Thin films of alumina were deposited on ferrite (NiₓZn₍₁₋ₓ₎Fe₂O₄), glass, single crystal silicon and graphite substrates by RF sputtering. Though standard, amorphous Al₂O₃ films are readily soluble in hot phosphoric acid, these sputtered films exhibited only reluctant etchability by the acid. Experiments were initially performed to understand the parameters in the sputtering process which were influential in the formation of unetchable films. The results showed that a high concentration of water vapor or oxygen molecules in the sputtering chamber during deposition was the most significant variable controlling the growth of unetchable films. The films were categorized according to their degree of solubility in H₃PO₄ and were examined using various microanalytical characterization techniques. TEM analysis directly showed the existence of crystalline γ-Al₂O₃ in the film at the film-substrate interface. The γ-Al₂O₃ phase grew with a preferred orientation coincident with the substrate orientation--as in heteroepitaxial growth. The occurrence of this film phase was related to the oxygen partial pressure, the substrate material, and the substrate temperature and was believed to be the cause of the film's incomplete etching behavior.

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The thesis has dealt with transparent conducting oxide (TCO) materials, with a focus on Al:ZnO and with studies on Sn:In2O3 and ZnO. TCOs are a material group that is used for its properties of being conductive and at the same time transparent. In solar cells, a top layer of TCO is often used to allow light to transmit into the cell and then conduct the resulting current.   A set of growth parameters was chosen and optimized through a literature study and experiments. The depositied thin films were characterized by optical and electrical characterization methods. Rf-magnetron-sputtering was used as the deposition method, where the influence of O2, argon and substrate temperature were the parameters to be studied. As a part of the characterization a model for spectroscopic ellipsometry on Al:ZnO was made, enabling faster measurement of transport properties. The main parameter affecting the TCO properties was found to be oxygen flow and the optimum flow value for each material has been determined. Substrate heating did not show any significant improvement on the resistivity of Al:ZnO with a minimum value of ~5.0*10-4 Ωcm while no heating resulted in a value of ~6.0*10-4  Ωcm. These values are comparable to the state-of-the-art from the literature.   As a demonstration of application, the developed AZO and ZnO were applied to CIGS solar cells and these were compared to a reference. The newly developed AZO and ZnO was comparable to the reference but a lower mean fill factor indicates that improvements can be made.

by Sou Ka Hou. / On t.p. "2', "3", and "T" are subscript following "deposition of" in the title. / Parallel title in Chinese characters. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1992. / Includes bibliographical references (leaves [88]). / Chapter 1. --- Introduction --- p.1 / Chapter 2. --- Computer-controlled sputtering system for deposition of high Tc thin films --- p.10 / Chapter 2.1 --- Introduction --- p.10 / Chapter 2.2 --- Vacuum system --- p.12 / Chapter 2.3 --- Gas flow control --- p.16 / Chapter 2.3.1 --- Design --- p.16 / Chapter 2.3.2 --- Flow control --- p.18 / Chapter 2.4 --- Gas pressure control --- p.21 / Chapter 2.4.1 --- Gauges --- p.21 / Chapter 2.4.2 --- Control method --- p.21 / Chapter 2.5 --- "Sputtering, guns and deposition control" --- p.24 / Chapter 2.5.1 --- Types --- p.24 / Chapter 2.5.2 --- Orientation of the sputter gun --- p.26 / Chapter 2.5.3 --- Dual magnetron gun system --- p.26 / Chapter 2.5.4 --- Deposition control system --- p.27 / Chapter 2.6 --- Substrate holder and temperature control --- p.30 / Chapter 2.6.1 --- Substrate holder --- p.30 / Chapter 2.6.2 --- Substrate temperature control --- p.31 / Chapter 2.7 --- Interlock protection --- p.34 / Chapter 2.8 --- Control program --- p.35 / Chapter 3. --- The presputtering effect --- p.39 / Chapter 3.1 --- Presputtering effect (a review) --- p.39 / Chapter 3.2 --- Emission spectroscopy on sputtered materials --- p.48 / Chapter 3.3 --- Experimental --- p.49 / Chapter 3.4 --- Emission spectra --- p.53 / Chapter 3.4.1 --- Effect of sputter power source --- p.53 / Chapter 3.4.2 --- Effect of gas ratio --- p.58 / Chapter 3.4.3 --- Effect of gas pressure --- p.64 / Chapter 3.4.4 --- Study of presputtering effect --- p.67 / Chapter 3.4.5 --- Monitoring the evaporation rate by the spectral line intensities --- p.71 / Chapter 4. --- Conclusion and discussion --- p.75 / Chapter Appendix A. --- Motor control --- p.77 / Chapter Appendix B. --- Thin film deposition --- p.82

