of carbon black and potassium permanganate test strip has a higher capacitance value 58.809 F / G.
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Lee, Chun-Yuan, and 李浚源. "Properties of graphene thin films derived from high temperature reduced graphene oxide/polyethylene glycol." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/39346699920515877541.
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碩士<br>中原大學<br>化學研究所<br>100<br>Graphene with fast electron mobility, high mechanical strength, high conductivity and transparent characteristics, therefore, becomes very wide applications in electronic components.
In this study, graphene was reduced from graphene oxide (GO) by using Hummer’s methods. By adding commercially available polyethylene glycol (PEG) with molecular weight 600, 6000, 20000, and 35000 for slurry formation, we developed the graphene films on glass substrate with good conductivity for electrode applications. The characteristics of graphene/PEG films were studied by using SEM, UV-vis, four proble point conductivity measurement, Raman spectroscopy, and AFM.
It was found that PEG with molecular weight around 600~6000 is a better choice for the formation of graphene film on glass substrate in term of conductivity and their trasparancy.
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Akther, Nawshad. "Development of Thin-Film Composite Membranes Incorporated With Graphene Oxide and Derivatives for Forward Osmosis Processes." Thesis, 2020. http://hdl.handle.net/10453/149327.
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University of Technology Sydney. Faculty of Engineering and Information Technology.<br>Graphene oxide (GO) has been used to improve the anti-fouling and separation performance of the thin-film composite (TFC) membranes. Nonetheless, very few studies provided an in-depth explanation of the possible interaction between GO and polymer matrix that alter the membrane properties and performance. Thus, the overall aim of this study was to develop high-performance GO-based polyamide (PA) TFC forward osmosis (FO) membranes by systematically investigating the effect of GO and its derivatives on the modified membranes. First, polyvinyl alcohol (PVA)/GO hydrogel was coated on the PA surface to improve the membrane anti-fouling property. Second, the GO flake’s lateral size was reduced to decrease PA defects and improve membrane performance. Next, Aquaporin was added with GO in the PA layer to improve the membrane selectivity as Aquaporin healed the non-selective PA defects created by the GO flakes. Finally, the effect of GO quantum dots (GQDs) on the interfacial polymerization (IP) reaction and membrane performance at both macroscopic and microscopic levels was investigated both experimentally and using molecular dynamics (MD) simulation. GQDs decreased the IP reaction rate by reducing the diffusivities of PA monomers, reduced water permeability by acting as barriers to water molecules when present at a high concentration near the PA surface, and formed non-selective voids at the PA layer when present at very high loading.
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YANG, CHIH-PENG, and 楊志鵬. "Characteristics of Graphene-oxide Thin Film and its Bi-layer Structure for Resistance Random Access Memory Applications." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/n7d569.
Full textAbstract:
碩士<br>國立高雄應用科技大學<br>電子工程系碩士班<br>104<br>Graphene has many advantageous properties and it has been studied for many applications. Because of process integration and various promising properties, graphene oxide (GO) also attracts much interest. This thesis investigated graphene oxide for applications of resistive random access memory (RRAM). The GO film also stacked on a SiO2 layer to be a bi-layer structure for RRAM applications. The GO RRAM device can be inversely switched by dc voltages and the related characteristics were also investigated. In addition, the influence of water vapor on the GO RRAM devices were also investigated. The first part, Al/GO/Al structure was investigated. This structure shows non-polar resistive switching behavior. However, there is some difference between the resistive switching behaviors in different polarities. Due to the process procedures, interface layer is thicker in the bottom electrode than in the top electrode. Therefore, the interface layer in the bottom electrode can store less oxygen ions than the interface layer in the top electrode; thus, the resistive switching in the negative polarity is poorer than in the positive polarity. The resistive switching in the positive polarity shows smaller switching variation, and better switching reliabilities such as long retention (>10^4 s) and good endurance (>10^3 cycles). The second part investigated the resistive switching properties of Cu/GO/SiO2/Pt structure in air. The GO film with layer structure and defects can limit Cu diffusion and thus improved the switching stability. The Cu/GO/SiO2/Pt structure has more stable resistive switching behavior than the Cu/SiO2/Pt structure. The Cu/GO/SiO2/Pt structure has long retention (>10^4 s) and good endurance (>3x10^3 cycles). The third part investigated the resistive switching properties of Cu/GO/SiO2/Pt structure in N2. Water vapor assists Cu ionization procedure from the Cu electrode into SiO2 layer. Therefore, the Cu/SiO2/Pt structure can resistively switch in air, but can not switch in N2. The GO film has lots of oxygen-related groups and thus it can help the Cu ionization in N2. Thus, the Cu/GO/SiO2/Pt structure can stably switch in N2 and also has good memory reliability.
