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[pt] Esta tese investigou a síntese de metanol via hidrogenação do CO2 empregando dois conjuntos de catalisadores. O primeiro é composto pelos tradicionais catalisadores de Cu/ZnO/Al e o segundo aborda os catalisadores de In2O3 e ZrO2. Com relação ao Cu/ZnO/Al, foram preparados quatro amostras via coprecipitação. Os resultados mostraram que há um teor ótimo (3,8 por cento at.) de Al para a qual se observa uma maior taxa de formação de metanol. Os catalisadores foram caracterizados por fisissorção de N2, titulação com N2O,espectroscopia de absorção atômica, ICP, DRX, XPS, TPD-(CO2,NH3 e H2O), TPSR-CO2/H2, TEM/HRTEM/EDS. Uma correlação entre a taxa de formação de metanol e a quantidade de vacâncias de oxigênio superficiais do catalisador foi observada. Foi verificado que o Al atua como um promotor na geração de vacâncias de oxigênio. Com relação aos sistemas de In2O3, foi realizado um screening e selecionado nove catalisadores. Esses sólidos foram caracterizados pelas seguintes técnicas: DRX, TPD-NH3, TPD-CO2, TPR-H2 e TPSR-CO2/H2. Foi realizado um estudo em dinâmica molecular clássica investigando os efeitos da dopagem do In2O3 e da interação entre o In2O3 e o ZrO2 e relacionando os resultados com a performance dos catalisadores. O melhor desempenho catalítico foi obtido para o inédito catalisador de 0,6Pt-In2O3+6ZnZrO2, sendo esse desempenho associado à presença de vacâncias. Além disso, pelos cálculos teóricos de dinâmica molecular foi verificado que tanto a mistura física quanto a dopagem do In2O3 podem promovem a mobilidade de oxigênio da rede dos óxidos, o que facilita a formação de vacâncias de oxigênio. Sendo assim, os dois conjuntos de catalisadores estudados mostram que as vacâncias de oxigênio têm papel central na formação do metanol a partir da hidrogenação do CO2. As informações geradas neste trabalho contribuirão para o desenvolvimento de catalisadores promissores para a futura exploração industrial da geração de metanol a partir de CO2. / [en] This thesis investigated methanol synthesis via CO2 hydrogenation using two sets of catalysts. The first set consists of the traditional Cu/ZnO/Al catalysts and the second set involves In2O3 and ZrO2 catalysts. Concerning Cu/ZnO/Al, four samples were prepared via coprecipitation. The results showed that there is an optimum Al content (3.8 percent at.) for which a higher methanol formation rate is observed. The catalysts were characterized by N2 physisorption, titration with N2O, atomic absorption spectroscopy, ICP, XRD, XPS (CO2,NH3 and H2O)-TPD, CO2/H2-TPSR, TEM/HRTEM/EDS. A correlation was observed between the rate of methanol formation and the amount of surface oxygen vacancies on the catalyst. It was found that Al acts as a promoter in the generation of oxygen vacancies. Regarding the In2O3 systems, a screening was carried out and nine catalysts were selected. These solids were characterized using the following techniques: XRD, NH3- TPD, CO2-TPD, TPR-H2 and CO2/H2-TPSR. A classical molecular dynamics study was carried out investigating the effects of doping In2O3 and the interaction between In2O3 and ZrO2 and relating the results to the performance of the catalysts. The best catalytic performance was obtained for the new 0,6Pt-In2O3+6ZnZrO2 catalyst, and this performance was associated with the presence of vacancies. In addition, molecular dynamics calculations showed that both the physical mixture and the doping of In2O3 can promote the mobility of oxygen in the oxide lattice, facilitating the formation of oxygen vacancies. Thus, the two sets of catalysts studied show that oxygen vacancies play a central role in the formation of methanol from the hydrogenation of CO2. The information generated in this work will contribute to the development of promising catalysts for the future industrial exploitation of methanol generation from CO2.

