DC and RF magnetron co-sputtering techniques are one of the most suitable techniques in fabrication of thin films with different compositions. In this work, Al2O3 and Si/Al2O3 thin films were fabricated by using magnetron co-sputtering technique. For Al2O3 films, the stoichiometric, optical and crystallographic analyses were performed. For Si contained Al2O3 films, the formation conditions of Si nanocrystals were investigated. To do so, these thin films were sputtered on Si (100) substrates. Post annealing was done in order to clarify the evolution of Al2O3 matrix and Si nanocrystals at different temperatures. Crystallographic properties and size of the nanocrystals were investigated by X-ray diffraction (XRD) method. The variation of the atomic concentrations and bond formations were investigated with X-ray photoelectron spectroscopy (XPS). The luminescent behaviors of Si nanocrystals and Al2O3 matrix were investigated with photoluminescence (PL) spectroscopy. Finally, the characteristic emissions from the matrix and the nanocrystals were separately identified.

In this study, flash memory cells with high-k dielectric HfO2 as tunnel oxide and group IV (Si, Ge) nanocrystals were fabricated and tested. The device structure was grown by magnetron sputtering deposition method and analyzed by various diagnostic techniques such as X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy. The use of HfO2 tunnel oxide dielectric with high permittivity constant was one of the main purposes of this study. The ultimate aim was to investigate the use of Si and Ge nanocrystals together with HfO2 tunnel oxide in the memory elements. Interface structure of the fabricated devices was studied by XPS spectroscopy. A depth profile analysis was performed with XPS. Nanocrystal formations were verified using Raman spectroscopy technique. The final part of the study includes electrical characterization of memory devices fabricated using Si and Ge floating gate. C-V (Capacitance Voltage) and G-V (Conductance-Voltage) measurements and charge storage behaviour based on C-V measurements were performed. For comparison, structure of Si and Ge layers either in thin film or in the nanocrystal form were studied. A comparison of the C-V characteristics of these two structures revealed that the memory device with thin films do not confine charge carriers under the gate electrode as should be expected for a continuous film. On the other hand, the device with nanocrystals exhibited better memory behavior as a result of better confinement in the isolated nanocrystals. Trace amount of oxygen was found to be enough to oxidize Ge nanocrystals as confirmed by the Raman measurements. The charge storage capability is weakened in these samples as a result of Ge oxidation. In general, this work has demonstrated that high-k dielectric HfO2 and group IV nanocrystals can be used in the new generation MOS based memory elements. The operation of the memory elements are highly dependent on the material and device structures, which are determined by the process conditions.

<p>Quasicrystals is a new kind of material that have several interesting aspects to it. The unusual atomic structure entails many anomalous and unique physical properties, for example, high hardness, and extremely low electrical and thermal conductivity. In thin films quasicrystals would enable new functional materials with a combination of attractive properties.In this work, AlCuFe and Nanoflex steel, materials that are known to form quasicrystals in bulk, have been deposited as thin films on Si and Al2O3 substrates using DC magnetron sputtering. These thin films were heat treated, and the formation and growth of different phases, among other approximant and quasicrystalline phases, were studied using mainly in-situ X-ray diffraction.During the project several problems with the formation of quasicrystals were encountered, and it is proposed how to overcome these problems, or even how to make use of them. Finally, the quasicrystalline phase was realized, although it was not completely pure. In the end some suggestions for future work is presented.</p>

Investigations on pulsed reactive magnetron sputtering processes for the deposition of thin oxide films are presented by means of time-resolved and time-integrated measurements. The pulsed process can be successfully described in terms of a model of Berg et al. for reactive sputtering processes. Time-resolved Langmuir double probe measurements are confirmed using time-resolved optical emission spectroscopy. Combining the results leads to an insight into elementary processes governing the discharge. / Mit Hilfe zeitlaufgelöster und zeitlich mittelnder Methoden wird eine gepulste Magnetronentladung zur reaktiven Abscheidung von Oxidschichten untersucht. Das Modell von Berg et al. zur Beschreibung des Abscheideprozesses lässt sich dabei erfolgreich auf die reaktive Abscheidung mit einem gepulsten Prozess anwenden. Mittels zeitaufgelöster optischer Emissionsspektroskopie können die Ergebnisse zeitaufgelöster Langmuir-Doppelsondenmessungen bestätigt werden. In Kombination ermöglichen diese Verfahren die Untersuchung von Elementarprozessen in der Entladung.

