Dissertations / Theses on the topic 'Molybdenum Thin Films'
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Rickman, Sarah. "Growth and characterization of molybdenum disulfide, molybdenum diselenide, and molybdenum(sulfide, selenide) formed between molybdenum and copper indium(sulfide, selenide) during growth." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 0.94 Mb., 85 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:1435848.
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Kaye, Simon Peter. "Ion-assisted deposition of molybdenum disulphide films." Thesis, University of Salford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238835.
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Wang, Yimin. "Reactive Sputter Deposition of Molybdenum Nitride Thin Films." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1025108562.
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Gross, Carl Morris III. "Growth and Characterization of Molybdenum Disulfide Thin Films." Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1464363549.
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Cormier, Pierre Richard Sébastien. "Secondary electron emission properties of molybdenum disulfide thin films." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq31189.pdf.
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Guimond, Sebastien. "Vanadium and molybdenum oxide thin films on Au(111)." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2009. http://dx.doi.org/10.18452/15999.
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In der vorliegenden Arbeit wurden das Wachstum und die Oberflächenstruktur von definier-ten V2O3-, V2O5- und MoO3-Filmen auf Au(111) sowie deren Einsatz als Modellsysteme zur Untersuchung von Elementarreaktionen auf Vanadiumoxid- und Molybdänoxid-basierten selektiven Oxidationskatalysatoren untersucht. Im Falle von V2O3(0001) befindet sich an der Oberfläche der Filme eine Lage von Vanadylgruppen, welche kein Bestandteil der Kristall-struktur sind. Die O Atome der Vanadylgruppen können durch Elektronenbeschuss definiert entfernt werden, wodurch eine partiell oder vollständig V-terminierte Oberfläche erzeugt werden kann. Der Grad der Oberflächenreduktion wird durch die Elektronendosis festgelegt. Dieses ermöglicht eine Untersuchung des Einflusses der Vanadylgruppen und der unterkoor-dinierten V-Ionen auf die Reaktivität der Modellkatalysatoren. Die Präparation von defektar-men V2O5(001)- und MoO3(010)-Filmen ist erstmals in der vorliegenden Arbeit dokumen-tiert. Diese Filme wurden mittels Oxidation in einer Hochdruckzelle bei einem Sauerstoffdruck von 50 mbar hergestellt. Anders als in vielen Publikationen berichtet sind diese hochkristallinen Schichten unter UHV-Bedingungen weitgehend reduktionsbeständig. Oberflächenverunreinigungen und Defekte scheinen aber einen großen Einfluss auf die Redu-zierbarkeit zu haben. Die von den Strukturen der regulären Oxide abweichenden Strukturen der Koinzidenzgitter von V2O5- und MoO3-Monolagen werden durch die Wechselwirkung mit der Au(111)-Unterlage stabilisiert, was vermutlich durch die einfache Verschiebbarkeit von Koordinationseinheiten in V und Mo-Oxiden erleichtert wird. Für beide Oxide beginnt das Wachstum regulärer Oxidstrukturen erst nach Vollendung der zweiten Lage. Die für geträgerte V2O5-Katalysatoren häufig vorgebrachte Annahme, dass V2O5-Kristallkeimbildung direkt auf einer Monolage stattfindet, sollte somit mit Vorsicht betrachtet werden.The growth and the surface structure of well-ordered V2O3, V2O5 and MoO3 thin films have been investigated in this work. These films are seen as model systems for the study of ele-mentary reaction steps occurring on vanadia and molybdena-based selective oxidation cata-lysts. It is shown that well-ordered V2O3(0001) thin films can be prepared on Au(111). The films are terminated by vanadyl groups which are not part of the V2O3 bulk structure. Elec-tron irradiation specifically removes the oxygen atoms of the vanadyl groups, resulting in a V-terminated surface. The fraction of removed vanadyl groups is controlled by the electron dose. Such surfaces constitute interesting models to probe the relative role of both the vanadyl groups and the undercoordinated V ions at the surface of vanadia catalysts. The growth of well-ordered V2O5(001) and MoO3(010) thin films containing few point defects is reported here for the first time. These films were grown on Au(111) by oxidation under 50 mbar O2 in a dedicated high pressure cell. Contrary to some of the results found in the literature, the films are not easily reduced by annealing in UHV. This evidences the contribution of radiation and surface contamination in some of the reported thermal reduction experiments. The growth of ultrathin V2O5 and MoO3 layers on Au(111) results in formation of interface-specific monolayer structures. These layers are coincidence lattices and they do not correspond to any known oxide bulk structure. They are assumed to be stabilized by electronic interaction with Au(111). Their formation illustrates the polymorphic character and the ease of coordination units rearrangement which are characteristic of both oxides. The formation of a second layer apparently precedes the growth of bulk-like crystallites for both oxides. This observation is at odds with a common assumption that crystals nucleate as soon as a monolayer is formed dur-ing the preparation of supported vanadia catalysts.
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Tashiro, Hidenori. "Time-resolved infrared studies of superconducting molybdenum-germanium thin films." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0008001.
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Bragg, Donald. "Photocatalytic Oxidation of Carbon Monoxide Using Sputter Deposited Molybdenum Oxide Thin Films on a Silicon Dioxide Substrate." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/BraggD2007.pdf.
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Golub, A. S., N. D. Lenenko, E. P. Krinichnaya, O. P. Ivanova, I. V. Klimenko, and T. S. Zhuravleva. "Nanostructured Films of Semiconducting Molybdenum Disulfide Obtained Through Exfoliation-Restacking Method." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35055.
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Preparing MoS2 films in mild conditions, using deposition of suspended MoS2 nanoplatelets onto the substrate is described. For this purpose, the nanosized MoS2 particles were obtained via restacking of MoS2 single layers produced by chemical exfoliation of bulk MoS2 crystals in liquid media. X-Ray diffraction study of the films showed that the basal planes of MoS2 crystallites are mainly oriented in the plane paral-lel to the substrate. Atomic force microscopy examination revealed the dependence of the film surface to-pography, as well as the roughness characteristics on the film thickness, which varied in the range of 0.03-2.2 m. Optical absorption spectra of the obtained MoS2 films were found to contain the same absorption bands as the spectra of thin natural MoS2 single crystals. Dark conductivity of the films was determined to be ~ 10–3 S∙сm–1 at 300 K. The present MoS2 films were found to be photosensitive in the range of 300-800 nm, providing the maximum value of photocurrent under photoexcitation at ~ 440 nm.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35055
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Ashraf, Sobia. "Aerosol assisted chemical vapour deposition of tungsten and molybdenum oxide thin films." Thesis, University College London (University of London), 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.498322.
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Makous, John Lawrence. "Superconductivity in molybdenum/tantalum superlattices and yttrium-barium-copper-oxide thin films." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184662.
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The properties of sputter-deposited multilayered superconductors have been studied, including Mo/Ta metallic superlattices and thin films of YBa₂Cu₃O₇₋ₓ. The former have been prepared with the same integer number of atomic planes of Mo and Ta modulating the layered composition. In contrast to behavior observed in other metal-metal superlattices, Mo/Ta exhibits long range structural coherence and metallic resistivity behavior over the entire range of wavelengths down to the monolayer limit. The structural properties of these superlattices are used to explain an anomalous decrease in the c₄₄ elastic stiffness constant previously observed in Mo/Ta for 20 Å ≤ Λ ≤ 50 Å. Superconductivity measurements indicate "universal" T(c) versus ρ behavior in Mo/Ta, and tunneling results show that these superlattices are weakly-coupled BCS superconductors. The second part of this dissertation examines the properties of superconducting thin films of YBa₂Cu₃O₇₋ₓ prepared by dc triode sputtering from metallic targets of Y and Ba₂Cu₃. Post-depression annealing in O₂ is necessary to form the superconducting oxide. Various substrates were used, including sapphire and MgO, both with and without buffer layers of Ag, and SrTiO₃. The buffer layers are used to decrease the interaction of the substrate with the film. The best results occur with films deposited on MgO with a Ag buffer layer, exhibiting T(c) onsets as high as 90 K and zero resistance by 60 K. I find that the crystalline orientation of films deposited on (100) SrTiO₃ are influenced by the substrate, and re-annealing a sample can sometimes improve its superconducting properties. Overall, reproducibility is the biggest problem with this technique, as Ba metal is highly reactive with the environment.
