Dissertations / Theses on the topic 'Oxygen vacancy'
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Kullgren, Jolla. "Oxygen Vacancy Chemistry in Ceria." Doctoral thesis, Uppsala universitet, Strukturkemi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-167521.
Full textChen, Haiyan. "Probing Defects and Electronic Processes on Gadolinia-doped Ceria Surfaces Using Electron Stimulated Desorption." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10427.
Full textWang, Xiaoshuang. "Multiscale modeling of oxygen and vacancy diffusion in dilute ferritic iron alloys." Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A72722.
Full textWang, Xiaoshuang [Verfasser], Jürgen [Gutachter] Faßbender, and Karsten [Gutachter] Albe. "Multiscale modeling of oxygen and vacancy diffusion in dilute ferritic iron alloys / Xiaoshuang Wang ; Gutachter: Jürgen Faßbender, Karsten Albe." Dresden : Technische Universität Dresden, 2020. http://d-nb.info/1227311273/34.
Full textLin, Hong-Ying. "Improving the optoelectronic property and photoactivity of nano-structured titanuim dioxide effect of particle size, oxygen vacancy, and nitrogen doping /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 1581 p, 2008. http://proquest.umi.com/pqdweb?did=1609302401&sid=2&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full textPrincipal faculty advisors: Chin-Pao Huang, Dept. of Civil and Environmental Engineering, and S. Ismat Shah, Dept. of Materials Science Includes bibliographical references.
Girdauskaite, Egle. "Thermodynamische und kinetische Untersuchungen zum Sauerstoffaustausch in perowskitischen Mischoxiden auf Basis von Ferriten und Cobaltiten." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1195658113234-25483.
Full textIwata, Tatsuya. "Study on Resistive Switching Phenomenon in Metal Oxides for Nonvolatile Memory." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188598.
Full textPeng, Yung-Kang. "Surface mapping of faceted metal oxides by chemical probe-assisted NMR for catalytic applications." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:7b56021f-71fb-437b-8c6b-0569705ef68e.
Full textNishi, Yusuke. "Nonpolar Resistive Switching Based on Quantized Conductance in Transition Metal Oxides." Kyoto University, 2019. http://hdl.handle.net/2433/242544.
Full textUmeda, Yuji. "Rational design of dielectric oxide materials through first-principles calculations and machine-learning technique." Doctoral thesis, Kyoto University, 2020. http://hdl.handle.net/2433/245844.
Full text0048
新制・課程博士
博士(工学)
甲第22159号
工博第4663号
新制||工||1727(附属図書館)
京都大学大学院工学研究科材料工学専攻
(主査)教授 田中 功, 教授 中村 裕之, 教授 邑瀬 邦明
学位規則第4条第1項該当
Doctor of Philosophy (Engineering)
Kyoto University
DFAM
Shojaee, Kambiz. "Fundamental aspects of ammonia oxidation on cobalt oxide catalysts." Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/13657.
Full textLortie, Maxime. "Reverse Water Gas Shift Reaction over Supported Cu-Ni Nanoparticle Catalysts." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31733.
Full textSaines, Paul James. "Structural Studies of Lanthanide Double Perovskites." Thesis, The University of Sydney, 2008. http://hdl.handle.net/2123/3939.
Full textSaines, Paul James. "Structural Studies of Lanthanide Double Perovskites." Faculty of Science. School of Chemistry, 2008. http://hdl.handle.net/2123/3939.
