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Shape memory alloys (SMAs) have been recognized as one of the most promising materials for MEMS micro-actuator applications. Among the available materials, Nickel/Titanium (NiTi) SMAs are more popular because, they exhibit unique properties in shape memory effect (SME) and pseudo-elasticity (PE). In addition NiTi SMA possesses high corrosion resistance, excellent mechanical properties and is also bio¬compatible. NiTi thin-film SMAs have been considered as the most significant material in the field of MEMS applications, which can be patterned with standard lithographic techniques to scale-up for batch production. However, the lack of proper understanding of basic materials’ properties and inability to reproduce, has limited the usage of this material in MEMS devices. The properties of NiTi SMA thin-films are very much sensitive to the elemental composition and structure, which are in turn decided by the deposition process and process parameters. A brief history of NiTi shape memory alloys (SMAs), basic information, transformation characteristics, crystal structure, phase diagram and literature reviewed for the current motivation have been presented in the second chapter In the third chapter, a brief summary about the deposition techniques relevant to NiTi film deposition has been presented. The deposition of NiTi films by a number of deposition techniques such as thermal evaporation, co-evaporation, molecular beam Epitaxy, pulsed laser deposition, flash evaporation, electron beam deposition, filtered arc deposition, ion beam assisted sputter deposition, vacuum plasma spraying, ion beam sputtering, ECR sputtering and magnetron sputtering techniques have been discussed. In order to achieve a precise control over film thickness and composition of the films on to the substrates, the selection of magnetron sputtering has been highlighted. In the present thesis, two prolonged approaches such as DC magnetron sputtering of an alloy target and co-sputtering of elemental targets have been presented. Various characterization techniques used for film thickness, composition, structure, micro¬structure, electrical, phase transformation and mechanical properties have also been briefly presented in the same chapter. In the fourth chapter, description of Conventional Alloy Target Sputtering System has been presented. DC magnetron sputtering of an alloy target with two different atomic ratios (Ni:Ti = 45:55 & 50:50) has been used for depositing the coatings. Several limitations in the reproducibility and repeatability have been observed with single alloy target sputtering, irrespective of the target composition ratio. In addition to this, incorporation of oxygen in the films during and after deposition has been observed, which has limited the extensive usage of this single alloy target system. The limitations regarding control over composition, thickness uniformity over large area have been improved by designing and fabricating a dedicated Three Target Magnetron Co-sputtering System. The vacuum diagnosis of the system under different conditions has been carried out by using PPR-200 Residual Gas Analyzer (RGA), which have included in Appendix I. Similar to alloy target sputtering system, the thickness uniformity and required composition with deposition parameters over a size of 75 mm diameter has been achieved and the process repeatability has been established. Oxygen incorporation in the films during deposition has been minimized by pre-sputtering of Ti target for known duration of time, which has resulted in significant reduction in partial pressure of oxygen in the chamber. The oxide layer formation on film surface has been eliminated by in-situ capping layer (TiN) deposition. In the fifth chapter, the influence of process parameters such as sample locations, substrate to target distance (STD), working pressure (WP), gas flow rates, deposition rates, deposition and annealing temperature, Target power, on the film thickness and composition uniformity have been presented for alloy target sputtering system as well as for the co-sputtering system. The film thicknesses have been measured with stylus method. Film compositions have been determined by energy dispersive X-ray spectroscopy (EDS), Secondary ion mass spectrometry (SIMS), Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS). The working pressure of 1.5 X 10-3 mbar, STD of 90 mm and target power of 100 W have been found to produce coatings having uniform thickness and composition over the given area for alloy target sputtering system. Similar investigations have been carried out for co-sputtered NiTiCu films. The working pressure of 1.5x 10-3 mbar, at a STD of 90 mm, at a rotational speed of 15 rpm and at target powers of 600, 50 and 12 W for Ti, Ni and Cu respectively, have resulted in the thickness and required composition uniformity over a size of 75 mm diameter substrate and the process repeatability has been established. In the Sixth chapter, the influence of process parameters on film structure and micro-structure on the NiTi/NiTiCu films deposited by a single alloy target and co¬sputtering have been studied by