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Shapiro, Arye. "Growth, structure, and electronic properties of molybdenum/silicon thin films by Molecular beam epitaxy (MBE)." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184846.
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Mo-Si thin films have proven applications in semiconductor devices and x-ray optics. Since their performance in these applications is extremely sensitive to interface roughness, it is important to understand the nucleation and growth mechanisms which affect the microscopic interface structure. Investigations of the initial stages of interface formation in the Mo-Si system were carried out by depositing fractional-monolayer Mo films onto Si(100)-(2x1) and Si(111)-(7x7) surfaces using Molecular Beam Epitaxy (MBE) with feedbackcontrolled electron-beam evaporation, and by characterizing these ultra-thin Mo films using in situ Reflection High-Energy Electron Diffraction (RHEED), LowEnergy Electron Diffraction (LEED), Auger Electron Spectroscopy (AES), and xray Photoelectron Spectroscopy (XPS). Continuous growth of multiple Mo coverages on a single Si wafer was accomplished with a technique developed for these experiments, involving a moveable substrate shutter. The coverages were corrected for the deposition profile (due to growth chamber geometry) with ex situ Rutherford Backscattering Spectroscopy (RBS) data and computer modelling. The growth mode was determined using Auger intensity measurements. In order to correct for the time dependence of the Auger intensities due to trace surface contamination and instrumental drift, a technique was developed which used Auger measurements on bulk Si and Mo to further normalize the intensity data for the fractional-monolayer coverages of Mo. The AES results in this dissertation show that for relatively slow Mo deposition (i.e. rates of approximately 0.05 Angstroms per second) onto either (100) or (111) Si substrates maintained at low temperatures (i.e. 100 °C), the first atomic monolayer of Mo is deposited in a non-layer-by-layer fashion, implying interdiffusion and/or agglomeration of the Mo overlayer. The LEED and RHEED results on similar samples show that the Mo layer is non-crystalline, i.e. there is no long-range periodicity. In addition, the deposition of Mo destroys the periodicity of the underlying Si atoms. For these deposition conditions, both the growth mode and the lack of crystallinity are independent of Si surface crystal structure.
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Trainer, Daniel Joseph. "INVESTIGATION OF THE QUASIPARTICLE BAND GAP TUNABILITY OF ATOMICALLY THIN MOLYBDENUM DISULFIDE FILMS." Diss., Temple University Libraries, 2019. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/559773.
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PhysicsPh.D.
Two dimensional (2D) materials, including graphene, hexagonal boron nitride and layered transition metal dichalcogenides (TMDs), have been a revolution in condensed matter physics and they are at the forefront of recent scientific research. They are being explored for their unusual electronic, optical and magnetic properties with special interest in their potential uses for sensing, information processing and memory. Molybdenum disulfide (MoS2) has been the flagship semiconducting TMD over the past ten years due to its unique electronic, optical and mechanical properties. In this thesis, we grow mono- to few layer MoS2 films using ambient pressure chemical vapor depositions (AP-CVD) to obtain high quality samples. We employ low temperature scanning tunneling microscopy and spectroscopy (LT-STM/STS) to study the effect of layer number on the electronic density of states (DOS) of MoS¬2. We find a reduction of the magnitude of the quasiparticle band gap from one to two monolayers (MLs) thick. This reduction is found to be due mainly to a shift of the valence band maxima (VBM) where the conduction band minimum (CBM) does not change dramatically. Density functional theory (DFT) modeling of this system shows that the overlap of the interfacial S-pz orbitals is responsible for shifting the valence band edge at the Γ-point toward the Fermi level (EF), reducing the magnitude of the band gap. Additionally, we show that the crystallographic orientation of monolayer MoS2 with respect to the HOPG substrate can also affect the electronic DOS. This is demonstrated with five different monolayer regions having each with a unique relative crystallographic orientation to the underlying substrate. We find that the quasiparticle band gap is closely related to the moiré pattern periodicity, specifically the larger the moiré periodicity the larger the band gap. Using DFT, we find that artificially increasing the interaction between the film and the substrate means that the magnitude of the band gap reduces. This indicates that the moiré pattern period acts like a barometer for interlayer coupling. We investigate the effect of defects, both point and extended defects, on the electronic properties of mono- to few layer MoS¬2 films. Atomic point defects such including Mo interstitials, S vacancies and O substitutions are identified by STM topography. Two adjacent defects were investigated spectroscopically and found to greatly reduce the quasiparticle band gap and arguments were made to suggest that they are Mo-Sx complex vacancies. Similarly, grain boundaries were found to reduce the band gap to approximately ¼ of the gap found on the pristine film. We use Kelvin probe force microscopy (KPFM) to investigate the affect of annealing the films in UHV. The work function measurements show metastable states are created after the annealing that relax over time to equilibrium values of the work function. Scanning transmission electron microscopy (STEM) is used to show that S vacancies can recombine over time offering a feasible mechanism for the work function changes observed in KPFM. Lastly, we report how strain affects the quasiparticle band gap of monolayer MoS2 by bending the substrate using a custom built STM sample holder. We find that the local, atomic-scale strain can be determined by a careful calibration procedure and a modified, real-space Lawler Fujita algorithm. We find that the band gap of MoS2 reduces with strain at a rate of approximately 400 meV/% up to a maximum strain of 3.1%, after which the film can slip with respect to the substrate. We find evidence of this slipping as nanoscale ripples and wrinkling whose local strain fields alter the local electronic DOS.
Temple University--Theses
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Giang, Hannah. "Rational Fabrication of Molybdenum Disulfide and Metal-doped Molybdenum Disulfide Thin Films via Electrodeposition Method for Energy Storage, Catalysis, and Biosensor Applications." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/dissertations/1861.
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This dissertation presents studies electrodeposited MoS2 and metal-doped MoS2 thin films, and their performance for energy storage, catalysis, and biosensor applications. Ni-doped MoS2 thin films were fabricated by electrodeposition from electrolytes containing both MoS42- and varying concentrations of Ni2+, followed by annealing at 400 ºC for 2 h in an Ar atmosphere. The film resistivity increased from 11.3 µΩ-cm for un-doped MoS2 to 32.8 µΩ-cm for Ni-doped MoS2 containing 9 atom% Ni. For all Ni dopant levels studied, only the x-ray diffraction (XRD) pattern expected for MoS2 is observed, with the average grain size increases with increasing Ni content. Ni-doped MoS2 thin films were tested for their activity towards the hydrogen evolution reaction (HER) in 0.5M H2SO4. Tafel equation fits reveal that the catalytic activity for HER, as measured by the exchange current density, increases up to 6 atom% Ni, and then decreases slightly for 9 atom% Ni. Ni-doped MoS2 thin films were also tested in 1.0 M Na2SO4 for use within electrochemical supercapacitors, and the capacitance per unit area increases by 2-3x for 9 atom% Ni-doped MoS2 relative to un-doped MoS2. The highest specific capacitance obtained for Ni-doped MoS2 during galvanostatic charge-discharge measurements is ~300 F/g
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Forsberg, Viviane. "Liquid Exfoliation of Molybdenum Disulfide for Inkjet Printing." Licentiate thesis, Mittuniversitetet, Avdelningen för naturvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-29181.