[pt] Nos últimos anos, a crescente preocupação com o meio ambiente tem impulsionado o desenvolvimento de processos alternativos e sustentáveis para a obtenção de compostos importantes na indústria química. O isobuteno é um hidrocarboneto, comumente utilizado como intermediário para a síntese de diversos produtos, como polímeros e aditivos de combustíveis. A principal forma de produção desse hidrocarboneto é a partir do craqueamento da nafta, pelo qual é produzido como um coproduto por uma via dependente de fontes fósseis. Para atender à demanda de isobuteno associado a uma produção sustentável, novos estudos têm sugerido a síntese dessa olefina a partir da conversão catalítica de compostos como o etanol, uma matériaprima renovável que pode ser obtida a partir do processamento de diferentes biomassas. Experimentos recentes mostraram que uma mistura física In2O3+ZrO2 apresenta o mesmo desempenho de catalisadores In2O3/ZrO2, sendo ambos promissores para esse tipo de reação química. Assim, o objetivo deste estudo consiste em investigar esta mistura física como catalisador na síntese do isobuteno a partir do etanol. Nesta pesquisa, os catalisadores In2O3, ZrO2 e uma mistura física In2O3+ZrO2 foram avaliados por testes catalíticos em leito fixo e caracterizados pelas técnicas de DRX, XPS, EPR, TPD (CO, CO2, isopropanol, etanol e acetona), Fisissorção de N2, TPR-H2 e espectroscopia de infravermelho com adsorção de piridina. Os resultados revelam que a mistura física apresenta uma atividade catalítica superior ao In2O3 e ao ZrO2 puros, sendo capaz de formar isobuteno com uma seletividade de 36 por cento. O efeito sinérgico desses dois óxidos é verificado, resultando na formação de vacâncias catiônicas e aniônicas no catalisador MF, bem como promovendo as propriedades redox e básicas do sistema. / [en] In recent years, the growing concern with the environment has driven the development of alternative and sustainable processes to obtain important compounds in the chemical industry. Isobutene is a hydrocarbon commonly used as an intermediate for the synthesis of various products such as polymers and fuel additives. The main form of the production of this hydrocarbon is from the cracking of naphtha, by which it is produced as a co-product by a pathway dependent on fossil sources. To meet the demand for isobutene associated with sustainable production, new studies have suggested the synthesis of this olefin from the catalytic conversion of compounds such as ethanol, a renewable raw material that can be obtained from the processing of different biomasses. Recent experiments have shown that an In2O3+ ZrO2 physical mixture (MF) has the same performance as In2O3/ZrO2 catalysts, both of which are promising for this type of chemical reaction. Thus, the aim of this study is to investigate this physical mixture as a catalyst in the synthesis of isobutene from ethanol. In this research, the In2O3, ZrO2 catalysts and an In2O3+ZrO2 physical mixture were evaluated by fixed bed catalytic tests and characterized by the techniques of XRD, XPS, EPR, TPD (CO, CO2, isopropanol, ethanol and acetone), N2 physisorption, TPR-H2 and infrared spectroscopy with pyridine adsorption. The results show that the physical mixture has a catalytic activity superior to pure oxides, In2O3 and ZrO2, being able to form isobutene with a selectivity of 36 percent. The synergistic effect of these two oxides is verified, resulting in the formation of cationic and anionic vacancies in the MF catalyst, as well as promoting the redox and basic properties of the system.

Diluted magnetic semiconductor oxides (DMSOs) have received great attention recently due to their outstanding applications in optoelectronic and spintronic devices. Ever since the initial observation of ferromagnetism at room temperature in cobalt-doped titania, extensive effort is concentrated on preparation of transition metal doped wide band gap semiconductors, especially Mn- doped ZnO. Compared to Mn-doped ZnO, magnetic interactions in SnO! and In!O! semiconductors have been underexplored. SnO! and In!O! semiconductors have many applications, owing to their high charge carrier density and mobility as well as high optical transparency. Investigation on electronic structure changes induced by dopants during the synthesis procedure can effectively influence magnetic interactions between charge carriers. In this work, a combination of structural and spectroscopic methods was used to probe as-synthesized SnO! and In!O! nanocrystals doped with Mn!! and Mn!! as precursors. X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy are powerful techniques to explore formal oxidation state of manganese dopant, electronic environment, number of nearest neighbors around the absorbent, and bond lengths to the neighboring atoms. Analysis reveals the presence of multiple oxidation states in the doped nanocrystals, and establishes a relation between !"!! ratio and expansion or contraction of lattice parameters. !"!! Although doping semiconductors are crucial for manipulating the functional properties, the influence of dopants on nanocrystals structure is not well understood. Nanocrystalline films prepared from colloidal Mn-doped SnO! and In!O! nanocrystals through spin coating process exhibit ferromagnetic behavior in temperatures ranging from 5 K to 300 K. Magnetic transformation from paramagnetic in free-standing Mn-doped nanocrystals to strong ferromagnetic ordering in nanocrystalline films is attributed to the formation of extended structural defects, e.g., oxygen vacancies at the nanocrystals interface. Magnetic circular dichroism (MCD) studies clearly show that Mn!! occupies different symmetry sites in indium oxide, when bixbyite and rhombohedral In!O! nanocrystals (NCs) are compared.