Filmes finos de nitreto de silício com excesso de nitrogênio foram depositados sobre silício por sputtering reativo para obter estruturas emissoras de luz. As amostras foram modificadas por implantação iônica para verificar a influência dos dopantes arsênio (As) e boro (B) nos espectros de fotoluminescência (PL). As medidas de PL foram realizadas na faixa de temperatura entre 15-300 K e apresentaram uma emissão entre os comprimentos de onda 370-870 nm. Os dopantes introduziram uma emissão em 725 nm na banda de emissão, principalmente as dopadas com As. Foram realizadas medidas de microscopias para verificar a presença de nanoestruturas assim como a distribuição dos dopantes no material. As imagens de microscopias confirmaram a presença de nanocristais de nitreto de silício nas fases α, β e γ e identificaram a presença do dopante B nas fases cristalinas. O modelo de condução de Pool-Frenkel domina o transporte de portadores, indicando que a condução ocorre pelos níveis intrabandas, característica que definiu o modo que as recombinações radiativas ocorreram. As medidas de eletroluminescência (EL) apresentaram uma emissão centrada nos comprimentos de onda 760 e 880 nm (polarização negativa) e 1010 nm (polarização positiva) revelando diferenças significativas quando comparadas com as medidas de PL. Essa diferença esta associada à maneira como os elétrons populam os níveis intrabanda (excitação óptica para PL e elétrica para EL) que resulta em recombinações radiativas em diferentes comprimentos de ondas. A intensidade dos espectros de EL manifestou uma dependência quase linear com a densidade de corrente para ambas as polarizações. As medidas de EL em campos alternados exibiram um espectro de emissão composto pela soma das bandas obtidas separadamente em cada uma das polarizações. Medidas de EL em diferentes temperaturas (50-300 K) foram realizadas para investigar a influência da temperatura nos processos de recombinação radiativa. A intensidade exibiu uma redução com o aumento da temperatura, devido ao aumento do acoplamento elétron-fônon. / Silicon nitride with excess of nitrogen thin films were deposited on silicon substrate by reactive sputtering in order to obtain light emitting structures. Samples were modified by ion implantation of arsenic (As) and boron (B) to ascertain dopant leverage at photoluminescence (PL) spectra. PL measurements were performed at temperature ranging from 15 K up to 300 K and showed a band emission between wavelength 370 and 870 nm. An emission centered at 725 nm was observed in doped samples; especially in the presence of As. Microscope images showed crystalline structures of α-Si3N4, β-Si3N4 and γ-Si3N4 and confirmed boron dopant in nanocrystalline structures. Pool-Frenkel conduction model dominates electron transport in non-stoichiometric silicon nitride films due to intraband levels, phenomenon that has a huge contribution to electroluminescence (EL) emission. EL signals were composed by two peaks centered at 760 and 880 nm (negative bias – EL-N) and one peak at 1010 nm (positive bias – EL-P). Diffences between PL and EL spectra exhibit a clear dependence on the mode of excitation (photo and current source) on radiative recombination process. EL intensity had almost a linear increase with current density for both polarizations. EL measurements under AC voltage were composed by a superposition of the signals from EL-N and EL-P signals. Photo and electroluminescence measurements were collected at different temperatures (50 to 300 K) in order to investigate the temperature influence on the radiative recombination. The EL intensity was decreasing with temperature increasing, due to electron-phonon interactions.

Made available in DSpace on 2014-06-11T19:31:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-17Bitstream added on 2014-06-13T20:21:45Z : No. of bitstreams: 1 leite_dmg_dr_bauru.pdf: 3640633 bytes, checksum: adf6650360687a658c11b1cc1b69b693 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A recente busca por semicondutores magnéticos diluídos com propriedades magnéticas de interesse motivou este trabalho de crescimento de filmes de Ga1-xMnxN pelas técnicas de sputtering e epitaxia da fase de vapor de organometálicos (MOVPE). Os filmes são caracterizados estruturalmente por medidas de difração de raio X e microscopia eletrônica de transmissão, opticamente por transmitância óptica e espalhaçamento Raman, e magneticamente por medidas magnetização versus campo aplicado e versus temperatura. As principais diferenças entre os filmes de GaMnN preparados por sputerring e MOVPE referem-se à microestrutura e ao conteúdo de Mn: os primeiros são policristalinos e apresentam conteúdo de Mn até 9%, enquanto os últimos são monocristalinos com concentração de Mn até 1%. A alta concentraçao de Mn nos filmes crescidos por sputtering é possivelmente responsável pelo surgimento coletivo destes íons de Mn nas medidas magnéticas. Esse comportamento coletivo se identifica a partir de contribuição paramagnética de domínios isolados com alto vapor de momento magnético, o que se mostra consistente com a microestrutura apresentada por estes filmes. A alta concentração de Mn nos filmes preparados por sputtering também se mostra responsável por intensa absorção óptica abaixo da energia do gap, sendo esta relacionada a transições eletrônicas entre os estados localizados do Mn e as bandas de valência e condução do GaN. O contraste entre as propriedades dos filmes de GaMnN produzidos por sputtering e por MOVPE possibilita então um entendimento mais abrangente dos aspectos da incorporação de Mn no GaN e suas respectivas características estruturais, ópticas e magnéticas. Esse entendimento é importante para delinear a otimização deste material visando propriedades magnéticas de interesse / The current search for dilluted magnetic semiconductors with interesting magnetic properties has motivated the present work on growing GaMnN films by sputerring and metalorganic vapor phase epitaxy (MOVPE) techniques. The films are characterized by X-ray diffraction, transmission electron microscopy, optical transmission, Raman scattering, and by magnetization measurements. The main differece between the GaMnN grown by sputtering and those grown by MOVPE relates to their microstructure (polycrystalline/monocrystalline) and Mn content (up to 9%/1% respectively). The high Mn content in GaMnN samples grown by sputtering is probably responsible for a collective response on the magnetic measurements. This collective Mn response is identified as a high magnetic moment contribution which is consistent with sample microstructure. In the sputtered samples, the high Mn content is also responsible for strong subbandgap optical absorption related to eletronic transitions involving Mn states and the valence and conduction bands of GaN. The comparison between the properties of GaMnN films grown by different techniques is important in order to get a better understanding about the Mn incorporation in GaN. This understanding been important to define the next steps regarding the optimization of this material