Full textThis project focuses on the examination of the structures of lanthanide containing double perovskites of the type Ba2LnB'O6-d (Ln = lanthanide or Y3+ and B' = Nb5+, Ta5+, Sb5+ and/or Sn4+) using synchrotron X-ray and neutron powder diffraction. The first part of this project examined the relative stability of R3 rhombohedral and I4/m tetragonal structures as the intermediate phase adopted by the series Ba2LnB'O6 (Ln = lanthanide (III) or Y3+ and B' = Nb5+, Ta5+ or Sb5+). It was found that I4/m tetragonal symmetry was favoured when B' was a transition metal with a small number of d electrons, such as Nb5+ or Ta5+. This is due to the presence of p-bonding in these compounds. In the Ba2LnNbO6 and Ba2LnTaO6 series R3 rhombohedral symmetry was, however, favoured over I4/m tetragonal symmetry when Ln = La3+ or Pr3+ due to the larger ionic radius of these cations. The incompatibility of the d0 and d10 B'-site cations in this family of compounds was indicated by significant regions of phase segregation in the two series Ba2Eu1-xPrxNb1-xSbxO6 and Ba2NdNb1-xSbxO6. In the second part of this project the compounds in the series Ba2LnSnxB'1-xO6-d (Ln = Pr, Nd or Tb and B' = Nb5+ or Sb5+) were examined to understand the relative stability of oxygen vacancies in these materials compared to the oxidation of the lanthanide cations and to determine if any oxygen vacancy ordering occurred. It was found, using a combination of structural characterisation, X ray Absorption Near Edge Structure and Ultra-Violet, Visible and Near Infrared spectroscopies, that with Ln = Pr or Tb increased Sn4+ doping results in a change in the oxidation state of the Ln3+ cations to Ln4+. This leads to those series containing little or no oxygen vacancies. A loss of B site cation ordering was found to accompany this oxidation state change and phase segregation was found to occur in the Ba2PrSnxSb1-xO6-d series most likely due to the Pr3+ and Pr4+ cations segregating into different phases. The Nd3+ cations in the series Ba2NdSnxSb1-xO6-d, however, can not oxidise to the tetravalent state so the number of oxygen vacancies rises with increasing x. It was found that oxygen vacancies concentrate onto the axial site of the compounds with x = 0.6 and 0.8 at ambient temperature. In Ba2Sn0.6Sb0.4O5.7 the oxygen vacancies were found to change to concentrating on the equatorial site at higher temperatures and it is suggested that this oxygen vacancy ordering plays a role in the adoption of I2/m monoclinic symmetry.
Kang, Yuhong. "Mechanisms, Conditions and Applications of Filament Formation and Rupture in Resistive Memories." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/77593.
Full textPh. D.
Chen, Junbo. "Effect of Defects and Photoexcited Electrons on CO2 Reduction using Supported Single Atom Catalysts." Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-theses/1266.
Full textAli, Fawad. "Investigation of metal oxides thin films developed by PVD system for perovskite solar cells." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/127139/1/Fawad_Ali_Thesis.pdf.
Full textAsplet, William. "Etude des interactions entre les défauts lacunaires et les solutés Y,O, Ti pour mieux comprendre leur rôle dans la formation des nanoparticules d'oxydes dans les aciers ODS." Thesis, Orléans, 2018. http://www.theses.fr/2018ORLE2056/document.
Full textThis PhD thesis is dedicated to the study of interaction between vacancies and Y, Ti,O solutes for a better understanding of formation of oxide nanoparticles in ODS steel (Oxide Dispersion Strengthened). These ODS steels are considered as structural material for the next generation of fission and fusion nuclear reactors. Their good properties are induced by the fine dispersion of low size oxide nanoparticles. However, obtaining this distribution is not mastered and atomic scale clustering is not yet defined. Furthermore, it was shown by theoretical models that the presence of vacancy during mechanical alloying could affect the formation of these nanoparticles. This study follows upon on a previous study made by C.He, and bring new results, new interpretation and conclusions. Some implantations with Y, Ti, O ions with several energy have been made in order to simulate the mechanical alloying step used for ODS steel fabrication. Theses irradiations have induced defects and solutes into the iron matrix. Then we characterized samples using positron annihilation spectroscopy (PAS) and secondary ion mass spectrometry (SIMS). The nature of defects was studied according to nature of the implanted ion and the annealing temperature by PAS and correlated to depth profiles of solutes obtained by SIMS. Annihilation characteristics of some defects still unknown were able to be determined thanks to positron lifetime measurements. SIMS analysis showed that titanium doesn’t migrate for annealing experiments between 100°C and 450°C and that oxygen show a complex behavior of migration and trapping dependent on the microstructure of the material. PAS results show that ionic implantations produce vacancy clusters, dislocations and solutes-vacancies complex. Their proportion changes as a function of depth and nature of these irradiations. Vacancy clusters and dislocations are detected deeper than the implantation peak with a higher fraction for the dislocations indicating that the defects were able to migrate during implantations. The fraction of vacancy-solutes complexes is the highest in the ion stopping zone and is in a good agreement with the theoretical binding energy of vacancies-solutes complex. The nature and the distribution of the defects evolve according to the annealing temperature. Vacancy clusters disappear between RT and 300°C while the dislocations are eliminated from 400°C. Oxide phases are detected for annealing at 500 and 550°C in relation with the oxygen contamination during these annealings. Some defects which the nature is not yet identified were highlighted for annealing between 300 and 400°C for Y, O and Y+O irradiations
Saadi, Lama. "Etude de l'adsorption des molécules simples sur WO3 : application à la détection des gaz." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4346/document.
