Solar absorber coatings are one of the key components in concentrated solar power (CSP) plants. Currently operating at temperatures up to 565°C and suffering from emissive losses, their energy conversion efficiency could be improved by applying high-temperature stable materials with solar selective properties, i.e. high absorptivity and low emissivity. In this work, the transparent conductive oxide (TCO) SnO2:Ta is developed as a solar selective coating (SSC) for CSP absorbers. Starting with simulations covering basic requirements for SSCs, the deposition process of SnO2:Ta is optimized and extensive optical characterization and modelling are performed. It is shown that upon covering with a SiO2 antireflective layer, a calculated absorptivity of 95% and an emissivity of 30% are achieved for the model configuration of SnO2:Ta on top of a perfect black body (BB). High-temperature stability of the developed TCO up to 800 °C is shown in situ by spectroscopic ellipsometry and Rutherford backscattering spectrometry. The universality of the concept is then demonstrated by transforming silicon and glassy carbon from non-selective into solar selective absorbers by depositing the TCO on top of them. Finally, the energy conversion efficiencies ηCSP of SnO2:Ta on top of a BB and an ideal non-selective BB absorber are compared as a function of solar concentration factor C and absorber temperature TH.

In dieser Dissertation wurde die Beziehung zwischen den strukturellen, optischen und Ladungstransporteigenschaften von dotierten ZnO- und Zn1-xMgxO-Schichten eingehend untersucht. Das Ziel war es, die oben genannten Zusammenhänge weiter aufzuklären, wodurch sich anschließend Ansätze für eine zielgerichtete Verbesserung der Schichteigenschaften ableiten lassen. Zunächst konzentriert sich die Arbeit auf das Wachstum der ZnO-Schichten, um wichtige strukturelle Parameter, wie zum Beispiel Korngrößen und Defektdichten, mittels Röntgendiffraktometrie und Transmissionselektronenmikroskopie zu bestimmen. Diese strukturellen Parameter wurden dann als Modellparameter für die theoretische Modellierung des Transports der freien Ladungsträger verwendet. Temperaturabhängige Hall-, Leitfähigkeits- und Seebeck-Koeffizient-Messungen zeigten, dass der elektrische Transport hauptsächlich durch die Streuung der Ladungsträger an ionisierten Störstellen und Korngrenzen limitiert wird. Im Rahmen dieser Arbeit wurde die theoretische Beschreibung der Streuung an Korngrenzen auf entartet dotierte Halbleiter erweitert. Diese Ergebnisse wurden dann genutzt, um ein qualitatives Modell zu formulieren, welches den Zusammenhang zwischen dem Magnetron-Sputter-Abscheidungsprozess und den strukturellen und elektrischen Eigenschaften der Schichten herstellt. Gemäß diesem Modell sind die Schichteigenschaften bei niedrigen Abscheidungstemperaturen hauptsächlich durch die Bildung akzeptoratiger Sauerstoffzwischengitterdefekte bestimmt, die einen Teil der extrinsischen Dotanden kompensieren. Diese Defekte werden durch ein Bombardement der wachsenden Schicht mit hochenergetischen negativen Sauerstoffionen verursacht. Bei höheren Abscheidungstemperaturen dominiert die Bildung von sekundären Phasen oder Defektkomplexen, in denen der Dotant elektrisch inaktiv ist. / In this thesis, the relation between the structural, optical, and charge carrier transport properties of magnetron sputtered doped ZnO and Zn1-xMgxO films has been investigated in detail. The objective was to clarify the above mentioned relations, which allows to derive solutions for a deliberate improvement of the layer properties. The work first focusses on the growth of the ZnO layers to determine important structural properties like grain sizes and defect densities via X-ray diffraction and transmission electron microscopy investigations. These structural properties were then used as model parameters for the theoretical modelling of the charge carrier transport. The temperature dependent Hall, conductivity and Seebeck coefficient measurements show that the transport is mainly limited by grain boundary scattering and ionized impurity scattering. The theoretical description of the grain boundary scattering has been extended in this work to also include degenerate semiconductors. Based on the results on the structural and electronic properties, in a next step a qualitative model was developed which explains the correlation between the magnetron sputtering deposition process and the structural and electronic properties of the films. According to this model, the properties of the films are mainly influenced by the formation of electrically active acceptor-like oxygen interstitial defects at low deposition temperatures, which lead to a partial compensation of the extrinsic donors. These defects are caused by a bombardment of the growing film by high-energetic negative oxygen ions. At higher deposition temperatures, the formation of secondary phases or defect complexes, in which the dopant is electrically inactive, prevails.