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Since the discovery of graphene, substantial effort has been put toward the synthesis and production of 2D materials. Developing scalable methods for the production of high-quality exfoliated nanosheets has proved a significant challenge. To date, the most promising scalable method for achieving these materials is through the liquid-based exfoliation (LBE) of nanosheetsin solvents. Thin films of nanosheets in dispersion can be modified with additives to produce 2D inks for printed electronics using inkjet printing. This is the most promising method for the deposition of such materials onto any substrate on an industrial production level. Although well-developed metallic and organic printed electronic inks exist on the market, there is still a need to improve or develop new inks based on semiconductor materials such as transition metal dichalcogenides (TMDs) that are stable, have good jetting conditions and deliver good printing quality.The inertness and mechanical properties of layered materials such as molybdenum disulfide (MoS2) make them ideally suited for printed electronics and solution processing. In addition,the high electron mobility of the layered semiconductors, make them a candidate to become a high-performance semiconductor material in printed electronics. Together, these features make MoS2 a simple and robust material with good semiconducting properties that is also suitable for solution coating and printing. It is also environmentally safe.The method described in this thesis could be easily employed to exfoliate many types of 2D materials in liquids. It consists of two exfoliation steps, one based on mechanical exfoliation of the bulk powder utilizing sand paper, and the other inthe liquid dispersion, using probe sonication to liquid-exfoliate the nanosheets. The dispersions, which were prepared in surfactant solution, were decanted, and the supernatant was collected and used for printing tests performed with a Dimatix inkjetprinter. The printing test shows that it is possible to use the MoS2 dispersion as a printed electronics inkjet ink and that optimization for specific printer and substrate combinations should be performed. There should also be advances in ink development, which would improve the drop formation and break-off at the inkjet printing nozzles, the ink jetting and, consequently, the printing quality.Sedan upptäckten av grafen har mycket arbete lagts på framställning och produktion av 2D-material. En viktig uppgift har varit att ta fram skalbara metoder för produktion av högkvalitativa nanosheets via exfoliering. Den mest lovande skalbarametoden hittills har varit vätskebaserad exfoliering av nanosheets i lösningsmedel. Tunna filmer av nanosheets i dispersion kan anpassas med hjälp av tillsatser och användas för tillverkning av halvledare strukturer med inkjet-skrivare, vilket är den mest lovande metoden för på en industriell produktions nivå beläggaden typen av material på substrat. Även om det finns välutvecklade metalliska och organiskabläck för tryckt elektronik, så finns det fortfarande ett behov av att förbättra eller utveckla nya bläck baserade på halvledarmaterial som t.ex. TMD, som är stabila, har goda bestryknings egenskaper och ger bra tryckkvalitet. Den inerta naturen tillsammans med de mekaniska egenskaperna som finns hosskiktade material, som t.ex. molybdendisulfid (MoS2), gör demlämpliga för flexibel elektronik och bearbetning i lösning. Dessutom gör den höga elektronmobiliteten i dessa 2D-halvledaredem till en stark kandidat som halvledarmaterial inom trycktelektronik. Det betyder att MoS2 är ett enkelt och robust material med goda halvledaregenskaper som är lämpligt för bestrykning från lösning och tryck, och är miljömässigt säker.Den metod som beskrivs här kan med fördel användas föratt exfoliera alla typer av 2D-material i lösning. Exfolieringensker i två steg; först mekanisk exfoliering av torr bulk med sandpapper, därefter används ultraljudsbehandling i lösning för att exfoliera nanosheets. De dispersioner som framställts i lösning med surfaktanter dekanterades och det övre skiktetanvändes i trycktester med en Dimatix inkjet-skrivare.Tryckprovet visar att det är möjligt att använda MoS2 -dispersion som ett inkjet-bläck och att optimering för särskildaskrivar- och substratkombinationer borde göras, såsom förbättringav bläcksammansättningen med avseende på droppbildning och break-off vid skrivarmunstycket, vilket i sin tur skulleförbättra tryckkvaliteten.
KM2
Paper Solar Cells
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Rouse, Ambrosio A. 1960. "Characterization and Field Emission Properties of Mo2C and Diamond Thin Films Deposited on Mo Foils and Tips by Electrophoresis." Thesis, University of North Texas, 1999. https://digital.library.unt.edu/ark:/67531/metadc278393/.
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Jayabal, Matheshkumar. "Molybdenum as a back contact for cucl treated cds/cdte solar cells." Scholar Commons, 2005. http://scholarcommons.usf.edu/etd/2937.
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CdTe is one of the most promising absorbers for use in inexpensive semiconductor solar cells having achieved a high efficiency of 16.4% in small area cells [1]. One of the most important technological problems in obtaining high efficiencies is to have a good ohmic contact on the CdTe, which is characterized by a very high work function [2]. Cu is used as a dopant in CdTe at the contact to promote quantum mechanical tunneling [3]. But the oversupply of Cu causes the diffusion of Cu through CdTe to the underlying CdS layer resulting in the degradation of the cell performance. It has been reported that Cu was segregated near the CdS/CdTe junction. To avoid the Cu segregation at the junction, Cu supply should be minimized while the ohmic characteristics of p-CdTe contact are maintained [4]. In this thesis, the main objective is to understand the role of Cu at the CdS/CdTe interface. Here the Cu is added at the CdS/CdTe interface and is avoided at the back contact.
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Nowrozi, Mojtaba Faiz. "A systematic study of LPCVD refractory metal/silicide interconnect materials for very large scale integrated circuits." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184396.
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Recently, refractory materials have been proposed as a strong alternative to poly-silicon and aluminum alloys as metallization systems for Very Large Scale Integrated (VLSI) circuits because of their improved performance at smaller Integrated Circuit (IC) feature size and higher interconnect current densities. However, processing and reliability problems associated with the use of refractory materials have limited their widespread acceptance. The hot-wall low pressure chemical vapor deposition (LPCVD) of Molybdenum and Tungsten from their respective hexacarbonyl sources has been studied as a potential remedy to such problems, in addition to providing the potential for higher throughput and better step coverage. Using deposition chemistries based on carbonyl sources, Mo and W deposits have been characterized with respect to their electrical, mechanical, structural, and chemical properties as well as their compatibility with conventional IC processing. Excellent film step coverage and uniformity were obtained by low temperature (300-350 C) deposition at pressures of 400-600 mTorr. As-deposited films were observed to be amorphous, with a resistivity of 250 and 350 microohm-cm for Mo and W respectively. On annealing at high temperatures in a reducing or inert atmosphere, the films crystallize with attendant reduction in resistivity to 9.3 and 12 microohm-cm for Mo and W, respectively. The average grain size also increases as a function of time and temperature to a maximum of 2500-3000 A. The metals and their silicides that are deposited, using silane as silicon source, are integratable to form desired metal-silicide gate contact structures. Thus, use of the low resistivity of the elemental metal coupled with the oxidation resistance of its silicide manifests the quality and economy of the process. MOS capacitors with Mo and W as the gate material have been fabricated on n-type (100) silicon. A work function of 4.7 +/- 0.1 eV was measured by means of MOS capacitance-voltage techniques. The experimental results further indicate that the characteristics of W-gate MOS devices related to the charges in SiO₂ are comparable to those of poly-silicon; while, the resistivity is about two orders of magnitude lower than poly-silicon. It is therefore concluded that hot-wall low pressure chemical vapor deposition of Mo and W from their respective carbonyl sources is a viable technique for the deposition of reliable, high performance refractory metal/silicide contact and interconnect structures on very large scale integrated circuits.
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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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Lim, Seong-Chu. "Scanning Tunneling Microscopy of Epitaxial Diamond (110) and (111) Films and Field Emission Properties of Diamond Coated Molybdenum Microtips." Thesis, University of North Texas, 1998. https://digital.library.unt.edu/ark:/67531/metadc279160/.
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The growth mechanism of chemical vapor deposition (CVD) grown homo-epitaxial diamond (110) and (111) films was studied using ultrahigh vacuum (UHV) scanning tunneling microscopy (STM). In addition, the field emission properties of diamond coated molybdenum microtips were studied as a function of exposure to different gases.
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Takahashi, Eigo. "Correlation between preparation parameters and properties of molybdenum back contact layer for CIGS thin film solar cells." Master's thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4554.