Full textThe team of micro sensors at IM2NP mainly focuses onthe development of gas sensors based on measurement in conductancevariation in presence of gas. The material used as sensitive element istungsten oxide (WO3) thin film. The objective of present thesis is to studythe surface properties of WO3 in its reconstruction c(2x2), obtained bycleavage along the [001] direction. This study is also followed by a gapanalysis using ab initio calculations based on DFT in both LDA andGGA approximations. Then, the adsorption of molecules of simple gases((O3, COx NOx) for these surfaces (more or less rich in oxygen), is performed.To simulate these systems, we have chosen the SIESTA code based onDFT which is used for the larger number of atoms as compared to other codes
Er-Rakho, Lahcen. "Oxydes de cuivre a valence mixte : perovskites deficitaires en oxygene." Caen, 1987. http://www.theses.fr/1987CAEN2036.
Full textGuttman, Jeremy. "Polymer-based Tunnel Diodes Fabricated using Ultra-thin, ALD Deposited, Interfacial Films." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469125487.
Full textVitoux, Laura. "Etude électrochimique et structurale du système NaxMoO2." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0362/document.
Full textThis work concerns the investigation of the phase diagram of sodium layered oxides NaxMoO2in the search of new materials. Structural transitions upon sodium electrochemical(de)intercalation were studied by electrochemistry combined with in situ X-ray diffraction forcompositions ½ ≤ x ≤ 1 et ¼ < x ≤ ½. It was shown that the very undulating aspect of theelectrochemical curve results from multiple structural rerarrangements upon cycling. Especiallynumerous NaxMoO2 specific phases have been evidenced, for which sodium/vacancy orderingsas well as the formation of Mo-Mo bonds are expected. Na~1/2MoO2, Na~2/3MoO2 et NaMoO2compounds have been (electro)chemically synthesized and their structural characterizationreveals complex structures, such as chains of diamond-like molybdenum clusters in NaMoO2
Huang, Mei-tzu, and 黃眉滋. "Oxygen vacancy dependent magnetism in CeO2 nanoparticles." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/gtgfy7.
Full text國立臺灣科技大學
工程技術研究所
99
This study investigated the magnetism of CeO2 nanoparticles prepared by thermal decomposition method. At first, it is found that the properties of CeO2 NPs were strongly related to the synthesis parameters. CeO2 NPs prepared by using Octyl ether as solvent have higher degree of oxygen deficiency than that of NPs using Benzyl ether a solvent. The concentration of Ce3+ is 42% of the former and 18% of the latter. Importantly, the former one is paramagnetic while the later one is ferromagnetic at room temperature. Then the CeO2 NPs were undergo different redox treatments. It includes the annealing in different oxygen partial pressure at 500℃ for 2hrs, and the annealing in air at 500℃ for different time. Combined the XAS and TEM analysis, it was found that the oxygen vacancy tends to locate at the surface of NPs. In addition, it was found that the magnetism of CeO2 NPs is related to the concentration of Ce3+ at surface. According to our results, it is proposed that the highest Ms will be obtained in CeO2 NPs with 35%~40% Ce3+ at surface.
Lin, Yu-shiang, and 林裕翔. "The oxygen vacancy and spin polarization of cuprous oxide nanoparticle." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/50981798243992667228.