Les "Oxydes Transparents et Conducteurs" (TCOs) possèdent une conductivité de type métallique tout en conservant, à l'état de films minces, une absorption négligeable dans tout le domaine visible. Malgré les recherches intensives menées durant ces 35 dernières années, il est nécessaire d'obtenir des TCOs avec de meilleures performances afin de répondre aux exigences des nouveaux dispositifs opto-électroniques. C'est dans cette optique que nous avons étudié des TCOs suivants sous forme de céramiques et de couches minces : (i) ATO et AZTO (symbolisant respectivement l'oxyde d'étain dopé à l'antimoine et l'oxyde d'étain co-dopé à l'antimoine et au zinc) ; (ii) IO (symbolisant l'oxyde d'indium) dopé avec des éléments spécifiques (résultats confidentiels) qui confèrent une conductivité électronique remarquable même lorsque le dépôt est réalisé sur substrat plastique. Dans le cas de AZTO, le co-dopage nous a permis d'obtenir des céramiques très denses et conductrices, sans perte d'antimoine lors du frittage. Par ailleurs, la conductivité électronique des films minces AZTO peut être modulée grâce au co-dopage. Ainsi nous pouvons proposer de nouveaux TCOs présentant des performances adaptées aux besoins d'applications spécifiques.

Diluted magnetic semiconductor oxides (DMSOs) have received great attention recently due to their outstanding applications in optoelectronic and spintronic devices. Ever since the initial observation of ferromagnetism at room temperature in cobalt-doped titania, extensive effort is concentrated on preparation of transition metal doped wide band gap semiconductors, especially Mn- doped ZnO. Compared to Mn-doped ZnO, magnetic interactions in SnO! and In!O! semiconductors have been underexplored. SnO! and In!O! semiconductors have many applications, owing to their high charge carrier density and mobility as well as high optical transparency. Investigation on electronic structure changes induced by dopants during the synthesis procedure can effectively influence magnetic interactions between charge carriers. In this work, a combination of structural and spectroscopic methods was used to probe as-synthesized SnO! and In!O! nanocrystals doped with Mn!! and Mn!! as precursors. X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy are powerful techniques to explore formal oxidation state of manganese dopant, electronic environment, number of nearest neighbors around the absorbent, and bond lengths to the neighboring atoms. Analysis reveals the presence of multiple oxidation states in the doped nanocrystals, and establishes a relation between !"!! ratio and expansion or contraction of lattice parameters. !"!! Although doping semiconductors are crucial for manipulating the functional properties, the influence of dopants on nanocrystals structure is not well understood. Nanocrystalline films prepared from colloidal Mn-doped SnO! and In!O! nanocrystals through spin coating process exhibit ferromagnetic behavior in temperatures ranging from 5 K to 300 K. Magnetic transformation from paramagnetic in free-standing Mn-doped nanocrystals to strong ferromagnetic ordering in nanocrystalline films is attributed to the formation of extended structural defects, e.g., oxygen vacancies at the nanocrystals interface. Magnetic circular dichroism (MCD) studies clearly show that Mn!! occupies different symmetry sites in indium oxide, when bixbyite and rhombohedral In!O! nanocrystals (NCs) are compared.