Die vorliegende Arbeit beschreibt einen neuartigen Fügeprozess, das sogenannte reaktive Fügen bzw. Bonden. Hierbei werden sich selbsterhaltene exotherme Reaktionen in nanoskaligen Schichtsystemen als lokale Wärmequelle für das Fügen unterschiedlichster Substrate der Mikrosystemtechnik verwendet. Das Bonden mit den reaktiven Systemen unterscheidet sich von herkömmlichen Verfahren der Aufbau- und Verbindungstechnik primär dadurch, dass durch die rasche Reaktionsausbreitung bei gleichzeitig kleinem Reaktionsvolumen die Fügetemperaturen unmittelbar auf die Fügefläche beschränkt bleiben. Entgegen den herkömmlichen Fügeverfahren mit Wärmeeintrag im Volumen, schont das neue Verfahren empfindliche Bauteile und Materialien mit unterschiedlichsten thermischen Ausdehnungskoeffizienten lassen sich besser verbinden. In der vorliegenden Arbeit werden die Grundlagen zur Dimensionierung, Prozessierung und Integration der gesputterten reaktiven Materialsysteme beschrieben. Diese Systeme werden verwendet, um heterogene Materialien mit unterschiedlichen Durchmessern innerhalb kürzester Zeit auf Wafer-Ebene und bei Raumtemperatur zu bonden. Die so erzeugten Verbindungen werden hinsichtlich der Mikrostruktur, der Zuverlässigkeit sowie der Dichtheit untersucht und bewertet. Zusätzlich wird die Temperaturverteilung in der Fügezone während des Fügeprozesses mit numerischen Methoden vorhergesagt.

This thesis deals with the analysis of nano-structured layers deposited by high-frequency magnetron sputtering on the monocrystalline silicon surface. The content of the work focuses on the magnetron sputtering application as an alternative method for passivation and antireflection layers deposition of silicon solar cells. The procedure of pre-deposite silicon surface cleaning by plasma etching in the Ar/H2 gas mixture atmosphere is suggested. In the next step the silicon nitride and aluminum nitride layers with hydrogen content in Ar/N2/H2 gas mixture by magnetron sputtering are deposited. One part of the thesis describes an experimental pseudo-carbide films deposition from a silicon target in the atmosphere of acetylene (C2H2). An emphasis is placed on the research of sputtered layers properties and on the conditions on the silicon-layer interface with the help of the standard as well as special measurement methods. Sputtered layers structure is analyzed by modern X-ray spectroscopy (XPS) and by Fourier infrared spectroscopy (FTIR). Optical ellipsometry and spectrophotometry is used for the diagnostic of the layers optical properties depending upon the wavelength of incident light. A special method of determining the surface lay-out of the charge´s carrier life in the volume and on the surface of silicon is employed to investigate the passivating effects of the sputtered layers.