Full text國立中央大學
物理研究所
95
In studying the magnetic properties of cuprous oxide nanoparticle. We got a group of M-H curve measurements of cuprous oxide nanoparticle and discovered hysteresis at 1.8 K and 5 K. Then we pressed the cuprous oxide sample to control the interparticle separation, and dicussed the effect of interparticle interaction. The range of compacting density (CD) of particles is from 3 % to 77 % . There are two magnetic components in cuprous oxide nanoparticle system. We infer that one component is surface spin polarization and the other is magnetic characters of Cu2O0.9nanoparticle. The saturated magnetization (Ms) of spin polarization increases as the interparticle separation is decreased. The behavior can be taken the form of magnetic dipole-dipole interaction. After pressing the sample,we never discovered hysteresis again and diamagnetic properties was revealed.
Yu, Szu Chun, and 尤思淳. "Threshold Voltage Tuning and Oxygen Vacancy Passivation for Advanced FinFET." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/35ms4m.
Full text國立清華大學
工程與系統科學系
103
FinFET devices have higher on current and lower leakage current due to better gate control ability compared to the conventional single gate planar FETs. With the scaling of gate length, threshold voltage tuning by channel doping will be an issue. With the scaling of EOT, flat band voltage roll-off caused by oxygen vacancy needs to be solved. There are three parts in this thesis to dicuss the impacts of high-k/metal gate process on device characteristics, which are plasma nitridation, ALD pulse time and ALD growth temperature modulation. In the first part, different time of plasma assisted nitridation is implemented on metal gate to adjust work function and achieve multi-Vt FinFET. It has been reported that threshold voltage in PFinFET decreases with a higher nitrogen concentration in metal gate. However, results in this work are contrary to expectation. It supposes that nitrogen concentration of metal gate is already saturated, and effective work function may be decreased with further nitridation treatment. The on current is increased over 5-6% for PFinFET and slightly decreased for NFinFET, which are consistent with the results of EOT. Two possible mechanisms are proposed to explain electrical characteristics of FINFET, which are nitrogen diffusion into high-k layer and interfacial layer regrowth. In the second part, two different H2O pulse time in ALD are implemented to study the oxygen vacancy effect. The crystallization of high-k is transferred into monoclinic phase with higher oxygen content by a longer H2O pulse time. Less oxygen vacancy can be also obtained, which is verified by the increased and decreased threshold voltage for NFinFET and PFinFET, respectively. Sub-threshold swing, Dit, and leakage current are decreased, and good reliability is obtained by longer H2O pulse time in ALD although EOT is slightly increased. In the third part, two different deposition temperatures in ALD are implemented to study the oxygen vacancy effect. The crystallization phase of high-k is transferred to more stable monoclinic by a higher deposition temperature in ALD. Smaller standard deviation of threshold voltage can be achieved by a higher deposition temperature in ALD because of the reduced oxygen vacancy. EOT is slightly increased due to the higher oxygen content in high-k, and it doesn’t decrease the on current. Sub-threshold swing, Dit, and leakage current are decreased, and good reliability is obtained as well.
Karapetrova, Euguenia. "Factors influencing the crystallization, phase and oxygen vacancy concentration in zirconia." Thesis, 1997. http://hdl.handle.net/1957/34055.
Full textGraduation date: 1998
Lin, Ching-Hsien, and 林京憲. "First-Principle Investigation on Oxygen Vacancy in High-K Dielectric Materials." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/18940294968448298313.
