The theoretical part of the thesis is focused on surface treatments, their evaluation from the point of view visual properties, plasma-enhanced chemical vapor deposition and analysis of thin layers prepared by plasma polymerization. The experimental part of the thesis deals with surface treatment of stainless steel AISI 304. Thin layers of pp-HMDSO (plasma-polymer) and of DLC are deposited on the steel´s surface for the purpose of preparing transparent layer, which protect steel´s surface against of making finger prints visible. As an objective method is chosen an immersion test in artificial sweat solution according to standard ČSN EN ISO 105-E04. Evaluation of the test is measured by a gloss-meter and by a colorimeter. Prepared layers are identificated by FTIR method.

La limite théorique d’efficacité d’une cellule solaire simple jonction est de ~29 %. Afin de dépasser cette limite, une des moyens les plus prometteurs est de combiner le silicium avec des matériaux III-V. Alors que la plupart des solutions proposées dans la littérature proposent de faire croître directement le matériau III-V sur substrat silicium, ce travail présente une approche innovante de fabriquer ces cellules solaires tandem. Nous proposons une approche inverse métamorphique, où le silicium cristallin ou SiGe est cru directement sur le matériau III-V par PECVD. La faible température de dépôt (< 200 °C) diminue les problèmes de différence de dilatation thermique, et le fait de croître le matériau IV sur le matériau III-V élimine les problèmes de polarité.La réalisation de la cellule tandem finale en SiGe/AlGaAs passe par le développement et l’optimisation de plusieurs briques technologiques. Tout d’abord, nous développons l’épitaxie à 175 °C de Si(Ge) sur des substrats de Si (100) dans un réacteur de RF-PECVD industriel. La réalisation de cellules solaires à hétérojonction à partir de ce matériau Si(Ge) crû par PECVD montre que ses performances électriques s’avèrent prometteuses. Nous obtenons pour un absorbeur de 1.5 µm des Voc qui atteignent 0.57 V. L’incorporation de Ge permet d’augmenter le JSC de 15.4 % jusqu’à 16.6 A/cm2 pour Si0.72Ge0.28.En parallèle, la croissance de cellules solaires AlGaAs a été développée, ainsi que sa fabrication technologique. Nous obtenons une efficacité de 17.6 % pour une cellule simple en Al0.22Ga0.78As. Nous développons aussi des jonctions tunnel, parties essentielles d’une cellule tandem dans une configuration à deux terminaux. Nous développons notamment le dopage n du GaAs en utilisant le précurseur DIPTe, et obtenons des jonctions tunnel ayant des courants pic atteignant jusqu’à 3000 A/cm2, rejoignant ainsi les résultats de l’état de l’art.Ensuite, nous étudions l’hétéro-épitaxie de Si sur GaAs par PECVD. Le c-Si montre d’excellentes propriétés structurales. Les premiers stades de croissance sont étudiés par diffraction des rayons X avec rayonnement synchrotron. Nous trouvons un comportement inattendu : le Si est relâché dès les premiers nanomètres, mais sa maille est tétragonale. Alors que le GaAs a un paramètre de maille plus grand que le Si, le paramètre hors du plan (a⏊) du Si est plus élevé que son paramètre dans le plan (a//). Nous trouvons une forte corrélation entre cette tétragonalité et la présence d’hydrogène dans la couche de silicium. D’autre part, nous montrons que le plasma d’hydrogène présent lors du dépôt PECVD affecte les propriétés du GaAs : son dopage diminue d’environ un ordre de grandeur lorsque le GaAs est exposé au plasma H2, dû à la formation de complexes entre le H et le dopant (C, Te ou Si). Le dopage initial peut être retrouvé après un recuit à 350 °C.Enfin, nous étudions la dernière étape de fabrication de la cellule tandem : le collage. Nous avons pu reporter une cellule simple inversée en AlGaAs sur un substrat hôte (en Si), retirer le substrat GaAs et effectuer les étapes de microfabrication sur un substrat 2 pouces. Des couches épaisses de Si (>1 µm) ont été crues avec succès sur une cellule AlGaAs inversée suivie d’une jonction tunnel. Le collage de cette cellule tandem, et la processus de fabrication technologique du dispositif final sont ensuite étudiés, afin de pouvoir caractériser électriquement la première cellule solaire tandem fabriquée par croissance inverse métamorphique de Si sur III-V. / Combining Silicon with III-V materials represents a promising pathway to overcome the ≈29% efficiency limit of a single c-Si solar cell. While the standard approach is to grow III-V materials on Si, this work deals with an innovative way of fabricating tandem solar cells. We use an inverted metamorphic approach in which crystalline silicon or SiGe is directly grown on III-V materials by PECVD. The low temperature of this process (<200 °C) reduces the usual thermal expansion problems, and growing the group IV material on the III-V prevents polarity issues.The realization of the final tandem solar cell made of SiGe/AlGaAs requires the development and optimization of various building blocks. First, we develop the epitaxy at 175°C of Si(Ge) on (100) Si substrates in an industrial standard