Diese Dissertation befasst sich mit den Plasmaeigenschaften und dem Schichtbildungsprozess bei der Titanoxidbeschichtung mit dem reaktiven Puls-Magnetron-Sputterverfahren. Insbesondere werden die Vorgänge, die zu einer vermehrt oder vermindert starken Kristallinität und photokatalytischen Aktivität der Schichten führen, untersucht und die Verflechtungen mit den Beschichtungsbedingungen analysiert. Es werden Untersuchungen zur Messung der sich während der Beschichtung einstellenden Substrattemperatur, zur Messung des auf das Substrat einfallenden integralen Ionenstroms sowie zur Energieverteilung positiver und negativer Ionen vorgestellt. Zu den wichtigsten Erkenntnissen dieser Untersuchungen zählt, dass bei Nutzung des Pulspaket- bzw. des Bipolar-Pulsmodus bei Rechteck-Magnetrons eine um etwa Faktor zwei stärkere Substraterwärmung auftritt als bei Nutzung des Unipolar-Pulsmodus. Das ist auf einen höheren Ionenstrom auf das Substrat bei gleichzeitig höherer Selbstbiasspannung zurückzuführen, was insgesamt zu einem deutlich intensiveren Bombardement des Substrats mit Ionen führt. Durch Vergleich mit den Eigenschaften von DC-Plasmen konnte gezeigt werden, dass die unterschiedliche Lage der Anode relativ zum Magnetron-Magnetfeld die primäre Ursache für die gefundenen Unterschiede ist. Der Titanoxid-Beschichtungsprozess wurde umfassend untersucht und dabei die Abhängigkeiten der Kristallinität und der Schichteigenschaften von Substrattemperatur, Beschichtungsrate und von dem während der Beschichtung auftretenden Ionenbombardement aufgezeigt. Eine wichtiges Resultat ist, dass durch Anwendung eines intensiven Ionenbombardements des Beschichtungsplasmas die für kristallines Schichtwachstum erforderliche Substrattemperatur sinkt. Das wird durch Nutzung des Pulspaket- bzw. des Bipolar-Pulsmodus anstatt des Unipolar-Pulsmodus sowie durch Wahl eines reaktiveren Arbeitspunkts erreicht. Insgesamt konnte anhand der Untersuchungen der Parameterbereich, in dem die Abscheidung polykristalliner Titanoxidschichten möglich ist, in Richtung niedriger Substrattemperaturen und dünner Schichten ermittelt werden. / In this dissertation, the plasma characteristics and the layer forming process during the titanium oxide deposition with the reactive pulse magnetron sputtering method are investigated. In particular, the procedures which lead to a higher or lower crystallinity and photocatalytic activity are examined and the connections with the coating conditions are analyzed. Investigations are presented concerning the maximum substrate temperature during deposition, the integral ion current onto the substrate as well as the ion energy distribution function of positive and negative ions. One of the most important findings is that when using rectangular magnetrons in the pulse packet mode or in the bipolar pulse about to factor two stronger substrate heating arises in comparison to the unipolar pulse mode. That is due to a higher ion current onto the substrate and a higher self bias potential which leads altogether to a significantly higher ion bombardment of the substrate. It could be shown by comparison with the characteristics of DC plasmas that the different configuration of the anode relative to the magnetic field of the magnetrons is the primary cause for the differences. The titanium oxide coating process was comprehensively examined. Layer crystallinity and layer properties could be related to substrate temperature, deposition rate and ion bombardment during deposition. An important result is that by application of an intensive ion bombardment the substrate temperature necessary for crystalline layer growth decreases. This can be achieved by using the pulse packet or the bipolar pulse mode instead of the unipolar pulse mode as well as by choice of a more reactive working point. All in all, the parameter range in which is it possible to deposit polycrystalline titanium oxide layers could be determined toward low substrate temperatures and small layer thickness.

No description available.

In this thesis research on synthesis, microstructure and properties of carbide-based coatings is reported. These coatings are electrically conducting, and can be tailored for high hardness, low friction and wear, along with load-adaptive behaviour. Tailoring these properties is achieved by controlling the relative phase content of the material. Coatings have been synthesised by dc magnetron sputtering, and their structures have been characterised, mainly by X-ray photoelectron spectroscopy and X-ray diffraction. It has been shown that nanocomposites comprising of a nanocrystalline transition metal carbide (nc-MeCx, Me = Ti, Nb or V) and an amorphous carbon (a-C) matrix can result in low contact resistance in electrical contacts. Such materials also exhibit low friction and high resistance to wear, making them especially suitable for application in sliding contacts. The lowest contact resistance is attained for small amounts of the amorphous carbon phase. It has been shown that specific bonding structures are present in the interface between nc-TiCx and the a-C phases in the nanocomposite.  It was found in particular that Ti3d and C2p states are involved, and that considerable charge transfer occurs across the interface, thereby influencing the structure of the carbide. Further design possibilities were demonstrated for TiCx-based nanocomposites by alloying them with weakly carbide-forming metals, i.e., Me = Ni, Cu or Pt.  Metastable supersaturated solid solution carbides, (T1-xMex)Cy, were identified to result from this alloying process. The destabilisation of the TiCx-phase leads to changes in the phase distribution in the deposited nanocomposites, thus providing further control over the amount of carbon phase formed. Additional design possibilities became available through the decomposition of the metastable (Ti1-xMex)Cy phase through an appropriate choice of annealing conditions, yielding either more carbon phase or a new metallic phase involving Me. This alloying concept was also studied theoretically for all 3d transition metals using DFT techniques. It has also been demonstrated that Ar-ion etching (commonly used in the analysis of carbide based nanocomposites) can seriously influence the result of the analysis, especially for materials containing metastable phases. This implies that more sophisticated methods, or considerable care are needed in making these analyses, and that many of the earlier published results could well be in error.

