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Revestimentos finos de carboneto de nióbio (NbC) puro e dopados com níquel (Ni) foram obtidos mediante a técnica de deposição reativa por magnetron sputtering, utilizando metano (CH4) como fonte de carbono (C). O filme de NbC usado como referência foi depositado aplicando uma potência de 2500 W ao alvo de Nb e, os revestimentos de NbxNiyCz foram depositados diminuindo a potência aplicada ao alvo de Nb e aumentando a potência aplicada ao alvo de Nb-Ni, dando origem à seis revestimentos com teores de Ni crescentes. As caracterizações microestrutural e estrutural dos revestimentos de NbC e NbxCyNiz foram realizadas por meio das técnicas de difração de raios-X (DRX), Espectroscopia Fotoeletrônica de Raios X (XPS), Espectroscopia Raman, Microscopia Eletrônica de Transmissão (MET) e Microscopia Eletrônica de Varredura (MEV). As propriedades mecânicas dos revestimentos foram estudas mediante a técnica de nanoindentação instrumentada, com o intuito de avaliar a dureza (H) e o módulo de elasticidade (E). A adesão dos revestimentos ao substrato foi avaliada usando ensaios Rockwell C e esclerometria linear instrumentada. A estabilidade térmica dos revestimentos foi realizada em forno com atmosfera controlada em temperaturas de 600 °C e 800 °C por 2h. Finalmente, a resistência à oxidação dos revestimentos foi estudada por meio de ensaios de Termogravimetria (TGA - \"Thermogravimetric Analysis\") de aquecimento contínuo e isotérmicos. Os resultados de adesão obtidos mostraram boa aderência (modo de falha HF1) dos filmes de NbC e NbxNiyCz ao substrato de aço AISI M2, nas condições como recém depositado e revenido a 600 °C, indicando que a deposição do gradiente de intercamadas de Cr, CrC e do gradiente CrC / NbC foi efetiva evitando falhas adesivas. A adição de Ni na estrutura dos revestimentos de NbC promoveu a formação de estruturas nanocompósitas, composta de nanocristalitos de NbC e NiCx. Adicionalmente, a introdução de níquel causou um aumento na dureza nos revestimentos como recém depositados, aumentando de 17 para 25 GPa para teores de Ni de 0 para 13 at. %, respectivamente, e, na resistência à oxidação sobre o revestimento puro de NbC, de 380 °C para 480 °C nos revestimentos com níquel. Finalmente, as análises de estabilidade térmica permitiram observar que os precipitados de NiCx se decompõem durante os tratamentos de recozimento a 600 e 800 °C, o que promoveu um aumento nos valores de dureza e módulo de Young para todos os revestimentos, atribuído ao aumento da cristalinidade dos revestimentos. / Niobium carbide (NbC) coatings doped with Nickel (Ni) were deposited by reactive DC - magnetron sputtering using methane (CH4) as carbon (C) source. Reference NbC coating was deposited with a total power of 2500 W and NbxNiyCz coatings were deposited by decreasing the power applied to the Nb target and increasing the power applied to the Nb-Ni target, giving rise to coatings with increasing Ni content. Structural and microstructural characterizations of NbC and NbxNiyCz coatings were performed using X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Raman Spectroscopy, Transmission Electron Microscopy (MET) and Scanning Electron Microscopy (MEV). Mechanical properties of the coatings were studied using the instrumented nanoindentation technique, in order to evaluate the Hardness (H) and Elastic modulus (E). The adhesion between coatings and substrate was evaluated using Rockwell C test and instrumented linear scratch tests. The tests for studying the thermal stability of the coatings were carried out in a controlled atmosphere chamber furnace at temperatures of 600 °C and 800 °C for 2h. Finally, the oxidation resistance of the coatings was studied by means of Thermogravimetric Analysis (TGA) tests of continuous and isothermal heating. The NbC and NbxNiyCz films in the as-deposited condition and annealed at 600 °C, showed good adhesion (failure mode HF1) to the AISI M2 steel substrate, indicating that the adhesion interlayer of the Cr, CrC and a gradient CrC/NbC layer was effective in avoiding adhesive failures. The increasing of Ni content in the structure of NbC coatings promoted the formation of nanocomposite structures, composed of a mixture of NbC and NiCx nanocrystallites. Additionally, the introduction of nickel allows increasing the hardness for the coatings in the as-deposited condition, from 17 to 25 GPa for Ni contents from 0 to 13 at. %, respectively, and, improving the oxidation resistance over the pure NbC coating, from 380 °C to 480 °C for the Ni-rich coatings. Finally, the thermal stability analyses showed that the NiCx precipitate decompose during the annealing treatments at 600 °C and 800 °C, which promoted an increase in the hardness and Young\'s modulus values for all coatings. These behaviors were attributed to the increase of crystallinity of the coatings.