Les films de nitrures métalliques nanostructurés sont généralement utilisés comme revêtements protecteurs. Ti1-xAlxN (0 ≤ x ≤ 1) peut être considéré comme un système modèle, où TiN (cubique) et AIN (hexagonal) sont partiellement miscibles. L’élaboration par dépôt physique en phase vapeur donne au film une microstructure colonnaire complexe composée de phase métastable pouvant cohabiter avec des précipités localisés aux joints de grains. Une haute dureté et une grande résistance à l’oxydation sont observées pour un maximum d’atomes de Ti substitué par des atomes de Al en réseau cubique. Les conditions de dépôt et la composition jouent un rôle majeur sur la substitution des éléments métalliques (Ti ,Al). Nous avons préparé deux séries de films déposés par pulvérisation cathodique magnétron réactive à partir de cibles TiAl compartimentées et frittées. La micro- et nanostructure des films ont été analysées par Diffraction, Spectroscopie d’Absorption des rayons X et Microscopie Electronique à Transmission. L’usure des revêtements a été étudiée par microtribologie. Nous observons pour les films riches en Ti (x < 0,5) des directions de croissances [200]c et [111]c, caractéristiques d’un réseau cubique. Tandis que, les films riches en Al (x > 0,7) présentent une croissance de domaines bien cristallisés suivant la direction [002]h du réseau hexagonal. De plus, nous avons mis en évidence l’apparition de la transition cubique / hexagonal à des teneurs en Al plus élevée pour les films issus de cible frittée. Ces films montrent une meilleure résistance à la fissuration et à l’usure que ceux déposés à partir de cible compartimentées. / Ti1-xAlxN (0 ≤ x ≤ 1) is considered as a model system, where TiN (fcc) and AlN (hcp) do not mix over the whole composition range due to their low miscibility. However, the physical vapour deposition (PVD) allows achieving metastable phases of Ti1-xAlxN, where Al atoms are partially substituting for Ti in fcc lattice. Ti1-xAlxN coatings exhibit high hardness and oxidation resistance for the maximum Al substituted to Ti in fcc lattice (about x=0.6). The proportion of grain boundaries and the limit solubility play a major role on the mechanical properties and resistance to wear of the coatings. Several techniques are employed to investigate two sets of Ti1-xAlxN thin films deposited by magnetron reactive sputtering from two types of metallic targets onto Si (100). Lattice symmetry of crystallised domains and columnar growth structure of the films are characterized by X-ray diffraction (XRD) and electron microscopy (TEM, HRTEM). Several local probes such as X-ray absorption fine structure (XAFS), diffraction anomalous fine structure (DAFS) and Electron Energy Loss Spectroscopies (EELS) which are very sensitive to the symmetry of the atomic sites either octahedral for fcc lattice or tetrahedral for hcp one are carried out. For Ti-rich films (x < 0.5), the competitive growth of cubic domains between [200]c and [111]c is observed. For Al-rich films (x > 0.7) have a domain growth well crystallized in the direction [002]h the hexagonal lattice. In addition, the cubic / hexagonal transition in Al contents higher is observed for films from sintered target. These films show better wear resistance than those deposited from target compartmentalized.

Semi conductors are of technological importance and attracted many of the re-searchers. ZnO belongs to the family of II-VI semiconductors and has material properties well suitable to UV light emitters, varistors, Schottky diodes, gas sensors, spintronics, ferroelectric devices and thin film transistors. It has been considered as a competitor to GaN, which belongs to the family of III-V semiconductors. This is due to the fact that ZnO of high quality can be deposited at lower growth temperatures than GaN, leading to the possibility of transparent junctions on less expensive substrates such as glass. This will lead to low-cost UV lasers with important applications in high-density data storage systems etc. One of the most popular growth techniques of ZnO is physical sputtering. As compared to sol-gel and chemical-vapor deposition, the magnetron sputtering is a preferred method because of its simplicity and low operating temperatures. Hence, detailed investigations were carried out on undoped and doped ZnO thin films primarily deposited by magnetron sputtering. The obtained results in the present work are presented in the form of a thesis. Chapter 1: A brief discussion on the crystal structure of ZnO material and its possible applications in the different areas such as Schottky diodes, spintronics, ferroelectric devices and thin film transistors are presented. Chapter 2: This chapter deals with various deposition techniques used in the present study. It includes the magnetron sputtering, thermal oxidation, pulsed-laser ablation and sol-gel technique. The experimental set up details and the deposition procedures are described in detail i.e., the deposition principle and the parameters that will affect the film properties. A brief note on the structural characterization equipments namely, X-ray diffraction, scanning electron microscopy, atomic force microscopy, transmission electron microscopy and the optical characterization equipments namely, transmission spectroscopy is presented. The transport properties of the films were studied which include Dielectric studies, impedance studies, device characterization and are discussed. Chapter 3: The optimization of ZnO thin films for Schottky diode formation and The characterization of various Schottky diodes is presented in this chapter. P-type conductivity in ZnO was implemented by the variation of partial pressure of oxygen during the sputtering and are discussed. A method to achieve low series resistance hetero-junction was achieved using thermal oxidation method and the detailed transport properties