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Thomas, Rajesh. "Investigations on Graphene/Sn/SnO2 Based Nanostructures as Anode for Li-ion Batteries." Thesis, 2013. http://etd.iisc.ac.in/handle/2005/3460.
Full textAbstract:
Li-ion thin film battery technology has attracted much attention in recent years due to its highest need in portable electronic devices. Development of new materials for lithium ion battery (LIB) is very crucial for enhancement of the performance. LIB can supply higher energy density because Lithium is the most electropositive (-3.04V vs. standard hydrogen electrode) and lightest metal (M=6.94 g/mole). LIBs show many advantages over other kind of batteries such as, high energy density, high power density, long cycle life, no memory effect etc. The major work presented in this thesis is on the development of nanostructured materials for anode of Li-ion battery. It involves the synthesis and analysis of grapheme nanosheet (GNS) and its performance as anode material in Li ion battery. We studied the synthesis of GNS over different substrates and performed the anode studies. The morphology of GNS has great impact on Li storage capacity. Tin and Tin oxide nanostructures have been embedded in the GNS matrix and their electrochemical performance has been studied.
Chapter 1 gives the brief introduction about the Li ion batteries (LIBs), working and background. Also the relative advantages and characterization of different electrode materials used in LIBs are discussed.
Chapter 2 discusses various experimental techniques that are used to synthesize the electrode materials and characterize them.
Chapter3 presents the detailed synthesis of graphene nanosheet (GNS) through electron cyclotron resonance (ECR) microwave plasma enhanced chemical vapor deposition (ECR PECVD) method. Various substrates such as metallic (copper, Ni and Pt coated copper) and insulating (Si, amorphous SiC and Quartz) were used for deposition of GNS. Morphology, structure and chemical bonding were analyzed using SEM, TEM, Raman, XRD and XPS techniques. GNS is a unique allotrope of carbon, which forms highly porous and vertically aligned graphene sheets, which consist of many layers of graphene. The morphology of GNS varies with substrate.
Chapter 4 deals with the electrochemical studies of GNS films. The anode studies of GNS over various substrates for Li thin film batteries provides better discharge capacity. Conventional Li-ion batteries that rely on a graphite anode have a limitation in the capacity (372 mAh/g). We could show that the morphology of GNS has great effect in the electrochemical performance and exceeds the capacity limitation of graphite. Among the electrodes PtGNS shown as high discharge capacity of ~730 mAh/g compare to CuGNS (590 mAh/g) and NiGNS (508 mAh/g) for the first cycle at a current density of 23 µA/cm2. Electrochemical impedance spectroscopy provides the various cell parameters of the electrodes.
Chapter 5 gives the anodic studies of Tin (Sn) nanoparticles decorated over GNS matrix. Sn nanoparticles of 20 to 100nm in size uniformly distributed over the GNS matrix provides a discharge capacity of ~1500 mAh/g mAh/g for as deposited and ~950 mAh/g for annealed Sn@GNS composites, respectively. The cyclic voltammogram (CV) also shows the lithiation and delithiation process on GNS and Sn particles.
Chapter 6 discusses the synthesis of Tinoxide@GNS composite and the details of characterization of the electrode. SnO and SnO2 phases of Tin oxide nanostructures differing in morphologies were embedded in the GNS matrix. The anode studies of the electrode shows a discharge capacity of ~1400 mAh/g for SnO phase (platelet morphology) and ~950 mAh/g for SnO2 phase (nanoparticle morphology). The SnO phase also exhibits a good coulumbic efficiency of ~95%.
Chapter 7 describes the use of SnO2 nanowire attached to the side walls of the GNS matrix. A discharge capacity of ~1340 mAh/g was obtained. The one dimensional wire attached to the side walls of GNS film and increases the surface area of active material for Li diffusion. Discharge capacity obtained was about 1335 mAhg-1 and the columbic efficiency of ~86% after the 50th cycle.