different analytical techniques like XRD, TEM, AFM, SEM etc. Phase transformation temperatures and kind of transformations have been investigated by DSC, Resistivity / Temperature and Stress/ Temperature studies and correlations have been established. The process parameters have been optimized for TiN deposition, which act as the capping layer to protect NiTi films from surface oxidation. The variation in mechanical behavior for the NiTi/ NiTiCu films before and after TiN capping by nano-indentation test have also presented. XRD and TEM studies have shown that the NiTi / NiTiCu films deposited at room temperature to 400o C are amorphous. Post-annealing, at a temperature of 450O C or above resulted in the film crystallization with oxide layer formation at the film surface, which has been confirmed by XRD and XTEM studies. In the case of Ni-rich NiTi films, R-phase diffraction peaks have also been identified in addition to the Austenite / Martensite phase. XRD investigations have shown that Ti-rich NiTi and Ni-rich NiTi films have resulted in precipitate free films. In the case of Ti-rich NiTiCu and Ni-rich NiTiCu films, the variations in Ti/Ni target power has resulted in the formation of NiTi 2 and Ni3Ti precipitates along with their parent Martensite and Austenite phases. When the Cu content is increased in NiTiCu films, an increase in number of Martensite phase diffraction peaks in XRD spectrum has been observed. XTEM studies have confirmed formation of oxide layer, inter-metallic layer and interface layer at higher post annealing temperatures. SEM studies have shown that the films deposited at higher gas flow rate results in the columnar micro-structure. In the context of NiTiCu films, the films deposited at higher Ti target power have shown more compact and tightly packed film micro-structure. AFM studies have shown increase in the average crystallite size and film roughness with post annealing temperature and duration. TiN coating has been used as the capping layer onto NiTi / NiTiCu films. Structural and micro-structural comparison of these films before and after TiN coating has resulted the appearance of (111) TiN peak in all TiN capped films. SEM and AFM studies have shown that the film roughness have decreased after capping layer deposition. DSC thermal cycling used to verify the film crystallization temperature has shown the appearance of exothermic peak in NiTi / NiTiCu films. DSC, Resistivity-temperature, stress-temperature response has been confirmed the transformation temperature and kind of transformations in all the films. Residual stress measurements have shown that the crystalline films exhibited lower bi-axial stress in comparison to the amorphous films. Ti-rich NiTi films have shown single phase transformations (M-A and A-M) whereas two phase transformations (M-R-A and A-R-M) have been observed in Ni-rich NiTi films. Higher deposition / annealing temperature have shown the appearance of distinct phase transformation peaks in resistivity vs. temperature studies. In the case of NiTiCu films, the decrease in film crystallization temperature with increase in the Cu content has been observed. The phase transformation temperature evaluated from second thermal cycle has shown decrease in the width of hysteresis loop with increase in the Cu content in NTC films. Nano-indentation studies have been carried out to evaluate the micro-hardness and modulus values of TiN capped and uncapped NiTi / NiTiCu films. The modulus and hardness uniformity have been confirmed for the different location over a diameter of 75 mm. The modulus and hardness values have increased with increase in the substrate and annealing temperature. Increase in the Cu target power has resulted in the increase in the hardness and modulus values under same deposition conditions. TiN coated NiTi / NiTiCu films have shown larger modulus and hardness values than the uncapped films. In the Seventh chapter, the fabrication process and actuation response for silicon dioxide, Aluminum and NiTi SMA coated micro-cantilevers has been discussed. Various nano-structures such as pyramids, beams and pillars by focused ion beam (FIB) micro-machining have been fabricated. High aspect ratio nano-pillars have been selected for micro-compression testing. In summary, this thesis emphasizes on the fabrication of specific sputtering systems relevant to NiTi film deposition and process parameter optimization for desired film thickness and composition uniformity. DC magnetron sputtering of a NiTi alloy target (50:50 and 45:55 at. %) and co-sputtering of elemental targets (Ni, Ti and Cu) have been presented. These films have been investigated for structural, micro-structural, phase transformation and mechanical properties. In-situ deposition of TiN capping layer, on to NiTi / NiTiCu films has been carried out to reduce the oxygen trapping. The fabrication process and actuation response of micro-cantilevers have been described. The etching characteristics to generate various nano-structures viz. pyramids, beams and pillars by focused ion beam (FIB) micro-machining have been investigated and mechanical testing of selected nano-structures have also been reported.