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Molybdenum (Mo) thin film back contact layers for thin film CuIn(subscript 1-x])Ga[subscript] xSe[sub]2 (CIGS) solar cells were deposited onto soda lime glass substrates using a direct current (DC) planar magnetron sputtering deposition technique. Requirements for the Mo thin film as a back contact layer for CIGS solar cells are various. Sheet resistance, contact resistance to the CIGS absorber, optical reflectance, surface morphology, and adhesion to the glass substrate are the most important properties that the Mo thin film back contact layer must satisfy. Experiments were carried out under various combinations of sputtering power and working gas pressure, for it is well known that mechanical, morphological, optical, and electrical property of a sputter-deposited Mo thin film are dependent on these process parameters. Various properties of each Mo film were measured and discussed. Sheet resistances were measured using a four-point probe equipment and minimum value of 0.25 [omega]/sq was obtained for the 0.6 [micro]meter-thick Mo film. Average surface roughnesses of each Mo film ranged from 15 to 26 A were measured by Dektak profilometer which was also employed to measure film thicknesses. Resistivities were calculated from the sheet resistance and film thickness of each film. Minimum resistivity of 11.9 mu [omega]cm was obtained with the Mo thin film deposited at 0.1 mTorr and 250 W. A residual stress analysis was conducted with a bending beam technique with very thin glass strips, and maximum tensile stress of 358 MPa was obtained; however, films did not exhibit a compressive stress. Adhesive strengths were examined for all films with a "Scotch-tape" test, and all films showed a good adhesion to the glass substrate.; Sputter-deposited Mo thin films are commonly employed as a back contact layer for CIGS and CuInSe[sub]2 (CIS)-based solar cells; however, there are several difficulties in fabricating a qualified back contact layer. Generally, Mo thin films deposited at higher sputtering power and lower working gas pressure tend to exhibit lower resistivity; however, such films have a poor adhesion to the glass substrate. On the other hand, films deposited at lower power and higher gas pressure tend to have a higher resistivity, whereas the films exhibit an excellent adhesion to the glass substrate. Therefore, it has been a practice to employ multi-layered Mo thin film back contact layers to achieve the properties of good adhesion to the glass substrate and low resistivity simultaneously. However, multi layer processes have a lower throughput and higher fabricating cost, and requires more elaborated equipment compared to single layer processes, which are not desirable from the industrial point of view. As can be seen, above mentioned process parameters and the corresponding Mo thin film properties are at the two extreme ends of the spectrum. Hence experiments were conducted to find out the mechanisms which influence the properties of Mo thin films by changing the two process parameters of working gas pressure and sputtering power individually. The relationships between process parameters and above mentioned properties were studied and explained. It was found that by selecting the process parameters properly, less resistive, appropriate-surfaced, and highly adhesive single layer Mo thin films for CIGS solar cells can be achieved.ID: 028916841; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.M.S.E.)--University of Central Florida, 2010.; Includes bibliographical references (p. 97-111).
M.S.M.S.E.
Masters
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Materials Science and Engineering
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Jurgens-Kowal, Teresa Ann. "Preparation and characterization of synthetic mineral surfaces : adsorption and thermal decomposition of tetraethoxysilane on magnesium oxide, molybdenum, and titanium dioxide surfaces /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/9865.
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Khatri, Himal. "New Deposition Process of Cu(In,Ga)Se2 Thin Films for Solar Cell Applications." Connect to full text in OhioLINK ETD Center, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1259612259.
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Pereira, Audrei Conti. "Eletrodos modificados com óxidos de molibdênio: caracterização e estudos eletroquímicos sobre o processo de oxidação anódica do NO." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/46/46133/tde-25092014-163727/.
Full textAbstract:
No presente trabalho a deposição eletroquímica de filmes de óxidos de molibdênio na superfície do eletrodo de carbono vítreo, sob diferentes condições experimentais, foi investigada. Maiores concentrações de Mo(VI) na solução resultaram em filmes mais espessos, com a extensão da deposição sendo dependente do pH do meio. A utilização de eletrodos modificados por estes filmes no estudo do processo de redução eletrocatalítica do iodato resultou em voltamogramas com comportamentos eletroquímicos diferentes, sugerindo a formação de filmes com composição variada. A composição destes filmes foi investigada por retroespalhamento Rutherford (RBS), onde diferentes relações entre os átomos de molibdênio e oxigênio foram detectadas. A diminuição da intensidade do sinal voltamétrico de redução do ferricianeto, em função do aumento da espessura do filme depositado na superfície do eletrodo de carbono vítreo, sugeriu que o processo catódico foi dificultado à medida que o filme se tomou mais espesso. Esta observação indicou que o processo ocorre essencialmente na superfície do eletrodo de carbono vítreo, não havendo intermediação por parte do filme. Um sistema vedado foi montado para a obtenção da solução saturada de NO, bem como células eletroquímicas especiais foram construídas para a preparação das soluções. Os voltamogramas da oxidação do NO em eletrodo com superfície polida apresentaram duas ondas, as quais foram atribuídas à formação de nitrito e à oxidação deste ânion a nitrato, respectivamente. O comportamento eletroquímico do NO também foi observado em eletrodos com superfície modificada a partir de diferentes condições de Mo(VI), observandose que o processo de oxidação anódica do NO ocorreu de maneira facilitada ao se trabalhar com O eletrodo modificado a partir de uma solução de Mo(VI) 1mmol L-1 de pH 2,5.The electrodeposition of molybdenum oxides films onto glassy carbon surfaces in several media was studied. Results showed a dependence of the thickness of the film on the Mo(VI) concentration. They also confirmed the existence of some specific pH conditions where the deposition occurred at higher extension. These modified electrodes have presented different behaviors in the electroreduction of iodate, probably due to the distinct film composition. Rutherford Backscattering Spectrometry analysis of these materiais has shown different ratios between the amount of Mo and O atoms, confirming this assumption. The electroreduction of [Fe(CN6)]-3 at the modified electrode was investigated aiming to evaluate the influence of the film porosity on the voltammetric profile of the electroative species. Data indicated that the cathodic process occurs at the glassy carbon surface by the penetration of [Fe(CN)6]-3 ions through channels in the film. Experiments with nitric oxide (NO) were carried out at a sealed electrochemical cell, which was homemade by using acrylic. The voltammetric signal of NO at a bare platinum electrode consisted of two waves, which were associated to the consecutive formation of nitrite and nitrate. The NO electrochemical behavior was also studied at modified electrodes and a current enhancement was verified by using films produced from solutions containing 1mmolL-1 of the Mo(VI), at pH 2.5.
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Ahmed, Omer. "Tribological and Mechanical properties of Multilayered Coatings." University of Toledo / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1501763970144729.
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Mittapalli, Tharun. "THIN FILM ELECTRO DEPOSITION OF MOLYBDENUM DISULFIDE FOR ENERGY STORAGE." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1816.
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Growing environmental factors like depletion of fossil fuels have given room to alternative energy technologies. Recently, attention has been focused on the development of the electrochemical capacitors with high power, which are called super capacitors for energy storage. Considering different materials and its oxides so far, ruthenium oxide, Magnesium oxide, Molybdenum sulfide, Molybdenum Oxides, Nickel Oxide has been investigated. Molybdenum oxides and sulfides have given more importance over all other materials because of its low cost, great quantity and very high capacity. Manganese oxides can exhibit various structures but it depends mainly on the methods of synthesis and post treatment procedures. Electrochemical deposition is most preferred because other methods are very expensive, due to high temperature and vacuum technology. The purpose of this study is to understand the thin film deposition mechanism of molybdenum disulfide, and to find the thickness of deposition on flat glassy carbon electrode. Most of the research studies show the capacitance of the thin film deposition on three-dimensional electrodes made from Nano particles, carbon foam, and other porous electrode materials report the charge storage capacity in units of F/g rather than F/cm2 .In this study an effort is made to understand the thin film deposition of MoS2 ( molybdenum disulfide) on flat materials like glassy carbon electrode, ITO , and gold in order to determine the fundamental basis for capacitance values reported in these different units and it was found that the MoS2 deposited on GCE has consistent capacitance about 0.009 F/cm2 after annealing the deposits
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Kadam, Ankur. "PREPARATION OF EFFICIENT CUIN1-XGAXSE2-YSY/CDS THIN-FILM SOLAR CELLS BY OPTIMIZING THE MOLYBDENUM BACK CONTACT AND USING DIETHYL." Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4230.