Full text國立高雄應用科技大學
電子工程系
97
Recently, the thickness of gate oxide made from SiO2 in nano-scale MOSFET has reached a physical limit according to the current leakage. The High-K dielectric materials have been found to be a good solution to the problem. However, there is a tradeoff between the dielectric constant and the energy gap in High-K materials, a larger dielectric constant usually associated with a smaller energy gap. To solve this problem a multilayer structure is adopted, for example a TiO2 grown on HfO2. In this work, an alloy oxide of Hf(1-X)TiXO2 is studied because the properties of TiO2 are complementary to HfO2. The density function theory (DFT) with the DMol3 and CASTEP codes is applied to investigate High-K alloy dielectric materials of Hf(1-X)TiXO2 and Hf(1-X)TiXOY. The mix-atom mode is used to model the alloy oxide. In out study, we find that (i) the position of minority atoms strongly affects the physical properties of bulk material, (ii) the high Ti concentration is easier to produce oxygen vacancies than the low concentration, and (iii) the increase of the Ti concentration decreases the energy gap but increases the dielectric constant. According to these properties, the Hf(1-X)TiXO2 may have possibility to be used as a High-K dielectric layer in nano-scale MOSFET.
Roh, Bumwook Macdonald Digby D. "Defect properties of anodic oxide films on titanium and impact of oxygen vacancy on oxygen electrode reactions." 2007. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-1878/index.html.
Full textHSIEH, TSU-HSIU, and 謝祖修. "High Sensitivity NO gas sensor using SnO2 nanofiber by oxygen vacancy engineering." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/43bha3.
Full textHuang, Cheng-Yen, and 黃丞言. "Studies of Oxygen Vacancy Defects and Magnetism in Co-Doped Cerium Oxide Nanoparticles." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/45604922345335992055.
Full textWang, Wen-Chieh, and 王玟捷. "Gigantic Enhancement in Sensing Ability of Nanowire Sensor by Increasing the Oxygen Vacancy Amounts." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/64488472717223223958.
Full text淡江大學
物理學系碩士班
101
Recently, there are many metal-oxide-based nano materials have been studied, most article indicated that the conductivity of the metal-oxide nano materials due to oxygen vacancies. In this research work, the SnO2-X and SnO2 nanostructures have been used to study the detection ability. The sensing abilities of metal-oxide-based nanosensors will be affected by the oxygen vacancy amounts of nanowire surface. In UV sensing, compared to the sensing abilities of SnO2 schottky contacted devices, the SnO2-X schottky contacted devices improved the sensitivity in different O2 concentration environment. The sensitivity and schottky barrier height variation with the increasement of O2 concentration of SnO2-X are much larger than SnO2, and the reset time is also faster. In gas sensing, the sensitivity of SnO2-X schottky contacted devices is better than SnO2 in different measurement temperature and different CO concentration. The response and reset time are faster, either. This result indicated that the sensing abilities can be gigantically enhanced by increasing the oxygen vacancy amounts. This research work provides a potential method for enhancing the detection ability of nanosensors.
Lin, Ching Hsuan, and 林敬軒. "Threshold Voltage Tuning and Oxygen Vacancy Passivation in FinFET by High-k/Metal Gate Processes." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/4tg64p.
Full text國立清華大學
工程與系統科學系
103
As device scaling, the leading edge technology is moving to FinFET process. In order to improve the FinFET performance, the thesis focuses on the study of High-k/metal gate process. There are three parts in this work to discuss the effects of High-k/metal gate process on device characteristics. In the first study, Vth tuning by the PMA process after MG-1 gate stack is investigated. The EWF, Vth, and other electrical characteristics are discussed. It is found that there are two mechanisms affecting the work function value during the PMA process. First, Work function (WF) could be lower by M1 diffusion. Second, work function could be higher by dipole formation. Therefore, the Vth can be modified by the PMA process. PMA X+100℃ is the best annealing condition for MG-1 gate stack, which shows the best electrical performance. In the second study, Vth tuning by different metal alloys (MG-2 vs. MG-1) is studied. (MG-1:Metal A and Metal C,MG-2:Metal B and Metal C) The thermal stability and electrical characteristics of two different metal alloys are discussed with the same PMA process. The results indicate that the thermal stability of Metal B is worse than that of Metal A. For MG-2 gate stack, PMA X℃ is the best annealing condition which shows good performance. For FinFET process, MG-1 as metal gate stack is better than MG-2. In the last study, O2 PDA at low temperature and low partial pressure are implemented; in order to passivate oxygen vacancy in High-k. The variation of Vth and Ion, CET, other electrical characteristics and reliability are discussed. The results show that CET of O2 PDA is a little higher than that of STD. For PFinFET, most device performance can be improved. Lower Vth variation is obtained, which indicates the oxygen vacancy can be passivated. However, the improvement of device performance (Vth, σVth, Ion) for NFinFET is not achieved. For NFinFET and PFinFET, the reliability can be improved by O2 PDA.