System on Chip (SoC) and System in Package (SiP) are two electronic technologies that involve integrating multiple functionalities onto a single platform. When the platform is a single wafer, as in SOC, it requires the ability to deposit various materials that enable the different functions on to an underlying substrate that can host the electronic circuitry. Transition metal oxides which have a wide range of properties are ideal candidates for the functional material. Si wafer on which micro-electronics technology is widely commercialized is the ideal host platform. Integrating oxides with Si, generally in the form of thin films as required by microelectronics technology, is however a challenge. It starts with the fact that the properties of crystalline oxides to be exploited in performing various functions are direction dependent. Thus, thin films of these oxides need to be deposited on Si in certain crystallographic orientations. Even if a suitably oriented Si wafer surface were available, it does not always provide for epitaxial growth a critical requirement for controlling the crystalline orientation of thin films. This is because Si surface is covered by an amorphous oxide of Si (SiOx). Thus, during growth of the functional oxide, an ambience in which the Si itself will not oxidize needs to be provided. In addition, during thin film growth on either Si or SiOx surface stresses are generated from various sources. Stress and its relaxation are also associated with the formation and evolution of defects. Both, stress and defects need to be managed in order to harness their beneficial effects and prevent detrimental ones. Given the requirement of SoC technology and the problem associated, the research work reported in this thesis was hence concerned with the precise controlling the stress and microstructure in oxide thin films deposited on Si substrates. In order to do so a versatile, ultra high vacuum (UHV) thin film with a base pressure of 10-9 Torr was designed and built as part of this study. The chamber is capable of depositing films by both sputtering (RF & DC) and pulsed laser ablation (PLD). The system has been designed to include an optical curvature measurement tool that enabled real-time stress measurement during growth. Doped zirconia, ZrO2, was chosen as the first oxide to be deposited, as it is among the few oxides that is more stable than SiOx. It is hence used as a buffer layer. It is shown in this thesis that a change in the growth rate at nucleation can lead to (100) or (111) textured films. These two are among the most commonly preferred orientation. Following nucleation a change in growth rate does not affect orientation but affects stress. Thus, independent selection of texture and stress is demonstrated in YSZ thin films on Si. A quantitative model based on the adatom motion on the growth surface and the anisotropic growth rates of the two orientations is used to explain these observations. This study was then subsequent extended to the growth on platinized Si another commonly used Si platform.. A knowledge of the stress and microstructure tailoring in cubic zirconia on Si was then extended to look at the effect of stress on electrical properties of zirconia on germanium for high-k dielectric applications. Ge channels are expected to play a key role in next generation n-MOS technology. Development of high-k dielectrics for channel control is hence essential. Interesting stress and property relations were analyzed in ZrO2/Ge. Stress and texture in pulsed laser deposited (PLD) oxides on silicon and SrTiO3 were studied. It is shown in this thesis that stress tuning is critical to achieve the highest possible dielectric constant. The effect of stress on dielectric constant is due to two reasons. The first one is an indirect effect involving the effect of stress on phase stability. The second one is the direct effect involving interatomic distance. By stress control an equivalent oxide thickness (EOT) of 0.8 nm was achieved in sputter deposited ZrO2/Ge films at 5 nm thickness. This is among the best reported till date. Finally, the effect of growth parameters and deposition geometry on the microstructural and stress evolution during deposition of SrTiO3 on Si and BaTiO3 on SrTiO3 by pulsed laser deposition is the same chamber is described.

M. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / In chemical bath deposition (CBD) method, deposition of metal chalcogenide semiconducting thin films occurs due to substrate maintained in contact with a dilute chemical bath containing metal and chalcogenide ions. Semiconducting nickel sulphide (NiS) and iron sulphide (FeS) thin films have been prepared on a glass substrate by varying the deposition parameters such as the concentration of solutions, deposition time, temperature and pH. Multi-layered thin films were deposited on glass substrate and the spin-cast conductive polymer, poly (3.4-ethylenedioxythiopene) polystyrene sulfonate (PEDOT: PSS) was intercalated. The characterization of the films was carried out using UV-Vis spectroscopy, scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM) and X-ray diffraction (XRD). Single layer nickel sulphide was deposited at room temperature, pH 10 and the deposition period of 3 hours, triethanolamine was used as the complexing agent. Iron sulphide was deposited for 6 hours at 70 °C with the pH of 2.5 using EDTA as a complexing agent. Generally the iron and nickel sulphide were prepared from their respective nickel or iron salt and the thiourea or thiosulfate as a source of sulphide ions in solution. SEM and AFM results show that the FeS film is evenly coated and has uniform grain size with the roughness of ~22.4 nm and thickness of ~23.8 nm. The optical absorption analysis of FeS showed the band gap energy of ~2.9 eV which blue shifted from the bulk. The EDX analysis confirms the compositions of iron and sulphur in FeS films. XRD pattern showed amorphous films for both FeS and NiS thin films due to the amorphous nature of the glass substrate. The optical data of NiS film were analysed and exhibited the band gap energy of ~3.5 eV and ~3.3 eV for successive ionic layer adsorption and reaction (SILAR), which is the modified CBD, both blue shifted from the bulk. The films were observed to have thickness value of ~35.7 nm and ~2.3 nm SILAR with the roughness of ~112.5 nm and ~35.4 nm SILAR from AFM results. SEM confirmed the uniformly distributed film presented by AFM analysis. The chemical composition of Ni and S were confirmed by EDX spectra. The PEDOT: PSS was intercalated between the FeS as the first layer and NiS as the top layer which gave the thickness of ~18.7 nm and roughness of ~115.2 nm from AFM analysis. PEDOT: PSS acted as a passive layer that protects and stabilize the FeS layer and NiS as the third active layer which enhanced the optical absorption of the film when using SILAR method for solar application.

L’émergence des satellites très haut débit pour la couverture des zones rurales s’accompagne de nombreuses contraintes technologiques. Dans le cadre du plan France très haut débit, le projet THD-sat proposé par le CNES se base sur l’utilisation des bandes Q et V pour assurer les liaisons avec les stations au sol et libérer de la ressource sur la bande Ka communément utilisée par les satellites ancienne génération. Avec la montée en fréquence, les besoins en termes de filtrage deviennent très stricts nécessitant des considérations particulières. Le premier chapitre reprend le contexte de l’étude et expose les différents éléments permettant de justifier le choix de la technologie SIW qui profite à la fois des bons facteurs de qualité des modes volumiques se propageant dans le substrat et de l’aisance du procédé technologique et de l’intégration des structures planaires. Les performances des cavités SIW restent néanmoins intimement liées à l’épaisseur de substrat qui doit être augmentée pour atteindre de meilleurs facteurs de qualité. L’augmentation de l’épaisseur de substrat s’accompagne de deux principales limitations : le rallongement des fils de « bonding » utilisés pour le câblage du filtre à son environnement MIC d’épaisseur 254 μm et l’élargissement de la ligne d’accès 50 Ω induisant des problèmes de discontinuités et d’excitations de modes parasites. L’approche suivie consiste à considérer des formes 3D permettant l’adaptation de mode et d’épaisseur entre une ligne microruban sur substrat de 254 μm d’épaisseur et le SIW d’épaisseur plus importante. Une nouvelle transition 3D est dès lors imaginée. Le chapitre II reprend les différents procédés technologiques utilisés pour la mise en forme et la métallisation des substrats 3D. Les substrats considérés sont l’alumine et la silice fondue mis en forme par ablation laser et le thermoplastique COP mis en forme par moulage. La principale limitation de l’ablation laser concerne les épaisseurs de substrat accessibles. Nous nous limitons à 635 μm dans le cas de l’alumine et à 500 μm dans le cas de la silice fondue. Le moulage polymère permet de s’affranchir de cette limitation et de viser des substrats plus épais (2 mm pour la solution COP).Le chapitre III reprend les étapes de conception des différentes solutions de filtrage avec la nouvelle transition 3D. Des résultats de mesures de différents prototypes réalisés sont par ailleurs présentés. Ces résultats sont globalement encourageants mais nécessitent d’être davantage développés pour être mieux exploitables. / The emergence of satellite high-speed internet for the coverage of rural zones is accompanied by numerous technological