Union between top-down and bottom-up assembly is inevitable when scaling down physical, chemical, and biological sensors and probes. Current sensor/probe-based technologies are firmly founded on top-down manufacturing, with limitations in cost of production, manufacturing methods, and material constraints. As an alternative to such limitations, contemporary synthesis techniques for one-dimensional nanostructures have been combined with established methods of micro-fabrication for the development of novel tools and techniques for nanotechnology. More specifically, this dissertation is a systematic study of the synthesis and characterization of ZnO nanostructures for piezoelectric applications. Within this study the following goals have been achieved: 1) rational design and control of a diversity of novel ZnO nanostructures, 2) improved understanding of polar-surface-dominated (PSD) phenomena among Wurtzite crystal structures, 3) confirmation of Taskers Rule via the synthesis, characterization, and modeling of polar-surface-dominated nanostructures, 4) measurement of the surface-charge density for real polar surfaces of ZnO, 5) confirmation of the electrostatic polar-charge model used to describe polar-surface-dominated phenomena, 6) dispersion of ZnO nanobelts onto the selective layers of surface acoustic wave (SAW) devices for gas sensing applications, 7) manipulation of ZnO nanostructures using an atomic force microscope (AFM) for the development of piezoelectric devices, 8) fabrication of bulk acoustic resonator (BAR) and film bulk acoustic resonator (FBAR) devices based on the integrity of individual ZnO belts, 9) electrical characterization of a ZnO belt BAR device, 10) prediction and confirmation of the electrical response from a BAR device using a one-dimensional Krimholt-Leedom-Matthaei (KLM) model, and 11) development of a finite element model (FEM) to accurately predict the electrical response from ZnO belt BAR and FBAR devices in 3D.

Boron nitride is found mainly in two crystal structures / in hexagonal structure (h-BN) which is very much like graphite and in cubic structure (c-BN) with properties very close to those of diamond. h-BN is a natural lubricant due to its layered structure. It is generally used in sliding parts of the moving elements such as rotating element beds in turbine shafts. Since c-BN is the hardest known material after diamond it is used in making hard metal covers. In addition to its possible microelectronics applications (can be used to make p-n junction), its resistance to high temperatures and its high forbidden energy gap are its superiorities over diamond. Recent studies have shown that c-BN can be produced by Physical Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD) in plasma. But these studies have failed to determine how all of the production parameters (boron and nitrogen sources, composition of the gas used, substrate, RF power, bias voltage, substrate temperature) affect the c-BN content, mechanical stress and the deposition rate of the product with a systematic approach. The systematic study was realized in the range of available experimental ability of the present PVD and CVD equipment and accessories. The BN films were produced in the plasma equipment for CVD using RF and MW and magnetron sputtering and were studied with the measurement and testing facilities. It is believed that with this approach it will be possible to collect enough experimental data to optimize production conditions of BN with desired mechanical and optoelectronic properties. h-BN films were successfully deposited in both systems. It was possible to deposit c-BN films with the MW power, however they were weak in cubic content. Deposition at low pressures eliminated the hydrogen contamination of the films. High substrate temperatures led to more chemically and mechanically stable films.