The research work carried out as part of this thesis, and the results have summarized in chapter 8.
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Thomas, Rajesh. "Investigations on Graphene/Sn/SnO2 Based Nanostructures as Anode for Li-ion Batteries." Thesis, 2013. http://etd.iisc.ernet.in/2005/3460.
Full textAbstract:
Li-ion thin film battery technology has attracted much attention in recent years due to its highest need in portable electronic devices. Development of new materials for lithium ion battery (LIB) is very crucial for enhancement of the performance. LIB can supply higher energy density because Lithium is the most electropositive (-3.04V vs. standard hydrogen electrode) and lightest metal (M=6.94 g/mole). LIBs show many advantages over other kind of batteries such as, high energy density, high power density, long cycle life, no memory effect etc. The major work presented in this thesis is on the development of nanostructured materials for anode of Li-ion battery. It involves the synthesis and analysis of grapheme nanosheet (GNS) and its performance as anode material in Li ion battery. We studied the synthesis of GNS over different substrates and performed the anode studies. The morphology of GNS has great impact on Li storage capacity. Tin and Tin oxide nanostructures have been embedded in the GNS matrix and their electrochemical performance has been studied.
Chapter 1 gives the brief introduction about the Li ion batteries (LIBs), working and background. Also the relative advantages and characterization of different electrode materials used in LIBs are discussed.
Chapter 2 discusses various experimental techniques that are used to synthesize the electrode materials and characterize them.
Chapter3 presents the detailed synthesis of graphene nanosheet (GNS) through electron cyclotron resonance (ECR) microwave plasma enhanced chemical vapor deposition (ECR PECVD) method. Various substrates such as metallic (copper, Ni and Pt coated copper) and insulating (Si, amorphous SiC and Quartz) were used for deposition of GNS. Morphology, structure and chemical bonding were analyzed using SEM, TEM, Raman, XRD and XPS techniques. GNS is a unique allotrope of carbon, which forms highly porous and vertically aligned graphene sheets, which consist of many layers of graphene. The morphology of GNS varies with substrate.
Chapter 4 deals with the electrochemical studies of GNS films. The anode studies of GNS over various substrates for Li thin film batteries provides better discharge capacity. Conventional Li-ion batteries that rely on a graphite anode have a limitation in the capacity (372 mAh/g). We could show that the morphology of GNS has great effect in the electrochemical performance and exceeds the capacity limitation of graphite. Among the electrodes PtGNS shown as high discharge capacity of ~730 mAh/g compare to CuGNS (590 mAh/g) and NiGNS (508 mAh/g) for the first cycle at a current density of 23 µA/cm2. Electrochemical impedance spectroscopy provides the various cell parameters of the electrodes.
Chapter 5 gives the anodic studies of Tin (Sn) nanoparticles decorated over GNS matrix. Sn nanoparticles of 20 to 100nm in size uniformly distributed over the GNS matrix provides a discharge capacity of ~1500 mAh/g mAh/g for as deposited and ~950 mAh/g for annealed Sn@GNS composites, respectively. The cyclic voltammogram (CV) also shows the lithiation and delithiation process on GNS and Sn particles.
Chapter 6 discusses the synthesis of Tinoxide@GNS composite and the details of characterization of the electrode. SnO and SnO2 phases of Tin oxide nanostructures differing in morphologies were embedded in the GNS matrix. The anode studies of the electrode shows a discharge capacity of ~1400 mAh/g for SnO phase (platelet morphology) and ~950 mAh/g for SnO2 phase (nanoparticle morphology). The SnO phase also exhibits a good coulumbic efficiency of ~95%.
Chapter 7 describes the use of SnO2 nanowire attached to the side walls of the GNS matrix. A discharge capacity of ~1340 mAh/g was obtained. The one dimensional wire attached to the side walls of GNS film and increases the surface area of active material for Li diffusion. Discharge capacity obtained was about 1335 mAhg-1 and the columbic efficiency of ~86% after the 50th cycle.
The research work carried out as part of this thesis, and the results have summarized in chapter 8.