Full textAbstract:
High efficiency CuIn1-xGaxSe2-ySy (CIGSS)/CdS thin-film solar cells were prepared by optimizing the Mo back contact layer and optimizing the parameters for preparing CIGSS absorber layer using diethylselenide as selenium source. The Mo film was sputter deposited on 2.5 cm x 10 cm soda-lime glass using DC magnetron sputtering for studying the adhesion and chemical reactivity with selenium and sulfur containing gas at maximum film growth temperature. Mo being a refractory material develops stresses, nature of which depends on the deposition power and argon pressure. It was found that the deposition sequence with two tensile stressed layers deposited at 200W and 5 x 10-3 Torr argon pressure when sandwiched between three compressively stressed layers deposited at 300 W power and 0.3 x 10-3 Torr argon pressure had the best adhesion, limited reactivity and compact nature. An organo-metallic compound, diethylselenide (DESe) was developed as selenium precursor to prepare CIGSS absorber layers. Metallic precursors Cu-In-Ga layers were annealing in the conventional furnace in the temperature range of 475oC to 515 oC and in the presence of a dilute DESe atmosphere. The films were grown in an indium rich regime. Systematic approaches lead to the optimization of each step involved in the preparation of the absorber layer. Initial experiments were focused on obtaining the range of maximum temperatures required for the growth of the film. The following experiments included optimization of soaking time at maximum temperature, quantity of metallic precursor, and amount of sodium in terms of NaF layer thickness required for selenization. The absorber surface was coated with a 50 to 60 nm thick layer of CdS as hetero-junction partner by chemical bath deposition. A window bi-layer of i:ZnO/ZnO:Al was deposited by RF magnetron sputtering. The thickness of i:ZnO was increased to reduce the shunt resistance to improve open circuit voltage. The cells were completed by depositing a Cr/Ag front contact by thermal evaporation. Efficiencies greater than 13% was achieved on glass substrates. The performance of the cells was co-related with the material properties.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science and Engineering
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Domanski, Daniel Feliks Raphael. "The electrodeposition of metallic molybdenum thin-film coatings, from aqueous electrolytes containing molybdate ions." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/55131.
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Electrodeposition of metallic molybdenum from aqueous electrolyte has in most cases previously yielded poor results due to the extremely high rate of the secondary hydrogen evolution reaction occurring at the cathode. This results in low current efficiencies and thin brittle films. The use of a highly concentrated aqueous-acetate based electrolyte containing molybdate ions has been used to deposit thick (~50 μm) adhered, mirror like metallic molybdenum coatings. Plating variables were investigated to determine the optimum deposition conditions; it was seen that current density was the most influential factor for the successful deposition of the refractory metal. The coating surface was analysed using SEM and EDX. XRD analysis confirmed the deposits were amorphous in nature with broad peaks in the (110) orientation.
The deposition mechanisms were studied through electrochemical techniques such as PDP and CV. It was concluded that metallic molybdenum is deposited in a two-step reduction process, with the formation of an intermediate coating of molybdenum oxide, requiring hydrogen gas to fully reduce. Corrosion studies have shown the coatings stability in a chlorinated environment however active uniform corrosion in alkaline conditions resulted in film failure. Exposure to strong acidic conditions result in oxidation and delamination of the coating.
Up-scaling of the process was seen to be successful and large deposits of well adhered and uniform metallic molybdenum were formed under high applied currents.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
29
Li, Bohao. "Room Temperature Processed Molybdenum Oxide Thin Film as a Hole Extraction Layer for Polymer Photovoltaic Cells." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1368015443.
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Zhang, Panpan, Sheng Yang, Roberto Pineda-Gómez, Bergoi Ibarlucea, Ji Ma, Martin R. Lohe, Teuku Fawzul Akbar, Larysa Baraban, Gianaurelio Cuniberti, and Xinliang Feng. "Electrochemically Exfoliated High-Quality 2H-MoS₂ for Multiflake Thin Film Flexible Biosensors." Wiley-VCH, 2019. https://tud.qucosa.de/id/qucosa%3A73171.
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2D molybdenum disulfide (MoS₂) gives a new inspiration for the field of nanoelectronics, photovoltaics, and sensorics. However, the most common processing technology, e.g., liquid‐phase based scalable exfoliation used for device fabrication, leads to the number of shortcomings that impede their large area production and integration. Major challenges are associated with the small size and low concentration of MoS₂ flakes, as well as insufficient control over their physical properties, e.g., internal heterogeneity of the metallic and semiconducting phases. Here it is demonstrated that large semiconducting MoS₂ sheets (with dimensions up to 50 µm) can be obtained by a facile cathodic exfoliation approach in nonaqueous electrolyte. The synthetic process avoids surface oxidation thus preserving the MoS₂ sheets with intact crystalline structure. It is further demonstrated at the proof‐of‐concept level, a solution‐processed large area (60 × 60 µm) flexible Ebola biosensor, based on a MoS₂ thin film (6 µm thickness) fabricated via restacking of the multiple flakes on the polyimide substrate. The experimental results reveal a low detection limit (in femtomolar–picomolar range) of the fabricated sensor devices. The presented exfoliation method opens up new opportunities for fabrication of large arrays of multifunctional biomedical devices based on novel 2D materials.
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Hogan, Royston Hugh. "Scanning tunneling microscopy and photoelectron spectroscopy of thin film dichromium tetraacetate and dimolybdenum tetraacetate on single crystal graphite and molybdenum disulphide." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/184992.
Full textAbstract:
Scanning tunneling microscopy has been used to investigate the structural characteristics of thin film dimolybdenum tetracetate on single crystal graphite and molybdenum disulphide substrates. The results indicate that the observed surface structures of the films correspond to two-dimensional crystal faces of the three-dimensional X-ray crystal structure of dimolybdenum tetraacetate. The electronic structure of the films was investigated using photoelectron spectroscopy and correlated to the observed surface structures. Furthermore, thin films of dichromium tetraacetate as well as mixed films of the two dimers on graphite and molybdenum disulphide were also investigated by valence photoelectron spectroscopy.
32
Cano, Garcia Jose. "Damp Heat Degradation of CIGS Solar Modules." Thesis, Högskolan Dalarna, Energiteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:du-26006.
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Due to the short period that some photovoltaic technologies have taken part on the solar energy market, it is crucial to evaluate the long term stability of solar cells belonging to those technologies in order to ensure a minimum lifetime of their performance. Accelerated degradation tests are thus carried out to achieve such goals. The present study analyzes the encapsulation effects on co-evaporated manufactured Copper Indium Gallium Selenide (CIGS) solar cells under damp heat conditions, consisting in 85 °C and 85 % relative humidity, during an approximated period of 1000 hours. The experimental procedure has been carried out at Solliance Solar Research facilities. Since the encapsulation packages play a critical role as a protection to achieve long term stability of the solar cells and modules, several packaging structures and materials has been taken into study. Thus, eighteen types of mini modules were manufactured including different combinations of encapsulants, front sheet foils, thin film protective barriers and CIGS cells from different manufacturers. The design of these mini modules and the manufacturing process to obtain them is also presented in this work. Various characterization techniques were carried out in order to acquire the required information about the solar cells and encapsulants performance along the damp heat degradation process. The results exposed that encapsulation packages including thin film barriers between the encapsulant and the front sheet foil allowed a longer solar cell lifetime due to their remarkable protection against moisture ingress. Moreover, the degradation of the molybdenum layer included in the CIGS cells was found as principal cause of efficiency decrement and end of performance of solar cells protected by regular encapsulant and front sheet foils. Some other findings in relation with the evaluated components are shown along the present study.
33
Murphy, Neil Richard. "Reactive sputtering of mixed-valent oxides: a route to tailorable optical absorption." University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1427889137.
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Boujida, Mohamed. "Contribution à l'étude des propriétés de transport de quelques oxydes métalliques et supraconducteurs de basse dimensionnalité." Grenoble 1, 1988. http://www.theses.fr/1988GRE10157.
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Les proprietes de transport (magnetoconductivite, effet hall, ondes de densite de charge, ondes de densite de spin, transitions supraconductrices) des oxydes metalliques et supraconducteurs quasi-bidimensionnels sont etudiees a basse temperature
35
Lenoble, Marie-Anne. "Dépot électrolytique de CoFeCu, matériau magnétique doux de forte induction pour tetes magnétiques." Grenoble INPG, 1995. http://www.theses.fr/1995INPG0156.
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L'alliage cofecu a ete choisi pour son aptitude a repondre aux criteres que doit remplir tout nouveau materiau magnetique doux des tetes magnetiques. Une etude electrochimique des phenomenes de depot, a permis de preciser les parametres operatoires qui influent sur la composition de l'alliage. Des depots sont d'abord realises sur de grandes surfaces pour les caracterisations magnetiques et structurales: un lien est etabli entre la composition donnant les proprietes optimales et la structure de l'alliage. Les depots dans des caissons de taille micronique pour les tetes magnetiques couches minces sont ensuite etudies pour optimiser l'obtention de la piece polaire superieure. Le depot est enfin realise sur de vraies tetes qui sont ensuite testees. Les resultats obtenus sont encourageants car l'overwrite et le wiggle sont bien ameliores. La tenue en frequence pourrait etre amelioree en appliquant un champ magnetique plus eleve pendant le depot. Des ajouts de molybdene dans l'alliage ont conduit a de meilleures proprietes magnetiques laissant esperer une reponse encore meilleure de la tete
36
XIE, MING-XUN, and 謝銘勳. "Interfacial reactions of molybdenum thin films on silcon." Thesis, 1991. http://ndltd.ncl.edu.tw/handle/42920464917601212287.