constraints. The current trend is to use higher frequency bands to release the satellite capacity for users. The increasing frequency requires new considerations especially for filtering needs which become notably strict in terms of performance and integration in small integrated circuits. This work introduces filtering solutions based on high quality factor Substrate Integrated Waveguides (SIW) using a novel 3D transition for a better integration in widely planar Hybrid ICs.The first chapter introduces the study’s context and the different elements justifying the use of the SIW technology.In fact, these structures profit from both the good quality factors of TE-modes propagating in the substrate and the easy fabrication process and integration of planar circuits. However, to increase the SIW quality factor, the substrate’s height should be increased which induces interconnection limitations such as long bond wires with high parasitic effects and large microstrip access lines with discontinuity problems and the propagation of parasitic modes. The adopted approach consists in imagining 3D shapes providing both mode and thickness matching between a microstrip line etched on a thin substrate and a high substrate SIW.The second chapter introduces the different manufacturing processes used for the substrate’s shaping and metallization. Three substrates are considered: Alumina, fused Silica and Cyclo Olefin Polymer COC. Alumina is widely used in space applications and has a well-mastered process. For equivalent dielectric losses, fused silica has a lower permittivity for bigger structures with less manufacturing tolerance sensitivity. Both Alumina and fused silica substrates are shaped using a laser ablation. The reachable substrate’s height using this machining method is relatively low. The polymer solution (COP) is elaborated using a molding process allowing higher substrates heights.The last chapter outlines the design steps of the different solutions and the measurement results of the first prototypes. These results are on the whole encouraging but require further development.

Grâce à ses excellentes propriétés physiques et chimiques (stable thermiquement, bon conducteur électrique et de chaleur, ductile, très dur mécaniquement, bonne inertie chimique), le matériau tantale et son nitrure TaNx sont utilisés comme revêtement de surface des outils, résistance électrique, barrière de diffusion au cuivre, croissance de nanotubes par un procédé chimique catalytique en phase vapeur. C’est ce matériau et son nitrure que nous avons étudiés lors de cette thèse.Aujourd’hui les exigences des industriels nécessitent que la pulvérisation cathodique magnétron (PCM) puisse être appliquée aux pièces de formes complexes. La principale limitation de cette méthode de dépôt est que la plupart des particules pulvérisées sont neutres. Pour contrôler l’énergie et la trajectoire des particules pulvérisées, des nouveaux procédés IPVD (Ionized Physical Vapor Deposition) ont été développés pour ioniser les atomes pulvérisés. Le procédé RF-IPVD (Radio-Frequency Ionized Physical Vapor Deposition) permet, grâce à une boucle placée entre la cible et le substrat et polarisée en RF, de créer un second plasma permettant d’ioniser la vapeur pulvérisée. Un autre procédé a été développé : nommé HIPIMS (High Power Impulse Magnetron Sputtering), ce procédé utilise une alimentation fournissant des impulsions de courte durée et de forte puissance au lieu d’une alimentation DC. Les particules pulvérisées peuvent être ionisées dans le plasma magnétron qui est très dense lors des impulsions. Nous avons réalisé des couches minces de Ta par PCM, RF-IPVD et HIPIMS, et des couches minces de TaNx par PCM et HIPIMS. Les différentes propriétés des décharges et des couches minces sont étudiées et comparées dans ce mémoire. / Thanks to their excellent physical and chimical characteristics such as good stability with temperature, good conductor of heat and electricity, ductility, hardness, chemical inertness and good corrosion resistance, tantalum and its nitride are used in a wide variety of applications such as wear and corrosion-resistant materials, thin film transistors, diffusion barrier for copper and for carbon nanotube grown by CCVD process (catalytically chemical vapor deposition). For some recent industrial demand, it is necessary to deposit on substrates with complex shape. The main disadvantage of the conventional magnetron sputtering (CMS) is that most of the sputtered particles are neutral. To controle the energy and the path of sputtered particles, new magnetron sputtering techniques have been developed for ionizing a significant fraction of sputtered material. A new sputtering process called RF-IPVD consists in ionizing the sputtered vapor by adding second plasma by a RF coil between the target and the substrate. Another method called HIPIMS (High Power Impulsed Magnetron Sputtering), uses high power impulse instead of DC power. During the impulse, the sputtered Ta atoms are ionized in the dense plasma. We have deposited Ta thin films by CMS, RF-IPVD and HIPIMS and TaNx thin films by CMS and HIPIMS. The objective of this thesis is to compare the properties of discharges and thin films deposited by these different techniques.