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Kun-ChinHsieh and 謝坤晉. "Effect of Annealing Treatment on Thin Film Microstructure, Electrical and Optical Properties in the Indium Gallium Zinc Oxide/Titanium/Graphene/Polyimide Composite Films." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/u7x3pe.
Full textAbstract:
碩士<br>國立成功大學<br>機械工程學系<br>105<br>This thesis use CVD method to create high quality graphene. First, we investigate graphene quality by Raman Analysis, Four-Point Probe and microstructure analyses. After a long test, we have made a high quality single-layer graphene successfully, and use the wetting transfer method to transfer this graphene to polyimide substrate. At last, depositing Ti and IGZO on graphene/polyimide to prepare a composite film by Magnetron Sputter.
The results show that the sheet resistance of the samples with the graphene film is 10 times lower than that the samples without graphene. In addition, the carrier mobility also increased significantly, the results show that the use of graphene will elevate the carrier mobility by 30 to 60%. The application of nano-indentation system was found that the deposition of graphene can make a substantial rise in overall hardness about 60%.
In this experiment, the oxygen content of samples was measured at room temperature and 100 ℃, 200 ℃ and 300 ℃ for 1 hour. It was found the IRO2 increased and internal residual stress was lower by increasing the annealing temperature. The increase of oxygen vacancies and the decrease of residual stress can improve the electrical properties of the film greatly. The carrier mobility of the film increases and the resistivity of the film decreases significantly.
The results show that the addition of a layer of titanium increases the electrical properties of the thin film and the adhesion between the IGZO layer and the PI substrate and improve the electrical properties of IGZO. Besides, Annealing treatment affects the transmittance of the film. When the annealing temperature increases, the crystallinity of the film becomes stronger and the lattice arrangement is neater.
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Chen, Wei-Chun, and 陳崴群. "Influence of concentration of reduced graphene oxide on properties of sol-gel prepared Al-doped Zinc oxide thin films." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/3upq2s.
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碩士<br>國立中興大學<br>光電工程研究所<br>101<br>The addition of reduced graphene oxide (RGO) to aluminum doped zinc oxide was studied and analysis conducted on film for its electrical and optical characteristics. Sol-gel was applied in a circular pattern on glass substrate with the weight concentration of 0.0 wt%, 1.0 wt%, 1.5 wt% and 3.0 wt% as the proportion of mixing. A gaseous mixture of Ar:H2=9:1 was passed through furnace pipe and the substrate was annealed in 500℃ for an hour. In electric measurement, the resistivity was 1.11ⅹ10-1 Ω-cm for RGO-free AZO film, and the lowest resistivity was 8.11ⅹ10-3 Ω-cm with RGO at 1.0 wt%. For optical analysis, when 1.0 wt% of RGO is added, the transmittance of AZO film dropped from 92% without addition to 81% with addition.The experiment showed that RGO absorbed part of visible light and thus reduced the transmittance of AZO film.
When analyzing surface measurement using a scanning electron microscope(SEM), it clearly showed that the RGO particles were distributed evenly across the surface of AZO film. The composition analysis using energy dispersive spectrometer (EDS) revealed carbon content in the AZO film, demonstrating that RGO was mixed effectively in the sol-gel. In the X-ray diffraction (XRD) analysis, the increase of RGO mixing concentration contributed to the increasing grain size of crystals on the surface. When mixing to 3.0 wt%, the 2θ angle of refraction peak shifted to the right from 34.42° with no mixing to 34.4°. It showed that the different mixing proportions of RGO at various concentrations had influence on the distribution of crystalline structure of the film.
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Zbeda, Salma Gumaa Amar. "Multilayer graphene modified metal film electrodes for the determination of trace metals by anodic stripping voltammetry." 2013. http://hdl.handle.net/11394/3802.