With the aim to gain a deeper understanding of the role of the angle of incidence in physical vapor deposition, experimental, and computer-based studies were conducted. Electron beam evaporation and ion beam sputtering were used as deposition methods. The materials germanium, silicon, and molybdenum were deposited at different incidence angle, different temperatures and varied residual gas atmospheres. Established models could not be used to adequately explain the obtained relations between morphological parameters, as the tilt angle, with the incidence angle. To investigate the interplay of self-shadowing and competitive growth, an on-lattice simulation was developed. Care was taken to avoid any artificial anisotropy. Comparison with an, additionally developed, off-lattice simulation was used to verify this. Based on the made observations, an analytical model was deduced that combines the material properties and the deposition conditions into a single parameter. The predictions of this model were verified for the experimental observations, the results of the computer simulations, and on literature data. In the last part of the thesis, methods are shown that facilitate to modify the properties of the obliquely deposited thin films to fit requirements of various applications. This includes in situ doping of silicon nanostructures, creation of core-shell structures, as well as biochemical surface functionalization of silver nanostructures. On the example of the latter, various bio-sensing applications are presented.:1 MOTIVATION 7 2 BASIC CONCEPTS 9 2.1 Physical vapor deposition (PVD) 9 2.2 Deposition at oblique angles 14 2.3 Controlling the thin film morphology 16 3 EXPERIMENTAL METHODS 19 3.1 Sample preparation 19 3.2 Characterization techniques 32 4 EXPERIMENTAL RESULTS 37 4.1 Columnar structure and evolutionary selection 37 4.2 Tilt angles and density 42 4.3 Fan angles 45 4.4 Relevance of beam divergence 47 4.5 Summary 50 5 SIMULATION 53 5.1 Introduction 53 5.2 Off-lattice approach 54 5.3 On-lattice approach 59 5.4 Further applications of the on-lattice simulation 64 5.5 Other aspects 72 5.6 Summary 76 6 OBLIQUE ANGLE DEPOSITION MODEL 77 6.1 Semi-Empirical models 77 6.2 Tanto’s fan model 78 6.3 Development of the Competition Model 80 6.4 Verification of the model 84 6.5 Summary 89 7 FILM OPTIMIZATION FOR APPLICATIONS 91 7.1 Boron doped Si nanostructures 91 7.2 Surface functionalization for biosensors 95 7.3 Core-shell structures by pulsed electrodeposition 101 7.4 Summary 105 8 SUMMARY 107 9 BIBLIOGRAPHY 109 10 LIST OF ABBREVIATIONS 121 11 ACKNOWLEDGEMENTS 123 APPENDIX 125 PUBLICATION LIST 131 SELBSTSTÄNDIGKEITSERKLÄRUNG 133 / Mit dem Ziel ein besseres Verständnis des Einflusses des Einfallswinkels in der physikalischen Gasphasenabscheidung zu erreichen, wurden experimentell realisierte und am Computer simulierte Dünnschichten untersucht. Als Abscheidetechniken kamen sowohl Elektronenstrahl-Verdampfen als auch Ionenstrahl-Zerstäubung zum Einsatz. Es wurden die Materialien Germanium, Silicium und Molybdän verwendet, die bei verschiedenen Einfallswinkeln, verschiedenen Substrattemperaturen und variiertem Restgas abgeschieden wurden. Die beobachteten Zusammenhänge, von bspw. kolumnarer Verkippung und Einfallswinkel, konnten nicht mit den etablierten Modellen in Einklang gebracht werden. Um das genaue Zusammenspiel von Abschattung und Konkurrenz-Wachstum zu verstehen, wurde eine „on-lattice“ Computersimulation entwickelt, mit dem besonderen Augenmerk auf die Vermeidung von gitterbasierten Anisotropien. Dies wurde durch Vergleich mit einer, ebenfalls entwickelten, „off-lattice“ Simulation sichergestellt. Ausgehend von den beobachteten Effekten konnte ein analytisches Modell entwickelt werden, welches die Materialeigenschaften und Abscheidebedingungen in einen einzigen Parameter vereint. Die Vorhersagen des Modells wurden an den hergestellten Schichten, den Computersimulationen und an Literaturdaten verifiziert. Abschließend werden Methoden aufgezeigt, die schräg abgeschiedenen nanostrukturierten Schichten verschiedenen Anwendungen anzupassen. Dies umfasst die in situ Dotierung von Siliciumnanostrukturen, die Erzeugung von Kern-Schale-Strukturen, sowie die biochemische Oberflächenfunktionalisierung von Silbernanostrukturen. Am Beispiel der letztgenannten werden verschiedene Anwendungen in der Biosensorik detaillierter vorgestellt.:1 MOTIVATION 7 2 BASIC CONCEPTS 9 2.1 Physical vapor deposition (PVD) 9 2.2 Deposition at oblique angles 14 2.3 Controlling the thin film morphology 16 3 EXPERIMENTAL METHODS 19 3.1 Sample preparation 19 3.2 Characterization techniques 32 4 EXPERIMENTAL RESULTS 37 4.1 Columnar structure and evolutionary selection 37 4.2 Tilt angles and density 42 4.3 Fan angles 45 4.4 Relevance of beam divergence 47 4.5 Summary 50 5 SIMULATION 53 5.1 Introduction 53 5.2 Off-lattice approach 54 5.3 On-lattice approach 59 5.4 Further applications of the on-lattice simulation 64 5.5 Other aspects 72 5.6 Summary 76 6 OBLIQUE ANGLE DEPOSITION MODEL 77 6.1 Semi-Empirical models 77 6.2 Tanto’s fan model 78 6.3 Development of the Competition Model 80 6.4 Verification of the model 84 6.5 Summary 89 7 FILM OPTIMIZATION FOR APPLICATIONS 91 7.1 Boron doped Si nanostructures 91 7.2 Surface functionalization for biosensors 95 7.3 Core-shell structures by pulsed electrodeposition 101 7.4 Summary 105 8 SUMMARY 107 9 BIBLIOGRAPHY 109 10 LIST OF ABBREVIATIONS 121 11 ACKNOWLEDGEMENTS 123 APPENDIX 125 PUBLICATION LIST 131 SELBSTSTÄNDIGKEITSERKLÄRUNG 133