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Chan, Yu-Hao, and 詹祐豪. "Chemical Vapor Deposition of Molybdenum Disulfide Thin Films." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/81968044488168669879.
Full textAbstract:
碩士國立臺灣大學
材料科學與工程學研究所
104
Molybdenum disulfide (MoS2) is a two-dimensional hexagonal lattice. In contrast to graphene, which has no bandgap by nature, MoS2 monolayer has a direct bandgap of 1.8 eV due to the quantum confinement effect. It exhibits a high on/off current ratio and strong luminescence. Therefore, MoS2 monolayers have attracted much attention in experimental and theoretical researches for its potential applications in optoelectronic devices, field effect transistors, low power switches, valleytronics, etc. For practical applications, it is of importance to develop a reliable growth process to synthesize large-area, uniform, and continuous MoS2 monolayers. Here we use the chemical vapor deposition method for the growth of MoS2 atomic layers, using the precursors, MoO3 and sulfur and high-purity argon carrier gas, onto the silicon oxide substrates. In this study, we investigate the influences of growth temperature, pressure, substrate positions and the substrate orientation on the morphology and thickness of the MoS¬2 thin films and infer the mechanism of MoS2 growth in our system from the experimental results. Continuous MoS2 bilayers in a size of 3.5×2.2 cm2 can be obtained. They exhibit an on/off ratio of 104, mobility of ~10 cm2/V-s, and high luminescence, which is ~13 times stronger than that of the exfoliated MoS2 monolayers.
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Srinivas, G. "Structural, optical and electrical properties of molybdenum silicide thin films." Thesis, 1993. http://localhost:8080/xmlui/handle/12345678/3103.
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Pradhan, Diana. "Rapid Thermal Synthesis of Molybdenum Disulfide Thin Films for Infrared Detectors." Thesis, 2021. http://ethesis.nitrkl.ac.in/10336/1/2021_PhD_DPradhan_516PH1012_Rapid.pdf.
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Automation and modernization of gadgets in automobiles, safety, remote sensing, defence, agriculture, environmental pollution, imaging in nuclear medicine rely on the use of infrared (IR) detectors. In the current era of IR detectors, the quest for advanced materials turned the research towards transition metal dichalcogenides. Molybdenum disulfide (MoS2) is found to be a suitable candidate for IR detectors as it outperforms over a broad range of IR spectrum. In order to obtain a superior quality of MoS2 films, chemical vapor deposition has been explored which involves sulfurization of various Mo based compounds using inert carrier gases over a prolonged period of time at high process temperature. In this research, a short period growth of MoS2 films is implemented by face to face arrangement of pre-deposited S/Mo films on silicon substrates using rapid thermal process (RTP). In this work, an attempt has been made to explore the dependence of the RTP parameters such as growth duration, process time and gas flow rate on the morphological, microstructural and electronic properties of MoS2 thin films. Morphological properties of RTP grown MoS2 thin films have been investigated by Field Emission Scanning Electron Microscope and Atomic Force Microscope technique, whereas microstructural properties have been studied by X-Ray Diffraction and Raman technique. The electronic properties of the MoS2 films are estimated by current-voltage and capacitance-voltage technique. A correlation between the morphological and electronic properties of RTP grown MoS2 thin film has been systematically established in this research. The MoS2 films with improved morphological and electronic properties have been obtained at 800 °C for the growth duration of 5 min with the Ar:H2 flow rate of 10:1. The n-type and p-type MoS2 thin films are fabricated using benzyl viologen (BV) and gold chloride (AuCl3) solution, respectively by spin coating technique. The modulation of morphological and electronic properties of MoS2/Si samples was studied with the variation in concentration of BV and AuCl3 solution, number of spin coats and temperature of post-treatment annealing. The MoS2 based photoconductive detector, heterojunction, homojunction and Schottky junction are fabricated to investigate IR detection behavior at the wavelength of 850 nm, 940 nm and 1060 nm. MoS2 based Schottky junction has shown a higher current On/Off ratio, whereas fast rise and fall time has been observed for photoconductive devices. MoS2 thin films, synthesized by RTP have shown comparatively better IR detection behavior for 940 nm IR illumination. The above observations will pave a suitable platform for the next generation of IR detectors.
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Yang, Shih-Yih, and 楊士逸. "Chemical Vapor Deposition of Thin Films from Bisimido Molybdenum Complex and Alane Complex." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/13846862653662059087.
Full textAbstract:
碩士國立交通大學
應用化學系
82
The imido complex Mo(NtBu)2(NEt2)2 and alaneound AlH3(NMe2Et)n (n=1 or2) were successfully synthesized. Mo(NtBu)2(NEt2)2 was prepared by the reaction of Mo(NtBu)2Cl2DME with LiNEt2. AlH3( NMe2Et)n (n=1 or2) wasthesized by reacting LiAlH4 with 1eq. of Me2EtN.HCl andMo(NtBu)2(NEt2)2 and AlH3(NMe2Et)n (n=1 or2) were used as precusor to depo-sit thin films on silicon substrates in a cold-wall CVD reactor at 0.03-0.1 Torr,723-923K and 363-503K,respectively. The thin films were characterized by SEM, XRD,WDS and ESCA. For this films deposited from Mo(NtBu)2( NEt2)2, SEM and XRD indicated that the films were poly- crystalline. WDS studies show that the conctitution of the films were MoCxNyOz, x=0.06-0.63, y=0.49-0.76, z=0.02-0.34, with increasing deposition temperature, the carbon and nitrogen centration decreased. XRD studies found that when the temperature deposition has increased, the films show sharp and shift diffraction peaks. Compare with the WDS data, with increasing N/Mo, C/Mo ratio,the lattice parameter increased. Volatile products were analyzed by RGA. From the analysis, decomposition of the tBuN and Et2N groups by β-hydrogen elimination and methyl elimination pathways are proposed. For Al thin films deposited from AlH3(NMe2Et)n (n=1 or2), SEM indicated that they were grown selectively on Si, TiN and TiSi2 in the presence of SiO2. The average grain size for Al on Si is approximately 500A, ten times smaller than found on TiN(5000 A), indicating that Al nuclei are much easily formed on TiN than SiO2. Conformal deposition can be easily achieved for filling unity aspect ratio holes. XRD studies found very sharp diffraction peaks. The resistivity for Al films are 3.1 uohm- cm, which is 10-20% higher than the 2.7 uohm-cm bulk resistivity. We also explore the films deposited from Mo( NtBu)2(NEt2)2 which covered Al thin films deposited from AlH3( NMe2Et)n (n=1or2) as diffusion barrier.
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Liu, Hong-Shan, and 劉轟山. "Characterization of Gallium Nitride Thin Films Grown on Chemical-Vapor-Deposited Molybdenum Disulfide." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/63m75f.
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碩士國立東華大學
材料科學與工程學系
107
In this study, we used chemical vapor deposition (CVD) to grow a large area MoS2 on 2-inch sapphire as substrate, and then GaN thin film were grown on MoS2/sapphire by plasma-assisted molecular beam epitaxy (PA-MBE). We try to investigate effects of deposition parameters on the properties of GaN films, in order to have a large area and high quality GaN/MoS2 heterostructure thin film. To understand the influence of different pre-nitrogen temperature, different growth time, different Ga-temperature (nitrogen first) and different Ga-temperature (gallium first). During the growth, the Reflection High Energy Electron Diffraction (RHEED) can help us to monitor the surface condition of samples. Field Emission Scanning Electron Microscope (FE-SEM), Raman spectroscope, Photoluminescence spectroscope (PL) and High Resolution X-ray Diffraction (HRXRD) were applied to analyze the morphology, structure and quality of GaN thin films. In summary, we deposited GaN thin film on CVD MoS2/sapphire substrate successfully. In consequence, lower pre-nitrogen temperature can protect the MoS2 two-dimension structure more effectively, extend the time of growth and increase the temperature of gallium cell will enhance optical properties and make the grain morphology become hexagonal crystal. But the result of gallium first is worse than nitrogen first.