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Magister Scientiae - MSc<br>In this study multilayer graphene nanosheets was synthesize by oxidizing graphite to graphene oxide using H2SO4 and KMnO4 followed by reduction of graphene oxide to graphene using NaBH4. The graphene nanosheets were characterized by Fourier Transform Infrared (FTIR) and Raman spectroscopy, high resolution transmission electron microscopy (HRTEM), Scanning electron microscopy (SEM) and X-ray diffraction (XRD). HRTEM images showed that the multilayer graphene were obtained. The graphene was immobilized directly onto a glassy carbon electrode using the drop coating technique followed by the in situ deposition of mercury, bismuth or antimony thin films to afford graphene modified glassy carbon metal film electrodes (Gr-GC-MEs). The experimental parameters (deposition potential, deposition time, rotation speed, frequency and amplitude) were optimized, and the applicability of the modified electrode was investigated
towards the individual and simultaneous determination of Zn2+, Cd2+ and Pb2+ at the low concentration levels (μg L-1) in 0.1 M acetate buffer (pH 4.6) using square wave anodic stripping voltammetry (SWASV). The detection limits values for the Gr-GC-HgE was 0.08, 0.05 and 0.14 μg L-1 for Zn2+, Cd2+ and Pb2+, respectively. The Gr-GC-BiE the detection limits for was 0.12, 0.22 and 0.28 μg L-1 for Zn2+, Cd2+ and Pb2+ while the detection limits for the Gr-GC-SbE was 0.1, 0.3 and 0.3 μg L-1 for Zn2+, Cd2+ and Pb2+, respectively. A Gr-GCE prepared without any binding agents or metal film had detection limits for Zn2+, Cd2+ and Pb2+ of 3.9, 0.8 and 0.2 μg L-1 for Zn2+, Cd2+ and Pb2+. Real sample analysis of which was laboratory tap water was performed using the Gr-GCMEs. Only Gr-GC-HgE was sensitive enough to detect metal ions in the tap water samples at the 3ppb level whereas, the GC-BiE and GC-SbE detected the metal ions at the 10 μg L-1 to
30 μg L-1 level.
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Chiou, Chuang-Fu, and 邱創富. "Electrical and humidity sensing properties of reduced graphene oxide thin film fabricated by layer-by-layer covalently anchoring on flexible substrate." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/06803273987508265099.
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碩士<br>中國文化大學<br>化學系應用化學碩士班<br>102<br>Novel flexible humidity sensors were fabricated by layer-by-layer (LBL) covalently bonding graphene oxide (GO) to a gold electrode on a plastic substrate using a peptide chemical protocol and then reducing in-situGO film to a partially reduced GO film. The effect of the duration of reduction of GO film on the electrical and humidity propertiesof the reduced GO film was investigated. This flexible impedance-type humidity sensor exhibited a strong water resistance, a wide working range of humidities, a short response/recovery time, a weak dependence on temperature and good long-term stability. The different complex impedance plots obtained at low and high relative humidity indicated that the ions dominate the conductance of the anchored partially reduced GO film.
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Yang, You-Hao. "Processing and Gas Barrier Behavior of Multilayer Thin Nanocomposite Films." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-08-11685.
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Thin films with the ability to impart oxygen and other types of gas barrier are crucial to commercial packaging applications. Commodity polymers, such as polyethylene (PE), polycarbonate (PC) and polyethylene terephthalate (PET), have insufficient barrier for goods requiring long shelf life. Current gas barrier technologies like plasma-enhanced vapor deposition (PECVD) often create high barrier metal oxide films, which are prone to cracking when flexed. Bulk composites composed of polymer and impermeable nanoparticles show improved barrier, but particle aggregation limits their practical utility for applications requiring high barrier and transparency. Layer-by-layer (LbL) assemblies allow polymers and nanoparticles to be mixed with high particle loadings, creating super gas barrier thin films on substrates normally exhibiting high gas permeability.
Branched polyethylenimine (PEI) and poly (acrylic acid) (PAA) were deposited using LbL to create gas barrier films with varying pH combinations. Film thickness and mass fraction of each component was controlled by their combined charge. With lower charge density (PEI at pH 10 and PAA at pH 4), PEI/PAA assemblies exhibit the best oxygen barrier relative to other pH combinations. An 8 BL PEI/PAA film, with a thickness of 451 nm, has an oxygen permeability lower than 4.8 x 10^-21 cm^3 * cm/cm^2 * s * Pa, which is comparable to a 100 nm SiOx nanocoating. Crosslinking these films with glutaraldehyde (GA), 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide methiodide (EDC) or heating forms covalent bonds between PEI and/or PAA. Oxygen transmission rates (OTR) of 8 BL films crosslinked with 0.1M GA or 0.01M EDC show the best oxygen barrier at 100% RH.