Today there is a great deal of interest in the development of gas sensors for various applications like monitoring of toxic gases, detection in oil reservoirs, mines, homes etc. Solid-state gas sensors have many advantages over the conventional analytical methods and hence are widely used. Amongst them, semiconducting metal-oxides based sensors are popular due to many advantages like low cost, small size, high sensitivity and long life. The present thesis reports a detailed work of TiO2 (Titania) thin film fabrication based on sol-gel method, study of their crystallization behavior and surface morphology, and characterizing them for alcohol sensing properties Sol-gel method is a wet chemical technique with many advantages over the conventional methods and offers a high degree of versatility to modify the film properties. Titania thin films were made with titanium isopropoxide as the precursor and ethanol and isopropanol as the solvents. Also effect of surfactants(PEG and CTAB) on the sol properties and film properties have experimentally examined. A in-house gas sensor testing setup has been designed and fabricated to characterize the sensors. Sensors with three different electrode configurations and also two different electrode material have been tested. The electrode geometry and material play a significant role on the sensing behavior and results for the same have been discussed.

The research in permanent magnet thin films focuses on the search of new materials and methods to increase the prevalent data storage limit. In the recent past the work towards the application of these films to micro systems have also gained momentum. Materials like samarium cobalt with better magnetic properties and temperature stability are considered to be suitable in this regard. The essential requirement in miniaturization of these films is to deposit them on silicon substrates that can alleviate the micro fabrication process. In this work, an effort has been made to deposit SmCo films with better magnetic properties on silicon substrates. In the deposition of SmCo, the composition of the deposited films and the structural evolution are found to play an important role in determining the magnetic properties. Proper control over these parameters is essential in controlling the magnetic properties of the deposited films. SmCo being a two component material the composition of the films is dependent on the nature of the source and the transport of the material species from source to substrate. On the other hand, structural evolution is dependent on the energetical considerations between the SmCo lattice and substrate lattice. This most often is dominated by the lattice match between the condensing lattice and the substrate lattice. As such Si does not provide good lattice match to SmCo lattice. Hence suitable underlayers are essential in the deposition of these films. Materials like W, Cu, Mo and Cr were used as underlayers. Out of all these Cr is found to provide good lattice match and adhesion to SmCo lattice. Sputtering being the common deposition tool, SmCo could be sputtered either from the elemental targets of Sm and Co or from the compound target of SmCo5. Sputtering of elemental targets of Sm and Co provides the flexibility of varying the composition whereas sputtering from the SmCo alloy target provides to flexibility of controlling the structural evolution by different process parameters. In this work two different techniques namely Facing Target Sputtering (FTS) and Ion Beam Sputter Deposition (IBSD) were followed in depositing SmCo films. In FTS technique, SmCo films were directly deposited on silicon substrates by simultaneous sputtering of samarium and cobalt targets facing each other. This sputtering geometry enabled to achieve films with a wide composition range of 55 – 95 at. % of cobalt in single deposition. The resulting composition variation and material property variation were investigated in terms of process parameters like pressure, temperature, SubstrateTarget Distance (STD) and InterTarget Distance (ITD). The composition distribution of the films was found to be dependent on the thermalisation distances and the mean free path available during the transport. To explain the process and the composition variation, a simulation model based on Monte Carlo method has been employed. The simulated composition variation trends were in good agreement with that of the experimental observations. IBSD, known for its controlled deposition, was employed to deposit both Cr (as an underlayer) and SmCo films. Cr with close epitaxial match with SmCo induces structural evolution in deposited films. The initial growth conditions were found to play a dominant role in the structural evolution of these Cr films. Hence, initial growth conditions were modified by means of oblique incidence and preferential orientation of (200) plane was obtained. With three different angles of incidence, three different surface orientations of Cr films were achieved. These films were then used as structural templates in the deposition of SmCo films. The influence of parameters like composition, impurities, film thickness, beam energy, ion flux, annealing, angles of incidence and underlayer properties on the structural and magnetic properties of SmCo was studied. The structural evolution of SmCo has been found to depend on the structural orientation of Cr underlayers. This followed the structural relation of SmCo(100)||Cr(110)||Si(100) and SmCo(110)||Cr(100)||Si(100). A mixed surface plane orientation was observed in the case of mixed orientation Cr template. The magnetic coercivities were found to increase from 50 Oe to 5000 Oe with the change in the structure of the deposited films.