42
Tsao, Chin-Wei, and 曹晉瑋. "Growth and Microstructure Analysis of Molybdenum Disulfide Thin Films by Chemical Vapor Deposition." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/xzr84g.
Full textAbstract:
碩士國立臺灣大學
材料科學與工程學研究所
107
Molybdenum disulfide is one of the 2D materials which has been widely studied. Similar to graphene, its lattice is hexagonal. The most interesting property of molybdenum disulfide is when the layer thickness is reduced from bulk to single layer, its bandgap will change from an indirect bandgap of 1.0 eV to a direct bandgap of 1.8 eV. This makes single layer of molybdenum disulfide expected to be a material for various electronic or optical devices. There are many methods to get single layer molybdenum disulfide, especially chemical vapor deposition(CVD) is an extensive method to synthesize large-area single layer molybdenum disulfide. In our experiments, we tuned parameters such as growth temperature, carrier gas flow, placement of substrate, addition of sodium chloride to investigate and analyze influences. In order to measure property of single grain molybdenum disulfide, we adjusted parameters to increase grain size from 200 nanometers to 30 microns. It was found that there are many tiny second layers of molybdenum disulfide grains on the first layer grains grown at high temperatures. We assume that this results in many active sites for hydrogen evolution reaction in the unit area of the grain, which makes hydrogen evolution reaction (HER) efficiency better than perfect single-layer molybdenum disulfide grain.
43
Liao, Hung-Pin, and 廖宏彬. "Study on Optoelectrical Properties and Surface Texturing of Molybdenum Doped Zinc Oxide Thin Films." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/14344555213701219216.
Full textAbstract:
碩士南台科技大學
光電工程系
96
Zinc oxide (ZnO) thin films with a strong c-axis preferred orientation, obvious piezoelectric and piezo-optical effects, have been used in acoustoelectric and acousto-optical devices. Besides, the surface textured or “cratered” morphology of ZnO films have a potential application in enhanced light trapping in optical devices such as solar cells. The conduction characteristics of ZnO film with typical resistivity of 1-100 Ω-cm. These primarily dominated by electrons due to the oxygen vacancies and Zn interstitial atoms. In order to improve electric conductivity of the ZnO n-type semiconductor, the proper metal of choosing to enhanced carrier concentration is a feasible and effective method. In this research, we prepared Mo doped ZnO thin films on glass a substrate using co-sputtering to improve the conductivity of ZnO. The incorporated concentration of Mo atoms in ZnO was controlled by adjusting the aperture size of a shutter palaced in front of the Mo target. Textured morphology of ZnO film could be formed by attaching a metallic mask on the substrate. The optoelectric properties and structure of Mo doped ZnO films dependent on process conditions are investigated. Results show that ZnO film doped with 1.84wt% Mo exhibits the highest concentration and conductivity and the lowest surface roughness. A resistivity of 7.52×10-3Ω-cm can be achieved after an annealing process of the MZO film. This is due to that the crystalline intensity and grain size of MZO film were increased after annealing, leading to reduced lattice scattering and impurity scattering effects. The optical transmittance of the MZO film were also improved by 1~2 %. Surface textures with a thickness of 100nm a diameter of 70μm were formed by attaching a metallic shadow mask to the subst rate. The surface textures could adjust optical path of an in coming light resulting in an optical transmittances reduction of 5%. This indicates the surface textured MZO films could enhance light diffusion efficiency. We also observed that the optical transmittance of MZO films decreases as the incident angle of light increases. Increase of thickness would enhance this angle effect to the optical transmittance. So that at high angle of incident the light diffusion refractive effect is more prominent.
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"Synthesis and characterization of diamond-like carbon and DLC-MoS2 composite thin films." Thesis, 2014. http://hdl.handle.net/10388/ETD-2014-12-1877.
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In order to obtain diamond-like carbon (DLC) thin films with improved mechanical, tribological, thermal and corrosion properties for practical applications, the structure and properties of various DLC thin films including hydrogen-free DLC, hydrogenated DLC, and DLC-MoS2 composites synthesized under different conditions were investigated in this thesis. The research methodologies and the main results are summarized in following paragraphs.
Hydrogen-free DLC thin films were synthesized by biased target ion beam deposition (BTIBD) method, while hydrogenated DLC thin films were deposited by ion beam deposition technique using a Kaufman-type ion source and an end-Hall ion source. DLC-MoS2 composite thin films were also synthesized using BTIBD technique in which MoS2 was produced by sputtering a MoS2 target while DLC was simultaneously deposited by ion beam deposition. The influence of processing parameters on the bonding structure, morphology and properties of the deposited films was investigated using atomic force microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, synchrotron based near edge X-ray absorption fine structure spectroscopy, X-ray diffraction, scanning electron microscopy, nanoindentation, ball-on-disk and corrosion testing. Finally, the influence of annealing temperature on the structure and properties of pure DLC and DLC-MoS2 composite films in ambient air and low pressure environments was studied.
In the case of BTIBD method, hydrogen-free DLC thin films with exceptionally high smoothness and low friction coefficient were prepared by biased target sputtering of graphite target without additional ion bombardment either by negative bias of substrate or assisting ion source. For ion beam deposition technique with Kaufman ion source, the DLC thin films synthesized at ion energies of 300 eV showed the highest sp3 content and optimum properties. Regarding end-Hall ion source, the best properties achieved in DLC films synthesized at ion energies of 100 eV.
Comparing with pure DLC and pure MoS2 films, the DLC-MoS2 films deposited at low biasing voltages showed better tribological properties including lower coefficient of friction and wear coefficient in ambient air environment. Also, comparing with pure DLC films, the DLC-MoS2 thin films showed a slower rate of graphitization and higher structure stability throughout the range of annealing temperatures, indicating a relatively higher thermal stability.
45
CHANG and WEN-HSIN. "Development of In-atmosphere Fabrication Methods for Crystalline Molybdenum Trioxide Thin Films and Their Characterizations." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/30587410869974276209.
Full textAbstract:
碩士國立中央大學
能源工程研究所
105
This study aims at developing in-atmosphere methods for fabricating molybdenum trioxide (MoO3) thin films. The microstructures of the crystallized thin films by different heat treatment schemes were examined and the effects of various heat treatment approaches on crystallization mechanisms were studied. The fabricated molybdenum trioxide films were finally used as the hole injection layer (HIL) for an hole only device (HOD) to verify their effects on hole injection gain. The effects of film thickness and crystallinity on the characteristics of the device were investigated. In this study, we also propose to prepare the solution through incorporating AHM with nitric acid (HNO3) as the precursor solution. In result, we successfully fabricate h-MoO3 crystalline thin films by the spin coating scheme. In the first part of this study, the precursor solution was deposited on an ITO substrate by the spin-coating technique. The samples were heat treated on a hot plate by different heat treatment conditions. To confirm that h-MoO3 thin film was successfully fabricated, the samples were then characterized by various analyses, including elementary, morphology analysis, crystalline and optical properties. The overall transmittance for MoO3 thin films on ITO ranges from 77 to 82% at the visible light spectrum (300 to 800 nm). When used in HOD, the degree of crystallinity of MoO3 thin film can be enhanced with the increase of film thickness that, compared with the conventional hole injection layer by PEDOT:PSS, shows favorable device performance. The second part of this thesis focuses on an alternative tool of heat treatment, CO2 laser. Since the wavelength of CO2 laser light is far infrared that provides excellent thermal effect on material processing. It is expected the crystalline of MoO3 thin films can be efficiently improved. Depending on laser powers and stage scan speeds, we observed, based on SEM images, MoO3 thin films were with various microstructures, such as needle-like, flake-like and block-like. We examine their properties and discuss their formation mechanisms.
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Weber, Frank John. "Changes in structure and stress in Mo/a-Si thin films upon annealing." Thesis, 1995. http://hdl.handle.net/1957/34701.