were studied. The optical investigation carried out on the ZnO thin films under various growth conditions are also presented. Chapter 4: This chapter deals with the processing, structural, electrical, optical and magnetic properties of Mn doped ZnO thin films grown by pulsed laser ablation. Structural investigations have shown that the Mn incorporation increases the c-axis length due to the relatively larger ionic size of the Mn ions. Studies conducted both at low and high concentration region of Zn1¡xMnxO thin films showed that the films are anti-ferromagnetic in nature. The transport measurements revealed that the electrical conductivity is dominated by the presence of shallow traps. Optical investigations suggested the absence of midgap absorption and confirm the uniform distribution of Mn in wurtzite structure. Chapter 5: Carrier induced ferromagnetism in Co doped ZnO thin films were studied and the results are presented in this chapter. High density targets were prepared by solid state reaction process and the thin films were deposited by pulsed laser ablation technique. Two compositions were studied and it was found that with increase in substrate temperature, c-axis length decreases. Optical studies suggested a strong mid gap absorption around 2eV and could be attributed to the d-d transitions of tetrahedral coordinated Co2+. The presence of ferromagnetism in these films makes them potential candidates for spintronics applications. Chapter 6: It has been reported in literature that o®-centered polarization will drive ferroelectric phase transition. Motivated by such results, substitution of Lithium in ZnO was studied in detail. The structural and electrical properties were investigated over a wide range of composition (0-25%). The ferroelectric studies were carried out both in metal-insulator-metal (MIM) and metal-insulator-semiconductor (MIS) configuration and are presented in this chapter. The appearance of Ferro electricity in these films makes them potential candidates for ferroelectric memory devices. Chapter 7: This chapter describes the studies conducted on Mg doped ZnO Thin films grown by multi-magnetron sputtering. The hexagonal phases of the films were evaluated. All the films exhibited c-axis preferred orientation towards (002) orientation. Micro structural evolutions of the films were carried out through scanning electron microscopy and atomic force microscopy. Ferroelectric properties were investigated in both metal-insulator-metal (MIM) and metal-insulator-semiconductor (MIS) configurations. It was observed that the Mg concentration increases the band gap and the details on optical investigations are also presented in this chapter. Chapter 8: ZnO based thin film transistors have been fabricated and characterized using ZnO as active channel layer and Mg doped ZnO as dielectric layer. Excellent leakage properties of the gate dielectric were studied and presented in this chapter. These studies demonstrated that Mg doped ZnO thin films are suitable candidates for gate dielectric applications. Conclusions: This section presents the conclusions derived out of the present work. It also includes a few suggestions on future work on this material.

Το θέμα αυτής της διπλωματικής εργασίας είναι η παρασκευή με τη μέθοδο sputtering και ο χαρακτηρισμός μαγνητικών λεπτών υμενίων. Στo πρώτο κεφάλαιο, που αποτελεί και την εισαγωγή, γίνεται μια αναφορά στη τεχνολογία των λεπτών υμενίων και δίνεται το στοιχειώδες θεωρητικό υπόβαθρο των τεχνικών ανάπτυξης αυτών. Στο δεύτερο κεφάλαιο παρουσιάζεται η διάταξη sputtering που χρησιμοποιήθηκε για την ανάπτυξη των μαγνητικών υμενίων και δίνονται τα αποτελέσματα της βαθμονόμησης ενός μετρητικού πάχους υψηλής ακρίβειας. Το τρίτο κεφάλαιο αναφέρεται στην κατασκευή και πιστοποίηση μιας πλήρως αυτοματοποιημένης και χαμηλού κόστους διάταξης μέτρησης μαγνητικών βρόχων μέσω του φαινομένου Kerr, με μέγιστο πεδίο πόλωσης 2Τ. Το τέταρτο κεφάλαιο αναφέρεται στις πειραματικές λεπτομέρειες της παρασκευής των μαγνητικών λεπτών υμενίων Νικελίου και Κοβαλτίου και δίνονται τα αποτελέσματα του δομικού και μαγνητικού χαρακτηρισμού τους. Τέλος, στο πέμπτο κεφάλαιο, παρουσιάζονται τα συμπεράσματα και οι παρατηρήσεις που προέκυψαν κατά τη διάρκεια της ενασχόλησης με τη διπλωματική εργασία. Γίνονται, επιπλέον, και ορισμένες προτάσεις για τη μελλοντική εξέλιξη των συστημάτων sputtering και ΜΟΚΕ, ενώ τονίζεται και το τεχνολογικό ενδιαφέρον που παρουσιάζουν τα υμένια που παρασκευάσθηκαν. / The subject of this diploma thesis is the growth using the sputtering process and the characterization of thin magnetic films. The first chapter refers to thin films' technology and there is given the elementary theoretical background of the thin films’ growth. In the second chapter, there is presented the sputtering device, which is used for the growth of the magnetic films. Also, there is given the results of the calibration of a newly established thickness monitor, which is used for high accuracy thickness measurements. In the third chapter, there is given the description of the construction of a fully automatic and low cost magneto - optic Kerr effect magnetometer for the magnetic loops' measurement in a maximum magnetic field of 2T. There are, also, given the magnetic loops which are used for the construction’s certification. The fourth chapter refers to the experimental details about the preparation of the Nickel and Cobalt magnetic thin films. There are, also, given the results about the structural and magnetic characterization of the thin films. Finally, in the fifth chapter, there are presented the conclusions and the observations, which arose during the diploma thesis. There are, also, presented some proposals about the future progress of the sputtering and MOKE systems, whereas at the same, there is stressed the technical interest of the thin films, which are prepared.