Graphene oxide (GO) sheets and PEI were deposited via LbL with varying GO concentration. The resulting thin films have an average bilayer thickness from 4.3 to 5.0 nm and a GO mass fraction from 88 to 91wt%. Transmission electron microscopy and atomic force microscopy images reveal a highly-oriented nanobrick wall structure. A 10 BL PEI/GO film that is 91 nm thick, made with a 0.2 wt% GO suspension, exhibits an oxygen permeability of 2.5 x 10^-20 cm^3 * cm/cm^2 * s * Pa.
Finally, the influence of deposition time on thin film assembly was examined by depositing montmorillonite (MMT) or laponite (LAP) clays paired with PEI. Film growth and microstructure suggests that smaller aspect ratio LAP clay is more dip-time dependent than MMT and larger aspect ratio MMT has better oxygen barrier. A 30 BL PEI/MMT film made with 10 second dips in PEI has the same undetectable OTR as a film with 5 minute dips (with dips in MMT held at 5 minutes in both cases), indicating LbL gas barrier can be made more quickly than initially thought. These high barrier recipes, with simple and efficient processing conditions, are good candidates for a variety of packaging applications.
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CHEN, CHIAO-YI, and 陳喬毅. "A Study of the Electrophoretic Deposition of Graphene Oxide Thin Films in Asymmetrical AC Electric Fields." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/63tay6.
Full textAbstract:
碩士<br>大葉大學<br>醫療器材設計與材料碩士學位學程<br>106<br>In the present study, graphene oxides (GrO) were synthesized by the Modified Hummer method with natural graphite powder as the raw material. The chemical structures and the surface morphology of the as-synthesized GrO were characterized by Raman and FE-SEM, respectively where aqueous GrO dispersions were prepared by adding aliquots of alcohol as solvent. The GrO thin films were prepared by electrophoretic deposition (EPD) over Indium Tin Oxide (ITO) glass substrates in asymmetric alternating current (AAC) and direct current (DC) electric fields, respectively. A preliminary study was conduct to find the appropriate EPD operation window after which the as-deposited GrO films by different deposition duration (5, 10, 20, 30 s), at identical operation voltage and frequency were compared comprehensively to investigate the effects of various modes of electric fields on the properties of the deposited GrO films. For AAC-EPD mode, all the three common waveforms has been choose, including square wave, square wave and sine wave, respectively. The former (square wave) could be named as the unbalanced electric field whose waveform was asymmetric in which the positive and negative area of the same size. In contrast, the remaining two waveforms could not meet the requirement of unbalanced electric field, i.e., a net DC current flows toward a given electrode leading to a DC and/or pulse-DC mode-like electric field.
It shows that, compared to those deposited by DC-EPD, the deposition rate for those deposited by AAC modes were apparently much slower whereas different kind of waveform has made little difference in the rate of GrO film deposition. For those deposited by AAC-EPD with waveform of both square and sine wave, the behaver of rate increment about deposition time did follow the relationship of Hamker equation whereas the triangular wave did not show similar linear relationship. The complexity of the deposition behavior under the AAC electric fields could be attributed to the Stotz-Wien effect where the variation of electric filed strength with applied voltage were nonlinear, leading to different films structure and properties. It is noteworthy that for AAC-EPD films with square waveform, there is no hydrogen evolving on the cathode surface owing that all charges were flowed within the double layers in the vicinity of electrodes.
In summary, the best result was obtained by AAC-EPD with square waveform at 40V, 50Hz, 25% duty cycle with deposition duration of 30s under which the as-deposited GrO films has compact surface morphology with RMS surface roughness of 4.40 nm, lowest sheet resistance of 25.93 0.85(/), and optical transmittance of 84.591%. By applying AAC-EPD with waveform of sine and triangular wave, the wrinkle on film surface becomes prominent, whereas both the optical transparency and electric conductivity for the as-deposited GrO films were deteriorated accordingly which might be ascribed to the hydrogen evolution at cathode surface during the prolonging deposition process.
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WANG, YIN-YIN, and 王尹吟. "A Study on Hybrid Thin Film of Ag Nanowire and Reduced Graphene Oxide Prepared by H2-Low Damage Plasma as Flexible Transparent Electrode." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/13806060659432834588.
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