Full textAbstract:
The structural and stress changes in molybdenum/amorphous silicon (Mo/a-Si)
EUV reflecting multilayers during annealing at 316��C were studied. The amorphous
interlayers, with an Mo:Si stoichiometry of 1:2, grew during annealing. The residual
stresses in each component of the multilayer also changed significantly. Through high
resolution electron microscopy, selected area electron diffraction, and x-ray diffraction of
the crystalline Mo, the biaxial tensile stresses were shown to increase from approximately
two to about ten GPa in the lateral direction, parallel to the interface plane. The
compressive strains developed in the vertical direction, perpendicular the interface plane,
are consistent with a Poisson contraction calculated from bulk elastic properties. Laser
deflectometry measurements of thicker (non-EUV, 0.1��m) amorphous silicon showed
compressive stress relaxation in the amorphous silicon with annealing, which may also take
place in the thin (EUV) silicon. The residual stress in a 40 bilayer EUV film changes from
about -0.5 GPa to about +1.5 GPa.Graduation date: 1996
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Rao, L. LRajeswara. "Design, Fabrication and Characterization of Metal Oxide Semiconductor Based MEMS Gas Sensors for Carbon Monoxide Detection." Thesis, 2017. https://etd.iisc.ac.in/handle/2005/4788.
Full textAbstract:
In recent years, intense efforts have been made towards the development of miniaturized gas-sensing devices for hazardous gas detection. Carbon monoxide, which is a result of incomplete combustion, is a colourless, odourless, poisonous, explosive and highly toxic gas. It binds with haemoglobin to form carboxyhemoglobin, which reduces the oxygen-carrying capacity of blood and, finally, leads to death. Hence, there is a need to develop a portable and cost-effective gas senor to detect low concentrations of CO gas. MEMS-based metal oxide semiconductor gas sensors offer several advantages compared to conventional optical and electrochemical techniques, such as compact size, low power consumption, quick response, high-temperature stability and low cost for mass production. However, a high-temperature is required for the optimum performance of metal oxide semiconducting gas sensors and such temperatures can be achieved with microheaters.
The present thesis work deals with the design, fabrication and characterization of a MEMS gas sensor for the detection of low concentrations of carbon monoxide gas. The work is focused on five specific objectives: a) growth and characterization of sensing film; b) sensitivity enhancement using noble metal additives and nanowire structures; c) design, fabrication and characterization of microheaters; d) development of microhotplate integrated MEMS gas sensor; e) gas sensor packaging. The investigations undertaken are as follows:
Titanium dioxide thin film sensing material is deposited using DC magnetron sputtering. The deposition conditions are optimized to obtain stoichiometric TiO2 thin films and are characterized for carbon monoxide gas detection. The influence of the operating temperature, annealing temperature, thin film thickness and the interdigitated electrode geometry on the sensor response is investigated. The TiO2 thin film sensor (annealed at 800 °C) shows a high response (79.5 %) to CO gas and a low response (<23%) to other reducing and oxidizing gases at 400 °C. It is observed that the sorption is completely reversible and the response and recovery times are of the order of 50 and 120 sec respectively.
Noble metal additives such as Au, Pt, and Pd are decorated on the TiO2 surface to enhance the sensitivity and selectivity of the TiO2 thin film gas sensors. The pristine TiO2 thin film gas sensor (annealed at 400 °C) is found to exhibit a detectable response only when the operating temperature is above 300 °C; below this temperature there is no detectable change in resistance in the presence of 5000 ppb of CO gas. The response is found to increase with the operating temperature and it exhibits a maximum response of 58.6 % at 400 °C. The surface-modified TiO2 thin film based gas sensor shows a remarkable response event at 100 °C. The Au-TiO2 and Pt-TiO2 thin film gas sensor has been found to exhibit a maximum response of 83.46 and 79.64 % at 200 and 250 °C respectively, whereas, the Pd-TiO2 thin film gas sensor exhibits a n to p transition above 150 °C.
TiO2 nanowires are synthesized using hydrothermal processes and are characterized for the detection of low concentrations of carbon monoxide gas. The TiO2 nanowire-based gas sensor shows a detectable change in its resistance even at 150 °C and its response is found to increase with the temperature. At 400 °C, the sensor is found to exhibit a maximum response of 80 % for 5000 ppb of CO. Further, under the same operating conditions, the sensor is found to exhibit a remarkable change in its resistance (a response of 5.6 %) for 100 ppb of CO. The response and recovery times of the sensor are of the order of 18 and 27 s respectively.
Microheaters are designed and simulated using the CoventorWare MEMS design and analysis tool to optimize the geometry of the microheater structure for uniform temperature distribution and low power consumption. Low resistive molybdenum thin films are deposited for high temperature microheater applications. The molybdenum microheaters are fabricated and their electro-thermo-mechanical characteristics are studied. The microheater membrane stability is analyzed by measuring its deformation under high thermal stresses using an optical profilometer. The microheater response is characterized in both pulsed and constant temperature modes of operation; it is found to exhibit a negligible resistance drift after 600 hours of continuous operation, indicating its long-term thermal and mechanical stability. The response and recovery times are in the order of a few milliseconds (19 and 34 ms), which make them suitable for gas-sensing applications.
Finally, microhotplate integrated MEMS gas sensors are fabricated, packaged and characterized for carbon monoxide gas detection at elevated temperatures (250 to 700 °C). The sensitivity, selectivity, repeatability and response and recovery times of the miniaturized MEMS gas sensors are investigated. The developed MEMS gas sensor is found to exhibit a high sensitivity and selectivity to CO gas compared to the TiO2 thin film based gas sensor. It shows a highest response of 96.14 % for 5000 ppb of CO and a minimum response (< 28%) to other reducing and oxidizing gases at 550 °C optimized temperatures. The MEMS gas sensor is found to exhibit quick response and recovery times (9 and 21 s) compared to thin film-based gas sensors (50 and 120 s).
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Guimond, Sebastien [Verfasser]. "Vanadium and molybdenum oxide thin films on Au(111): growth and surface characterization / von Sebastien Guimond." 2009. http://d-nb.info/999461737/34.
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Tsai, Tsung-Hsien, and 蔡宗憲. "A Study on Deposition of Flexible Electrochromic Tungsten-Molybdenum Oxides Thin Films by Atmospheric Pressure Plasmas." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/98864246214731016395.
Full textAbstract:
碩士逢甲大學
化學工程學所
98
Electrochromic material is expanding quickly in recent years as a result of the global energy shortage. Electrochromic devices(ECDs) contain low drive voltage, shorter response time, and the devices exhibit an open-circuit memory. They can independently control indoor lighting and shade, and usually have application to energy-conserving windows, effectively reaching the goal of saving energy for indoor air conditioning and illumination use. In accordance with market trends, the flexible electrochromic device is more obvious day by day, because of its advantages of the lightweight, flexibility and mass production (can use reels of roll to roll production), and they hold broad-spectrum potential for future development. This study uses the atmospheric pressure plasma polymerization method to utilize monomer W(CO)6 and Mo(CO)6 preparation of flexible electrochromic film for tungsten-molybdenum oxide deposited on PET/ITO (Polyethyleneterephthate/Indium Tin Oxide) plastic substrate. Because the advantages of this process are fast and low cost, vacuum equipment and vacuum chambers are not required. Therefore without the need of vacuum chambers, there are no limitations to the size of the substrate dictated by vacuum chambers. This increases the fast thin film coating speed. So this conforms to the industrial requirements to be able to meet mass production conditions. The advantages of tungsten oxide and molybdenum oxide are its good contrast of transmittance, its optical properties, its stability, and its promotion of the electrochromic properties of tungsten oxide and molybdenum oxide by mixing the aforementioned two monomers. This study discusses the preparation of flexible electrochromic devices, PET/ITO/WxMo1-xO3, produced by the atmospheric pressure plasma, and probes into the electrochemical properties, optical properties and electrochromic properties by utilizing three methods: the cyclic-voltamogram method, the step method and the UV-VIS spectroscopy method. A Field Emission Scanning Electron Microscope was used to analyze the film thickness and its surface morphology. Moreover, Electron Spectroscopy for Chemical Analysis was applied to the analysis of the chemical configuration in the WxMo1-xO3 thin film. The results of this study prove the successful coating of a fine electrochromic property of tungsten-molybdenum oxide thin film on the PET/ITO plastic substrate by the atmospheric pressure plasma process. The transmittance change can reach to 76% under a wavelength of 550nm, and after 200 cycles of testing by the cyclic-voltamogram method, the WxMo1-xO3 thin film still had good stability.
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Yoder, Karl Bruce. "Deformation and strengthening mechanisms in PVD molybdenum thin films based on an activation analysis of nanoindentation hardness data." 1997. http://catalog.hathitrust.org/api/volumes/oclc/38427210.html.
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