Dünne Schichten aus hydrogenisiertem amorphem Silizium a-Si:H spielen für die Photovoltaik eine wichtige Rolle. Einerseits kommt für die Dünnschicht-Photovoltaik unterschiedlich dotiertes a-Si:H in den Schichten einer p-i-n-Solarzelle zur Anwendung, andererseits stellen Heterokontakt-Solarzellen aus amorphem und kristallinem Silizium (a-Si:H/c-Si) wegen ihres hohen Wirkungsgrades derzeit ein sehr aktuelles Forschungsthema dar. Die Abscheidung der a-Si:H-Schichten im Rahmen dieser Arbeit erfolgt mit der Methode des Magnetronsputterns (Kathodenzerstäubung). Dieses für die in-line-Beschichtung etablierte Verfahren wird speziell für die Photovoltaik noch nicht in industriellem Maßstab eingesetzt (lediglich für transparente leitfähige Oxide TCO). Insbesondere existiert nur eine geringe Zahl von Veröffentlichungen zu Heterokontakten, welche mittels Magnetronsputtern hergestellt wurden. Ein Schwerpunkt der vorliegenden Arbeit ist daher die Herstellung sowie Charakterisierung solcher Heterokontakte unter dem Aspekt variierter Abscheide- und Prozessparameter (Substrattemperatur, Wasserstoffflussrate, Ionenbeschuss). Das für das Sputtern erforderliche Plasma wird mit einer im Mittelfrequenzbereich gepulsten Gleichspannung angeregt. Ein dadurch mehr oder weniger ausgeprägter Ionenbeschuss der wachsenden Schichten in Abhängigkeit der Pulsparameter wird hier analysiert. Die Charakterisierung der Heterokontakte erfolgt hauptsächlich anhand deren Strom-Spannung-Kennlinien, welche auch bei variierter Temperatur gemessen werden. Erzielte Gleichrichtungsverhältnisse um 10000:1 sowie Diodenidealitätsfaktoren η ≈ 1,3 kennzeichnen (p)a-Si:H/(n)c-Si-Heterokontakte mit den besten halbleiterphysikalischen Eigenschaften. Bei zu schwacher Schichthydrogenisierung wurde ein Ladungstransportmechanismus nachgewiesen, welcher in der Literatur als multi-tunneling capture-emission MTCE bekannt ist. Eine erhöhte Hydrogenisierung unterdrückt diesen Mechanismus nahezu vollständig. Durch Abscheidung unterschiedlich stark bordotierter a-Si:H-Schichten wird außerdem die Dotiereffizienz beurteilt. Hohe Werte sind bei amorphen Halbleitern im Allgemeinen schwer zu erreichen. Die mit stärkerer Dotierung erhöhte Gleichrichterwirkung lieferte hier ein Indiz für eine nachweisbare Dotiereffizienz.

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.