The idea of utilizing nanomaterials in bio-related applications has been extensively practiced during the recent decades. Magnetic nanoparticles (MPs), especially superparamagnetic iron oxide nanoparticles have been demonstrated as promising candidates for biomedicine. A protective coating process with biocompatible materials is commonly performed on MPs to further enhance their colloidal and chemical stability in the physiological environment. Mesoporous hollow silica is another class of important nanomaterials that are extensively studied in drug delivery area for their ability to carry significant amount of guest molecules and release in a controlled manner. In this study, different synthetic approaches that are able to produce hybrid nanomaterials, constituting both mesoporous hollow silica and magnetite nanoparticles, are described. In a two-step approach, pre-synthesized magnetite nanoparticles are either covalently conjugated to the surface of polystyrene beads and coated with silica or embedded/enclosed in the porous shell during a nanosized CaCO3 templated condensation of silica precursors, followed by acid dissolution to generate the hollow structure. It was demonstrated that the hollow interior is able to load large amount of hydrophobic drugs such as ibuprofen while the mesoporous shell is capable of prolonged drug. In order to simplify the fabrication procedure, a novel in-situ method is developed to coat silica surface with magnetite nanoparticles. By refluxing the iron precursor with mesoporous hollow silica nanospheres in polyamine/polyalcohol mixed media, one is able to directly form a high density layer of magnetite nanoparticles on silica surface during the synthesis, leaving reactive amine groups for further surface functionalization such as fluorescence conjugation. This approach provides a convenient synthesis for silica nanostructures with promising potential for drug delivery and multimodal imaging. In addition to nanoparticles, nanowires also benefit the research and development of instruments in clinical diagnosis. Semiconductive nanowires have demonstrated their advantage in the fabrication of lab-on-a-chip devices to detect many charge carrying molecules such as antibody and DNA. In our study, In2O3 and silicon nanowire based field effect transistors were fabricated through bottom-up and top-down approaches, respectively, for ultrasensitive bio- detection of toxins such as ricin. The specific binding and non-specific interaction of nanowires with antibodies were also investigated.

L'oxyde d'indium dopé à l'étain (ITO) présente une bonne transparence dans le visible<br />et une importante conductivité électrique. Ce travail est consacré à l'étude des performances<br />de films minces multicouches d'ITO obtenus par la voie sol-gel.<br />La microscopie électronique en transmission (MET) a permis d'analyser morphologie<br />et structure, et a mis en évidence pour la première fois la structure complexe de tels films solgel.<br />La MET et l'analyse par rétrodiffusion de particules α ont précisé la corrélation entre la<br />densité des multicouches, l'apparition de croûtes intermédiaires et la conductivité électrique<br />résultante.<br />Ce travail valide l'utilisation du recuit rapide pour la densification des films sol-gel en<br />comparaison avec un traitement classique.<br />Nous démontrons la potentialité de la voie sol-gel pour la croissance d'électrodes<br />d'ITO sur silicium poreux (SP). Les structures ITO/SP, pour lesquelles la photoluminescence<br />du SP est partiellement préservée, ont été étudiées en terme de diode Schottky.

<p>As  thefundamentallimits  of  two-dimensional(2D)geometric  scaling  of  commercial transistors  are  being reached,  there  is  tremendous  demand  for  new  materials  and  process innovations  that  can  keep  delivering  performance  improvements  for  future  generations  of computing chips. One major avenue being explored istheincorporation ofan increasing degree of three-dimensionality   by   vertically   stacking   logic   and   memory   layerswith   high-density interconnections.In  this  dissertation,  high-performanceultra-thin  amorphousindium  oxide transistors  are  demonstrated as  an  excellent  candidate  for these  back-end-of-line  (BEOL)  and monolithic 3D (M3D) integration applications.</p> <p>A  major  pain-point  in the  development  of  BEOL  and  M3D  systems is  the  strict  thermal budget imposed –once the bottom layer of devices is fabricated, they can generally withstand no more  than  400 °C.  It  is  exceedingly  difficult  to  directly  deposit  single-crystal  material  at  these temperatures, and polycrystalline materials will have grain boundary instability issues. Amorphous materials  generally  have  low  carrier  mobilities,  which  would  seemingly  remove  them  from contention as well. Indium oxideand itsclass of related metal oxides are exceptions. Indium oxideis  a  wide  bandgap  semiconductor  with  high  electron  mobility  up  to  about  100  cm²/V∙s  in amorphous form. Ithas a strong preference for native degenerate n-type doping which has hindered prior  devices  fabricated  with it.  