Indiana University-Purdue University Indianapolis (IUPUI) / Thermal barrier coatings (TBCs) have been extensively employed as thermal protection in hot sections of gas turbines in aerospace and power generation applications. However, the fabrication of TBCs still needs to improve for better coating quality, such as achieving coating thickness' uniformity. However, several previous studies on the coating thickness prediction and a systematic understanding of the thickness evolution during the deposition process are still missing. This study aims to develop high-fidelity computational models to predict the coating thickness on complex-shaped components. In this work, two types of models, i.e., ray-tracing based and heat transfer based, are developed. For the ray-tracing model, assuming a line-of-sight coating process and considering the shadow effect, validation studies of coating thickness predictions on different shapes, including plate, disc, cylinder, and three-pin components. For the heat transfer model, a heat source following the Gaussian distribution is applied. It has the analogy of the governing equations of the ray-tracing method, thus generating a temperature distribution similar to the ray intensity distribution in the ray-tracing method, with the advantages of high computational efficiency. Then, using a calibrated conversion process, the ray intensity or the temperature profile are converted to the corresponding coating thickness. After validation studies, both models are applied to simulate the coating thickness in a rotary turbine blade. The results show that the simulated validation cases are in good agreement with either the experimental, analytical, or modeling results in the literature. The turbine blade case shows the coating thickness distributions based on rotating speed and deposition time. In summary, the models can simulate the coating thickness in rotary complex-shaped parts, which can be used to design and optimize the coating deposition process.

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A detailed understanding of failure mechanisms in thermal barrier coatings (TBCs) can help develop reliable and durable TBCs for advanced gas turbine engines. One of the characteristics of failure in electron beam physical vapor deposited (EB-PVD) TBCs is the development of instability, named rumpling, at the interface between (Ni, Pt)Al bond coat and thermally grown oxide (TGO). In this study, thermal cycling at 1100°C with 1 hr dwell time was carried out on 25.4mm disc specimens of TBCs that consisted of EB-PVD coated ZrO2-7wt. %Y2O3, (Pt,Ni)Al bond coat, and CMSX-4 Ni-based superalloy. At specific fraction of lifetime, TBCs were examined by electron microscopy and photostimulated luminescence (PL). Changes in the average compressive residual stress of the TGO determined by PL and the magnitude of rumpling, determined by tortuosity from quantitative microstructural analyses, were examined with respect to the furnace thermal cyclic lifetime and microstructural evolution of TBCs. The combination of elastic strain energy within the TGO and interfacial energy at the interface between the TGO and the bond coat was defined as the TGO energy, and its variation with cyclic oxidation time was found to remain approximately constant ~135J/m2 during thermal cycling from 10% to 80% thermal cyclic lifetime. Parametric study at ~135J/m2 was performed and variation in residual stress with rumpling for different oxide scale thicknesses was examined. This study showed that the contribution of rumpling in residual stress relaxation decreased with an increase in TGO thickness. High pressure turbine blades serviced for 2843 hours and in the as coated form were also examined using electron microscopy and photostimulated luminescence. The difference in iv residual stress values obtained using PL on the suction and pressure sides of as-coated turbine blade were discussed. The presence of a thick layer of deposit on the serviced blade gave signals from stress free α-Al2O3 in the deposit, not from the TGO. The TGO growth constant data from the disc-shape TBCs, thermally cycled at 1100°C, and studies by other authors at different temperatures but on similar EB-PVD coated TBCs with (Pt, Ni)Al bond coat and CMSX-4 Nibased superalloy were used to determine the temperature profile at the YSZ/bond coat interface. The interfacial temperature profiles of the serviced blade and the YSZ thickness profile were compared to document the variable temperature exposure at the leading edge, trailing edge, suction and the pressure side.