The rapid progress of n-type metal oxide thin film transistors (TFTs) has motivated research on p-type metal oxide TFTs in order to realise metal oxide-based CMOS circuits which enable low power consumption large-area electronics. Cuprous oxide (Cu2O) has previously been proposed as a suitable active layer for p-type metal oxide TFTs. The two most significant challenges for achieving good quality Cu2O TFTs are to overcome the low field-effect mobility and an unacceptably high off-state current that are a feature of devices that have been reported to date. This dissertation focuses on improving the carrier mobility, and identifying the main origins of the low field-effect mobility and high off-state current in Cu2O TFTs. This work has three major findings. The first major outcome is a demonstration that vacuum annealing can be used to improve the carrier mobility in Cu2O without phase conversion, such as oxidation (CuO) or oxide reduction (Cu). In order to allow an in-depth discussion on the main origins of the very low carrier mobility in as-deposited films and the mobility enhancement by annealing, a quantitative analysis of the relative dominance of the main conduction mechanisms (i.e. trap-limited and grain-boundary-limited conduction) is performed. This shows that the low carrier mobility of as-deposited Cu2O is due to significant grain-boundary-limited conduction. In contrast, after annealing, grain-boundary-limited conduction becomes insignificant due to a considerable reduction in the energy barrier height at grain boundaries, and therefore trap-limited conduction dominates. A further mobility improvement by an increase in annealing temperature is explained by a reduction in the effect of trap-limited conduction resulting from a decrease in tail state density. The second major outcome of this work is the observation that grain orientation ([111] or [100] direction) of sputter-deposited Cu2O can be varied by control of the incident ion-to-Cu flux ratio. Using this technique, a systematic investigation on the effect of grain orientation on carrier mobility in Cu2O thin films is presented, which shows that the [100] Cu2O grain orientation is more favourable for realising a high carrier mobility. In the third and final outcome of this thesis, the temperature dependence of the drain current as a function of gate voltage along with the C-V characteristics reveals that minority carriers (electrons) cause the high off-state current in Cu2O TFTs. In addition, it is observed that an abrupt lowering of the activation energy and pinning of the Fermi energy occur in the off-state, which is attributed to subgap states at 0.38 eV below the conduction band minimum. These findings provide readers with the understanding of the main origins of the low carrier mobility and high off-state current in Cu2O TFTs, and the future research direction for resolving these problems.

Zinc oxide is a very versatile material that can be used in many microsystems and MEMS applications. ZnO thin film has been utilized in a wide variety of MEMS devices because of its unique piezoelectric, optical, and electrical properties. In particular, piezoelectric property of ZnO can be used in numerous applications from resonators and filters to mass sensors and micro-actuators (e.g., micro-valve and micro-pump). Because of its versatility, this research was focused on analyzing some key properties of ZnO thin film achieved by two different deposition techniques, Pulsed Laser Deposition (PLD) and Sputtering. Multiple experiments were conducted in order to identify the best conditions for the growth of ZnO thin film. Under the optimum conditions, the ZnO thin films will provide the best piezoelectric performance in devices such as microcantilevers. In order to find the best deposition conditions in both PLD and Sputtering multiple depositions have been done and then analyzed using the XRD, AFM, FTIR, nanoindenter, and ellipsometer. For the PLD the best conditions were found to be at 200°C with a partial pressure of O2 of 100 millitorr. For the sputtering system the best film formed when the substrate temperature was kept at 400°C along with RF power of 250 Watts, and a flow rate of 25% O2 and 75% Ar. Both experiments were similar in the fact that both a certain amount of O2 in the chamber and an elevated temperature are needed to facilitate the formation of ZnO crystal structure.