In  this  dissertation,  extremely  thin  layers  on  the  order  of  1  nm thick are used for which quantum confinement effects widen the bandgap further, reliably enabling gate-controllable  carrier  densitiesand  demonstration  of  excellent  transistor  performance  with  a low thermal budget of just 225 °C.</p> <p>Detailed characterization is performed down to 40 nm channel lengths revealing excellent transistor characteristics  includingenhancement-mode operation withon currents greater than 2 A/μm, low  subthreshold  swing,and  high  on/off  ratios  due  to  the  wide  bandgap.  Subsequent chaptersdemonstrate the fundamental lower limits of off current around 6 ×10^-20A/μmby a novel measurement  technique,  good  gate  bias  stress  stability  behaviorwith  small  parameter  drift  at silicon  complementary  metal  oxide  semiconductor  (CMOS)  logic  voltages,  and  high-frequency operationin the GHz regime enabling easy operation at CMOS clock frequencies.</p>

Recently, there has been a growing interest in semiconductor and semiconducting oxide nanowires for applications in electronics, energy conversion, energy storage and optoelectronic devices such as field effect transistors, solar cells, Li- ion batteries, gas sensors, light emitting diodes, field emission displays etc. Semiconductor and semiconducting oxide nanowires have been synthesized widely by different vapor transport methods. However, conditions like high growth temperature, low vacuum, carrier gases for the growth of nanowires, limit the applicability of the processes for the growth of nanowires on a large scale for different applications. In this thesis work, studies have been made on the growth of semiconductor and semiconducting oxide nanowires at a relatively lower substrate temperature (< 500 °C), in a high vacuum (1× 10-5 mbar), without employing any carrier gas, by electron beam and resistive thermal evaporation processes. The morphology, microstructure, and composition of the nanowires have been investigated using analytical techniques such as SEM, EDX, XRD, XPS, and TEM. The optical properties of the films such as reflectance, transmittance in the UV-visible and near IR region were studied using a spectrophotometer. Germanium nanowires were grown at a relatively lower substrate temperature of 380-450 °C on Si substrates by electron beam evaporation (EBE) process using a Au-assisted Vapor-Liquid-Solid mechanism. High purity Ge was evaporated in a high vacuum of 1× 10-5 mbar, and gold catalyst coated substrates maintained at a temperature of 380-450 °C resulted in the growth of germanium nanowires via Au-catalyzed VLS growth. The influence of deposition parameters such as the growth temperature, Ge evaporation rate, growth duration, and gold catalyst layer thickness has been investigated. The structural, morphological and compositional studies have shown that the grown nanowires were single-crystalline in nature and free from impurities. The growth mechanism of Germanium nanowires by EBE has been discussed. Studies were also made on Silicon nanowire growth with Indium and Bismuth as catalysts by electron beam evaporation. For the first time, silicon nanowires were grown with alternative catalysts by the e-beam evaporation method. The use of alternative catalysts such as Indium and Bismuth results in the decrease of nanowire growth temperature compared to Au catalyzed Si nanowire growth. The doping of the silicon nanowires is possible with an alternative catalyst. The second part of the thesis concerns the growth of oxide semiconductors such as SnO2, Sn doped Indium oxide (ITO) nanowires by the electron beam evaporation method. For the first time, SnO2 nanowires were grown with a Au-assisted VLS mechanism by the electron beam evaporation method at a low substrate temperature of 450 °C. SEM, XRD, XPS, TEM, EDS studies on the grown nanowires showed that they were single crystalline in nature and free of impurities. The influence of deposition parameters such as the growth temperature, oxygen partial pressure, evaporation rate of Sn, and the growth duration has been investigated. Studies were also done on the application of SnO2 nanowire films for UV light detection. ITO nanowires were grown via a self-catalytic VLS growth mechanism by electron beam evaporation without the use of any catalyst at a low substrate temperature of 250-400 °C. The influence of deposition parameters such as the growth temperature, oxygen partial pressure, evaporation rate of ITO, and growth duration has been investigated. Preliminary studies have been done on the application of ITO nanowire films for transparent conducting coatings as well as for antireflection coatings. The final part of the work is on the Au-assisted and self catalytic growth of SnO2 and In2O3 nanowires on Si substrates by resistive thermal evaporation. For the first time, SnO2 nanowires were grown with a Au-assisted VLS mechanism by the resistive thermal evaporation method at a low substrate temperature of 450 °C. SEM, XRD, XPS, TEM, and EDS studies on the grown nanowires showed that they were single crystalline in nature and free of impurities. Studies were also made on the application of SnO2 nanowire films for methanol sensing. The self-catalytic growth of SnO2 and In2O3 nanowires were deposited in high vacuum (5×10-5 mbar) by thermal evaporation using a modified evaporation source and a substrate arrangement. With this arrangement, branched SnO2 and In2O3 nanowires were grown on a Si substrate. The influence of deposition parameters such as the applied current to the evaporation boat, and oxygen partial pressure has been investigated. The growth mechanism behind the formation of the branched nanowires as well as nanowires has been explained on the basis of a self-catalytic vapor-liquid-solid growth mechanism. The highlight of this thesis work is employing e-beam evaporation and resistive thermal evaporation methods for nanowire growth at low substrate temperatures of ~ 300-500 °C. The grown nanowires were tested for applications such as gas sensing, transparent conducting coatings, UV light detection and antireflection coating etc. The thesis is divided into nine chapters and each of its content is briefly described below. Chapter 1 In this chapter, a brief introduction is given on nanomaterials and their applications. This chapter also gives an overview of the different techniques and different growth mechanisms used for nanowires growth. A brief overview of the applications of semiconductors and semiconductor oxide nanowires synthesized is also presented. Chapter 2 Different experimental techniques employed for the growth of Si, Ge, SnO2, In2O3, ITO nanowires have been described in detail in this chapter. Further, the details of the different techniques employed for the characterization of the grown nanowires were also presented. Chapter 3 In this chapter, studies on the growth of Germanium nanowires by electron beam evaporation (EBE) are given. The influence of deposition parameters such as growth temperature, evaporation rate of germanium, growth duration, and catalyst layer thickness was investigated. The morphology, structure, and composition of the nanowires were investigated by XRD, SEM, and TEM. The VLS growth mechanism has been discussed for the formation of the germanium nanowires by EBE using Au as a catalyst. Chapter 4 This chapter discusses the growth of Si nanowires with Indium and Bismuth as an alternate to Au-catalyst by electron beam evaporation. The influence of deposition parameters such as growth temperature, Si evaporation rate, growth duration, and catalyst layer thickness has been investigated. The grown nanowires were characterized using XRD, SEM, TEM and HRTEM. The Silicon nanowires growth mechanism has been discussed. Chapter 5 This chapter discusses the Au-catalyzed VLS growth of SnO2 nanowires by the electron beam evaporation method as well as Antimony doped SnO2 nanowires by co-evaporation method at a low substrate temperature of 450 °C. The grown nanowires were characterized using XRD, SEM, TEM, STEM, Elemental mapping, HRTEM, and XPS. The effect of deposition parameters such as oxygen partial pressure, growth temperature, catalyst layer thickness, evaporation rate of Sn, and the growth duration of nanowires were investigated. The SnO2 nanowires growth mechanism has been explained. Preliminary studies were made on the possible use of pure SnO2 and doped SnO2 nanowire films for UV light detection. SnO2 nanowire growth on different substrates such as stainless steel foil (SS), carbon nanosheets films, and graphene oxide films were studied. SnO2 nanowire growth on different substrates, especially SS foil will be useful for Li-ion battery applications. Chapter 6 This chapter discusses the self catalyzed VLS growth of Sn doped Indium oxide (ITO) nanowires by the electron beam evaporation method at a low temperature of 250-400 °C. The grown nanowires were characterized using XRD, SEM, TEM, STEM, HRTEM, and XPS. The effect of deposition parameters such as oxygen partial pressure, growth temperature, evaporation rate of ITO, and the growth duration of the nanowires were investigated. Preliminary studies were also made on the possible use of self-catalyzed ITO nanowire films for transparent conducting oxides and antireflection coatings. ITO nanowire growth on different and large area substrates such as stainless steel foil (SS), and Glass was done successfully. ITO nanowire growth on different substrates, especially large area glass substrates will be useful for optoelectronic devices. Chapter 7 In this chapter, studies on the growth of SnO2 nanowires by a cost-effective resistive thermal evaporation method at a relatively lower substrate temperature of 450 °C are presented. The grown nanowires were characterized using XRD, SEM, TEM, HRTEM, and XPS. Preliminary studies were done on the possible use of SnO2 nanowire films for methanol sensing. Chapter 8 This chapter discusses the self-catalytic growth of SnO2 and In2O3 nanowires by resistive thermal evaporation. The nanowires of SnO2 and In2O3 were grown at low temperatures by resistive thermal evaporation using a modified source and substrate arrangement. In this arrangement, branched SnO2 nanowires, and In2O3 nanowires growth was observed. The grown nanowires were characterized using XRD, SEM, TEM, HRTEM, and XPS. The possible growth mechanism for branched nanowires growth has been explained. Chapter 9 The significant results obtained in the present thesis work have been summarized in this chapter.