Yu, Shen-Wei, and 俞勝為. "Evaluation for Oxygen Vacancy on Co-Ce-Y Composite Oxides and Steam Reforming of Ethanol." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/78827177806809738326.
Full text國防大學理工學院
化學工程碩士班
102
The effect of accessible oxygen on the steam reforming of ethanol (SRE) over Co3O4-CeO2 and Co3O4-CeO2-Y2O3 catalysts was investigated. Both equal molar ratio of Co3O4-CeO2 catalysts were prepared by hydrothermal co-precipitation (H) and hydrothermal ultrasonic-assisted co-precipitation (UH) methods, and finally the UH method was applied to prepare 2.5, 5, and 10 wt % of yttrium-doped Co3O4-CeO2 catalysts, respectively. All catalysts were characterized through X-ray diffraction (XRD), temperature programmed reduction/temperature programmed oxidation (TPR/TPO), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HR-TEM), elemental analysis (EA) and CO2 - temperature programmed desorption (CO2-TPD) techniques at various stages. The results indicated that the incorporation of cobalt ion into the ceria lattice could increase the dispersion of ceria, oxygen vacancies and promote the oxygen-storing and releasing capability of ceria, especially over the catalyst prepared by ultrasonic-assisted method. The accessible oxygen played an important role on the SRE reaction and resistant to carbon deposition. The Co-Ce(UH) catalyst was more active and selective, i.e., ethanol conversion achieved complete and hydrogen selectivity (SH2) approached 90% at 400 C. The high oxygen storage capacity (OSC) and high accessible oxygen for the Co-Ce(UH) catalyst allowed oxidation/gasification of deposited carbon as soon as it formed, and less coke was detected. However, cobalt ions were not easily incorporated into CeO2 lattice with less formation of oxygen vacancies when the yttrium was added, which led to decrease of activity and more formation of carbonaceous deposits.
Jiu-XingHuang and 黃久倖. "Influence of oxygen vacancy reservoirs on resistive switching characteristics of oxide based resistance switching memories." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/33367771155989874222.
Full textYu-LungChung and 鍾裕隆. "Influences of oxygen vacancy drifting on resistive switching behaviors in TiOx and TaOx based nonvolatile memories." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/xkcv88.
Full text國立成功大學
材料科學及工程學系
103
This dissertation is devoted to study the influence of oxygen vacancy on resistive switching behaviors in the valence change memories (VCM) and electrochemical metallization (ECM) memories. The VCM and ECM memory devices were prepared with the device structures of Pt/TiOx/Pt/TiOx/Pt and Ag/TaOx/Pt, respectively. The current-voltage (I-V) characteristics including the electroforming, unipolar resistive switching (URS), bipolar resistive switching (BRS) and reset current characters were investigated and understood in terms of the migration of oxygen vacancies in VCM and ECM system. In the first part this dissertation, the TiOx-based memory devices were fabricated for electrical and material characterization. A distinct unipolar but single-polarity resistive switching behavior is observed in a TiOx/Pt/TiOx active layer, formed by thermal oxidation of a Ti/Pt/Ti stack. Introduction of the Pt mid-layer creates two additional Schottky barriers, which mediate the band bending potential at each metal-oxide interface and attains a rectifying current conduction at the high resistance state (HRS). Experimental evidences proving the single-polarity switching behavior is a combination of bias-induced Schottky barrier modification and conduction filament construction, both associated with the bias-driven migration of oxygen vacancies. In addition, the rectifying conduction behavior is also observed with an AFM-tip as the top electrode (TE), which implies the rectifying property is still valid when miniaturizing the device to nano-meter scale. In the second part of this dissertation, we explored the electroforming and resistive switching behaviors in the Ag/TaOx/Pt trilayer structure under a continual change of temperatures between 300 K and 100 K to distinguish the contributions of Ag ions and oxygen vacancies in developing of conducting filaments. We found that either electroforming or resistive switching, a significantly higher forming/set voltages is needed as the device is operated at 100 K, as compared to that observed when operating at 300 K. The temperature dependence of the pulsed switching time (tsw) measurement results indicates that larger activation energy (Ea) of Ag diffusion in TaOx (EaeV) will lead to a faster decay of Ag ions mobility in TaOx with decreasing temperature. Thus, the disparity in electroforming/set voltages of Ag/TaOx/Pt operating at 300 K and 100 K can attribute to the mobility difference of Ag ions at 300 K and 100 K. This mobility difference of Ag ions also leads a presence of metallic filament at 300 K while a filament composed of oxygen vacancy and Ag is formed at 100 K. The presence of oxygen vacancy segment in the conducting filament also modifies the reset current from a gradually descending behavior (at 300 K) to a sharp drop (at 100 K). Furthermore, the characteristic set voltage (Vset) and reset current are irreversible as the operation temperature is brought from 100 K back to 300 K, indicating the critical role of filament constituents on the switching behaviors of Ag/oxide/Pt system.