The thesis consists of two parts. Part 1 deals with the preparation of thin films and sub-micron powders of complex metal oxides by nebulized spray pyrolysis (NSP) and Part 2 consists of Brillouin scattering studies of solid materials exhibiting interesting phase transitions. The simple technique of NSP has been employed to prepare thin films of A12O3, PbTiO3, Pb(Zr0.5Ti0.5)O3 (PZT) and PbZrO3 on single crystal substrate. The films were characterized by various techniques for their composition, structure, morphology and dielectric properties. Ferroelectric (FE) films of the configuration FE/LaNiO3/SiO2/Si (FE = PbTiO3 and PZT), wherein the LaNiO3 barrier electrode was also deposited on the SiO2/Si substrate by NSP, have been investigated. The films exhibit satisfactory ferroelectric properties. PbZrO3 films deposited on LaNiO3/SiO2/Si substrates show good features, including a reversible AFE ↔ FE transition. Sub-micron particles of TiO2, ZrO2, Pb(Zr0.5Ti0.5)O3, Al2O3, S1O2 and mullite have been prepared by NSP and characterized by various techniques. Brillouin scattering has been used, for the first time, not only to characterize the Peierls transition but also the incommensurate to commensurate transition in the one-dimensional blue bronze, K0.3M0O3. The charge density wave transition in NbSe2 has also been investigated by Brillouin scattering. The charge ordering and antiferromag-netic transitions in single crystals of the rare earth manganates, Nd0.5Ca0.5MnO3 and Pr0.63Ca 0.37MnO3, have been investigated by Brillouin scattering. It is noteworthy that the temperature variation of the Brillouin shift and intensity parallel to that of the magnetization, thereby throwing light on magnetic excitations in charge-ordered state. Brillouin scattering investigations of C60 and C70 films have yielded values of the elastic moduli.

Today there is a great deal of interest in the development of gas sensors for applications like air pollution monitoring, indoor environment control, detection of harmful gases in mines etc. Based on different sensing principles, a large variety of sensors such as semiconductor gas sensors, thermoelectric gas sensors, optical sensors and thermal conductivity sensors have been developed. The present thesis reports a detailed account of a novel method followed for the design and development of a thermoelectric gas sensor for sensing of Volatile Organic Compounds. Thermoelectric effect is one of the highly reliable and important working principles that is widely being put into practical applications. The thermoelectric property of semiconducting tin oxide film has been utilized in the sensor that has been developed. The thermoelectric property of semiconducting tin oxide film has been utilized in the sensor. The deposition parameters for sputtering of tin oxide film have been optimized to obtain a high seebeck coefficient. A test set-up to characterize the deposited films for their thermoelectric property has been designed and developed. A novel method of increasing the seebeck coefficient of tin oxide films has been successfully implemented. Thin films of chromium, copper and silver were used for this purpose. Deposition of the semiconducting oxide on strips of metal films has led to a noticeable increase in the seebeck coefficient of the oxide film without significantly affecting its thermal conductivity. The next part of our work involved development of a gas sensor using this thermoelectric film. These sensors were further tested for their response to volatile organic compounds. The sensor showed significant sensitivity to the test gases at relatively low temperatures. In addition to this, the developed sensor is also selective to acetone gas.