Ce travail porte sur la compréhension des mécanismes de nucléation-croissance et le développement de contraintes associé lors du dépôt par pulvérisation de films minces métalliques. Le développement d’un dispositif de mesure in-situ en cours de croissance de la résistivité électrique est présenté et les potentialités offertes par son couplage avec deux autres diagnostics in-situ : la mesure de courbure du substrat et la spectroscopie différentielle de surface, ainsi qu’avec des caractérisations structurales, morphologiques et chimiques ex-situ (DRX, XRR, METHR, EELS, AFM) ont permis de mettre en évidence : le rôle clé joué par la température homologue et la structure d’équilibre du matériau déposé pour guider le mode de croissance 2D ou 3D et les contraintes associées. Pour les métaux à croissance 3D étudiés (Ag, Au, Pd et Ir) tous de structure CC, nous avons montré que l’amplitude du pic de tension associée au stade de coalescence était liée à la mobilité atomique des adatomes ; son maximum correspondant à la continuité du film. Nous avons montré que l’épaisseur de coalescence et donc la microstructure et la contrainte des éléments de forte mobilité pouvaient être contrôlées par la présence d’un surfactant en cours de croissance. Il est exposé que pour les métaux de faible mobilité atomique (Mo, W, Ta, Fe) et/ou de structure CC, la croissance débute par la stabilisation d’une amorphe suivie par la cristallisation vers la phase d’équilibre CC (Mo, Fe) ou la structure quadratique dans le cas du Ta, induite par la minimisation des énergies de surface/interface. Les premiers stades de croissance complexes du système Pd/Si liés à une forte réactivité d’interface ont été expliqués par la formation d’un siliciure d’interface tout d’abord amorphe qui cristallise, lorsque l’épaisseur de Pd déposée devient suffisante, par ségrégation dynamique du Si dans le métal. La très forte dissymétrie des interfaces Pd/Si et Si/Pd ainsi que le rôle de la température et du réservoir de Si sur la formation du siliciure ont été étudiés. Les interdépendances entre contrainte de croissance en régime stationnaire, microstructure, énergie déposée et cinétique de croissance dans le cas de métaux de faible mobilité ont été élucidées et le rôle majeur des joints de grains et des puits de surface sur la relaxation des défauts de types interstitiels en excès induits lors de dépôts énergétiques démontré. Une extension aux dépôts énergétiques du modèle cinétique de Chason de développement des contraintes est proposée. / Size reduction for the race towards nanoscale devices impacts physical properties of materials due to morphology, microstructure, defects and presence of surfaces and interfaces, but also makes challenging their structural characterizations. Moreover, thin film growth by physical vapor deposition is a non-equilibrium process involving dynamics effects, which inherently affects nanostructure formation. Thanks to the development and use of in situ and real-time diagnostics, easily implementable in a vacuum chamber, as those based on the wafer curvature measurement, electrical resistivity or also the surface reflectance spectroscopy, described in this work, we are able to address these issues. An original 4 points probe resistivity setup, in situ and real-time, in a magnetron chamber, has been developed for this study, allowing samples introduction by a load-lock system and the growth of homogeneous, dense metallic films. Potentialities of these techniques are highlighted by studying magnetron sputtered metallic systems with various atomic mobility and interfacial reactivity. The sensibility of these techniques, at the sub monolayer scale, allows a better understanding of the firsts growth stages, nucleation processes, phase transformations and defects incorporation. Influence of microstructure (grain size), kinetics (growth rate) and deposited energy has been systematically studied. The main results obtained revealed: a correlation between the magnitude of tensile stress associated with the coalescence stage and the atomic mobility of adatoms during Volmer-Weber growth of Ag, Au, Pd and Ir thin films on a-SiOx; a two dimensional growth mode for films of lower mobility (Fe, Mo, Ta) on a-Si, with the stabilization of an amorphous layer before the crystallization of the equilibrium bcc structure (Fe and Mo) or the metastable tetragonal structure in the case of Ta, driven by the minimization of surface/interface energies; the strong reactivity of Pd films sputtered on Si or Ge (amorphous or crystalline) substrates, leading to the room-temperature formation of a crystalline silicide (germanide) Pd2Si (or Pd2Ge) phase whose crystallographic orientation depends on the nature of the sublayer and where the silicon is the fast diffuser; the complementary roles of surface and grain boundaries on the steady-state compressive stress regime observed under energetic conditions of growth (10-100eV). To account for these observations, an extension of Chason’s theoretical model is presented.