Chu, Fu Chuan, and 褚福荃. "Tuning oxygen vacancy distributions in High-K dielectric and scaling interfacial layer thickness for 16nm FinFET." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/q8s2eu.
Full text國立清華大學
工程與系統科學系
105
There are several challenges about gate dielectric thickness scaling in MOSFET, such as increased equivalent oxide thickness(EOT) value due to the growth of interfacial layer(IL)、reliability, and oxygen vacancies induced threshold voltage(Vt) variation. This thesis consists of three parts to discuss the impacts on characteristics of gate stack process of 16 nm FinFET, which are interfacial layer desorption by high temperature annealing to reduce IL thickness and defects、reducing Vt variation by passivaMetal nitrideg oxygen vacancy at interface and reducing EOT by incorporating few oxygen vacancy into high-K with modulating oxygen content in atomic layer deposition(ALD), and scavenging IL by increasing oxygen diffusion with a post metal annealing(PMA) and effects of PMA temperature and nitrogen gas flow ratio on metal cap. In the first parts, desorption of IL was carried out at high temperature for different annealing periods in N2 ambient. The desorption of IL in I/O FinFET can be obtained, which in confirmed by the reduced EOT. With increasing annealing time the on current and transconductance of devices increase. Reduced off current、enhanced mobility and reliability for PFinFET are achieved. The improvement may be attributed to the densification of IL after annealing. However, off current、subthreshold swing(S.S.), and mobility in NFinFET degrade after annealing. Which may be due to more diffusion in source draun junctions and defect generation at interface caused by a high temperature annealing. In the second part, high-K deposition is formed with different Oxygen precursor and Metal precursor cycle time in ALD to tune the oxygen vacancy distribution. Results of Core FinFET show that the EOT decreases, but S.S.、mobility and reliability degrade for sample with oxygen vacancy rich at both interface and bulk. Sample with oxygen vacancy deficiency at interface shows improved Vt variance 、off current and reliability, but increased EOT induced degraded S.S. and on current. Sample oxygen vacancy rich at interface shows the reduced Vt roll off、reduced Vt variation and S.S. , and improved reliability. The on current also increases due to reduced EOT. In the third part, PMA on metal nitride cap were performed at varies temperatures and gas ambients. EOT slightly increases with increasing anneal temperature and decreasing flow ratio of nitrogen gas, which induced S.S. and DIBL degradation. It may be attributed to interfacial layer regrowth with increasing the annealing temperature. IL regroeth caused by oxygen diffusion from metal nitride cap is more by decreasing nitrogen gas flow ratio in ambient.
Huang, Chien-Ming, and 黃千鳴. "First Principles Study of the Effect of Oxygen Vacancy and Mechanical Strain on the Photocatalytic Activity of Anatase TiO2." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/95510636079016948999.