This dissertation tested the hypothesis that energy transferred from a plasma or plume can be used to optimize the structure, chemistry, topography, optical and electrical properties of pulsed laser deposited and sputtered thin-films of ZnO, a-BOxNy, and few layer 2H-WS2 for transparent electronics devices fabricated without substrate heating or with low substrate heating. Thus, the approach would be compatible with low-temperature, flexible/bendable substrates. Proof of this concept was demonstrated by first optimizing the processing-structure-properties correlations then showing switching from accumulation to inversion in ITO/a-BOxNy/ZnO and ITO/a-BOxNy/2H-WS2 transparent MIS capacitors fabricated using the stated processes. The growth processes involved the optimization of the individual materials followed by growing the multilayer stacks to form MIS structures. ZnO was selected because of its wide bandgap that is transparent over the visible range, WS2 was selected because in few-layer form it is transparent, and a-BOxNy was used as the gate insulator because of its reported atomic smoothness and low dangling bond concentration. The measured semiconductor-insulator interfacial trap properties fall in the range reported in the literature for SiO2/Si MOS structures. X-ray photoelectron spectroscopy (XPS), Hall, photoluminescence, UV-Vis absorption, and X-ray diffraction (XRD) measurements investigated the low-temperature synthesis of ZnO. All films are nanocrystalline with the (002) XRD planes becoming more prominent in films grown with lower RF power or higher pressure. Low power or high chamber pressure during RF magnetron sputtering resulted in a slower growth rate and lower energetic conditions at the substrate. Stoichiometry improved with RF power. The measurements show a decrease in carrier concentration from 6.9×1019 cm-3 to 1.4×1019 cm-3 as power increased from 40 W to 120 W, and an increase in carrier concentration from 2.6×1019 cm-3 to 8.6×1019 cm-3 as the deposition pressure increased from 3 to 9 mTorr. The data indicates that in the range of conditions used, bonding, stoichiometry, and film formation are governed by energy transfer from the plasma to the growing film. XPS characterizations, electrical measurements, and atomic force microscopy (AFM) measurements reveal an increase in oxygen concentration, improved dielectric breakdown, and improved surface topography in a-BOxNy films as deposition pressure increased. The maximum breakdown strength obtained was ~8 MVcm-1, which is comparable to a-BN. Metal-Insulator-Metal (MIM) structures of a-BOxNy grown at 10 and 15 mTorr suggest a combination of field-enhanced Schottky emission and Frenkel-Poole emission are likely transport mechanisms in a-BOxNy. In comparison, better fitted data was gotten for field enhanced Schottky emission which suggests the more dominant mechanism. The static dielectric constant range is 3.26 – 3.58 for 10 and 15 mTorr films. Spectroscopic ellipsometry and UV-Vis spectroscopy measured a bandgap of 3.9 eV for 15 mTorr grown a-BOxNy. 2H-WS2 films were grown on both quartz and a-BOxNy which revealed that the XRD (002) planes became more prominent as substrate temperature increased to 400 oC. AFM shows nano-grains at lower growth pressure. Increasing the growth pressure to 1 Torr resulted in the formation of larger particles. XPS chemical analysis reveals improved sulfur to tungsten ratios as pressure increased. Sulfur deficient films were n-type, whereas sulfur rich conditions produced p-type films. Frequency dependent C-V and G-V measurements revealed an interface trap concentration (Nit) of 7.3×1010 cm-2 and interface state density (Nss) of 7.5×1012 eV-1cm-2 for the transparent ITO/a-BOxNy/ZnO MIS structures, and approximately 2 V was required to switch the a-BOxNy/ZnO interface from accumulation to inversion. Using 2H-WS2 as the channel material, the ITO/a-BOxNy/2H-WS2 required approximately 4 V to switch from inversion to accumulation in both n and p-channel MIS structures. Interface trap concentrations (Nit) of 1.6×1012 cm-2 and 3.2×1010 cm-2, and interface state densities (Nss) of 1.6×1012 eV-1cm-2 and 6.5×1012 eV-1cm-2 were calculated for n and p-channel 2H-WS2 MIS structures, respectively. The data from these studies validate the hypothesis and demonstrate the potential of ZnO, a-BOxNy, and few layer 2H-WS2 for transparent electronics.

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