<p>The fascinating optical properties of metallic nanostructures, dominated by collective oscillations of free electrons known as plasmons, open new opportunities for the development of devices fabrication based on noble metal nanoparticle composite materials. This thesis demonstrates a low-cost and versatile technique to produce stimuli-responsive ultrafast plasmonic nanostructures with reversible tunable optical properties. Albeit challenging, further control using thermal external stimuli to tune the local environment of gold nanoparticles embedded in VO2 host matrix would be ideal for the design of responsive functional nanocomposites. We prepared Au-VO2 nanocomposite thin films by the inverted cylindrical reactive magnetron sputtering (ICMS) known as hollow cathode magnetron sputtering for the first time and report the reversible tuning of surface plasmon resonance of Au nanoparticles by only adjusting the external temperature stimuli. The structural, morphological, interfacial analysis and optical properties of the optimized nanostructures have been studied. ICMS has been attracting much attention for its enclosed geometry and its ability to deposit on large area, uniform coating of smart nanocomposites at high deposition rate. Before achieving the aforementioned goals, a systematic study and optimization process of VO2 host matrix has been done by studying the influence of deposition parameters on the structural, morphological and optical switching properties of VO2 thin films. A reversible thermal tunability of the optical/dielectric constants of VO2 thin films by spectroscopic ellipsometry has been intensively also studied in order to bring more insights about the shift of the plasmon of gold nanoparticles imbedded in VO2 host matrix.</p>

De nombreuses applications modernes nécessitent l’utilisation de matériaux transparents dans le visible et le proche infrarouge. C’est le cas des vitrages pour le bâtiment, des vitres de voitures ou encore d’écrans de téléphone portable. La stratégie mise en place dans ces travaux de thèse est d’obtenir en surface d’un verre sodo-calcique, un matériau barrière aux propriétés similaires à la silice. Deux approches de traitements de surface visent à d’une part, modifier la chimie de surface par un traitement sous champ électrique assisté par voie thermique et d’obtenir une couche riche en SiO2 en surface. D’autre part, un revêtement est déposé sur le verre sodo-calcique, utilisé ici comme substrat. Ce dépôt se fait par pulvérisation cathodique magnétron et permettra de mettre en forme un matériau composite SiO2-TiO2 aux propriétés optiques de transparence et mécaniques de dureté optimisées et d’y associer des propriétés photocatalytiques performantes. / Many applications of the modern wolrd need transparent material especially in the visible range and near-IR. That is the case for windows for building or car, laptop screen. The purpose is to obtain a silica rich layer on the top of a soda-lime glass with similar properties to silica. Two ways have been defined. The first one is thermal poling treatment which consist in a thermal treatment electric field assisted to modify the surface chemistry and monitoring a silica rich layer on the top. The second way is to get a thin film by magnetron sputtering on the top of the soda-lime glass used here as substrate. A SiO2-TiO2 material is got with efficient optical properties of transparencey and mechanical properties (hardness). Photocatalytic activity have been demonstrated and provide self-cleaning properties.

Thin film cadmium telluride (CdTe) technology is the most important competitor for silicon (Si) based solar cells. Pulsed direct current (DC) magnetron sputtering is a new technique has been developed for thin film CdTe deposition. This technique is industrially scalable and provides uniform coating. It is also possible to deposit thin films at low substrate temperatures. A series of experiments are presented for the optimisation of the cadmium chloride (CdCl2) activation process. Thin film CdTe solar cells require CdCl2 activation process to improve conversion efficiencies. The role of this activation process is to increase the grain size by recrystallisation and to remove stacking faults. Compaan and Bohn [1] used the radio-frequency (RF) sputtering technique for CdTe solar cell deposition and they observed small blisters on CdTe layer surface. They reported that blistering occurred after the CdCl2 treatment during the annealing process. Moreover, void formation was observed in the CdTe layer after the CdCl2 activation process. Voids at the cadmium sulphide (CdS)/CdTe junction caused delamination hence quality of the junction is poor. This issue has been known for more than two decades but the mechanisms of the blister formation have not been understood. One reason may be the stress formation during CdTe solar cells deposition or during the CdCl2 treatment. Therefore, the stress analysis was performed to remove the defects observed after the CdCl2 treatment. This was followed by the rapid thermal annealing to isolate the CdCl2 effect by simply annealing. Small bubbles observed in the CdTe layer which is the first step of the blister formation. Using high resolution transmission electron microscopy (HR-TEM), it has been discovered that argon (Ar) working gas trapped during the deposition process diffuses in the lattice which merge and form the bubbles during the annealing process and grow agglomeration mainly at interfaces and grain boundaries (GBs). Blister and void formation were observed in the CdTe devices after the CdCl2 treatment. Therefore, krypton (Kr), neon (Ne) gases were used as the magnetron working gas during the deposition of CdTe layer. The results presented in this thesis indicated that blister and void formation were still existing with the use of Kr an Ne. Xe, which has a higher atomic mass than Kr, Ne, Ar, Cd and Te, was used as the magnetron working gas and it resulted in surface blister and void free devices.