Full text國立臺灣大學
材料科學與工程學研究所
98
This study tried to use First Principles to study the effects of induced oxygen vacancies and mechanical strain on formation energy of oxygen vacancies, electronic density of states, band structure and optic absorption coefficient. Our results showed that in oxygen defective TiO2, the relative sites of vacancies have strong influence on the interaction between vacancies, which leads to totally different electronic and optical properties. For different oxygen vacancy concentration, the tendency of oxygen vacancy configuration differs, and this also makes difference on the properties. For TiO2-x system, when x, the concentration of oxygen vacancy, increases, the optical absorption coefficient also increases. However, when x is larger than 0.125, the configuration tendency of oxygen vacancies switches from B-type to A-type, and this leads to higher probability of defect level. Defect level may become the recombination center of electron-hole pairs and the life time of carriers is largely shortened. This has negative effects on photovoltaic conversion. On the other hand, we also used First-Principles Calculations to study the effects of mechanical strain on thin film anatase TiO2. We discussed the stress parallel to (001), (010) and (101) planes. The mechanical strain we induced on the system is no larger than 8%. We use this system to discuss how the deformation that induced by lattice mismatch affects the electronic and optical properties. Our result shows that when the stress is parallel to (001) plane, the biaxial tensile stress on [010] and [100] direction and uniaxial tensile stress on [100] direction decreases the band gap, and the absorption spectrum shift toward longer wavelength side. We also found out that if we induce uniaxial compressive stress on [001] direction parallel to (010) plane or uniaxial tensile stress on [010] direction and uniaxial compressive stress on [1 ̅01] direction parallel to (101) plane, there will be similar results. Otherwise, there is no significant improvement on photocatalysis ability. Our results may give an aid to the process of TiO2 photocatalyst.
McCrate, Joseph Michael. "Characterization of low density oxide surface sites using fluorescent probes." 2013. http://hdl.handle.net/2152/23078.
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Lin, YungHsun, and 林詠勛. "Construction of the Carrier Concentration(Oxygen-Vacancy and Cation-Substitution) Separation Model & Metal Doping Effect on the Carrier Concentration in Conductive Oxides." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/02238829690685739233.
Full text國立中央大學
化學工程與材料工程研究所
99
In this thesis, we would propose a method which can decouple and estimate the oxygen-vacancy concentration and the cation-substitution concentration in an extrinsic metal oxide thin film separately. Also, we further propose how the properties of the dopant affect the cation-substitution reaction and the oxygen-vacancy concentration by observing the annealing ambient effects. In chapter 3, we propose the method which could estimate the oxygen-vacancy concentration and the cation-substitution concentration by measuring the carrier concentration of the thin film, which is annealed in different oxygen partial pressure. In chapter 4, we would discuss that how the difference of the electronegativity and the electron configuration would govern the cation-substitution reaction and the oxygen-vacancy formation reaction n. And how do oxygen-partial pressure and annealing temperature affect on the oxygen-vacancy concentration and the cation-substitution concentration. We found that the electronegativity would affect the cation-substitution concentration when the thin films were annealed at different oxygen pressure. And the electron configuration would affect the band diagram and affect the oxygen-vacancy formation energy. Besides the basic electrical properties, we also study the optical properties of ITO based thin films. In chapter 5, we found that the as-deposited ITO/Al structure would absorb particular light (400 nm- 600 nm) after thermal treatment. It is because the Al diffusion in ITO would locate at the interstitial site and serve as a defect level. Yet, we found that the pre-annealed ITO thin film is a good diffusion barrier layer which can retard the Al diffusion. On the other hand, by measuring the transmittance of the M:ITO thin films, we found that the transmittance of the extrinsic metal oxide in the near-UV region could be enhanced by doping the ternary metal. The transmittance of ITO thin film at near-UV region (380 nm) could be enhanced 22 % after doping Ti. Thus, after applying the Ti:ITO thin film on near-UV LED as the current spreading layer, the light output power of the near-UV LED is enhanced 52.1 %.
Mtangi, Wilbert. "Electrical characterization of process, annealing and irradiation induced defects in ZnO." Thesis, 2012. http://hdl.handle.net/2263/30356.
Full textThesis (PhD)--University of Pretoria, 2013.
Physics
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