RF-PECVD reactor. We prove the promising electrical performances of such grown Si(Ge) by realizing PIN heterojunction solar cells with 1.5µm epitaxial absorber leading to a Voc up to 0.57 V. We show that the incorporation of Ge in the layer increases the Jsc from 15.4 up to 16.6 A/cm2 (SiGe28%).Meanwhile, we develop the growth of AlGaAs solar cells by MOVPE and its process flow. We reach an efficiency of 17.6 % for a single Al0.22GaAs solar cell. We then develop the tunnel junction (TJ), essential part of a tandem solar cell with 2-terminal integration. We develop the growth of n-doped GaAs with DIPTe precursor to fabricate TJs with peak tunneling currents up to 3000 A/cm2, reaching state-of-the art TJs.Then, the hetero-epitaxy of Si on GaAs by PECVD is studied. c-Si exhibits excellent structural properties, and the first stages of the growth are investigated by X-ray diffraction with synchrotron beam. We find an unexpected behavior: the grown Si is fully relaxed, but tetragonal. While the GaAs lattice parameter is higher than silicon one, we find a higher out-of-plane Si parameter (a⏊) than in-plane (a//), contradicting the common rules of hetero-epitaxy. We find a strong correlation between this tetragonal behavior and the presence of hydrogen in the Si layer. We furthermore show that hydrogen also plays a strong role in GaAs: the doping level of GaAs is decreased by one order of magnitude when exposed to a H2 plasma, due to the formation of complexes between H and the dopants (C, Te, Si). This behavior can be recovered after annealing at 350°C.Finally, the last step of device fabrication is studied: the bonding. We successfully bonded an inverted AlGaAs cell, removed it from its substrate, and processed a full 2” wafer. We succeeded in growing our first tandem solar cells by growing thick layers (>1 µm) of Si on an inverted AlGaAs solar cells followed by a TJ. The bonding and process of this final device is then performed, leading, as a next step, to the electrical measurement of the very first tandem solar cell grown by inverted metamorphic growth of Si on III-V.

Neste trabalho é realizado o estudo das etapas de fabricação de um dispositivo eletro-termo-óptico. O dispositivo baseia-se em um interferômetro Mach-Zehnder (IMZ) onde um micro-resistor é colocado em um dos braços do IMZ. Este interferômetro foi construído usando guias de onda ARROW (Anti-Resonant Reflecting Optical Waveguide) onde filmes de oxinitreto de silício e carbeto de silício amorfo hidrogenado foram utilizados como materiais constituintes. Estes materiais foram depositados pela técnica de PECVD (Plasma Enhanced Chemical Vapor Deposition) a baixas temperaturas (~300°C) usando silano (SiH4), nitrogênio (N2), hidrogênio (H2), oxido nitroso (N2O) e metano (CH4) como gases precursores. Para isolar termicamente a região de aquecimento do dispositivo, parte do braço sensor do IMZ foi suspenso através da corrosão superficial do substrato de silício em solução de hidróxido de potássio (KOH). Basicamente o dispositivo termo-eletroóptico utiliza para seu funcionamento o efeito termo-óptico dos materiais constituintes. Neste caso, com a aplicação de uma corrente elétrica no micro-resistor localizado em uma pequena região de um dos braços do IMZ é produzido uma variação na temperatura e no índice de refração dos filmes próximos ao microresistor. Com isto, o aparecimento de uma diferença de fase entre as ondas propagantes dos dois braços do IMZ é ocasionado e, como conseqüência, uma interferência eletromagnética dependente da diferença de fase das ondas propagantes causada pela variação de temperatura é originado. Dessa maneira, é possível fabricar um dispositivo termo-eletro-óptico onde uma variação da corrente aplicada no micro-resistor produz uma alteração da potência óptica na saída do interferômetro. / In this work, a study of the steps to fabricate an electro-thermo-optical device is realized. This device is based in a Mach-Zehnder interferometer (IMZ) where a micro-resistor is placed in one of the IMZ arms. The Mach-Zehnder interferometer was fabricated using Anti-Resonant Reflecting Optical Waveguide (ARROW) where oxinytride and amorphous hydrogenated silicon carbide films were used as constituent materials. These materials were deposited by PECVD (Plasma Enhanced Chemical Vapor Deposition) technique at low temperatures (~300°C) using silane (SiH4), nitrogen (N2), hydrogen (H2), nitrous oxide (N2O) and methane (CH4) as precursor gases. In order to isolate thermally the heating region of the structure, part of the IMZ sensor arm was suspended by the surface etching of the silicon substrate in KOH solution. Basically, the electro-thermo-optical device is based in the Thermo- Optic Effect of the constituent materials. In this case, with the application of an electrical current in the micro-resistor located in a small region of the sensor arm of the IMZ, a change in the temperature and in the refractive index of the films close to the micro-resistor is produced. So, a phase difference between the electromagnetic waves that travel by the two arms of the IMZ is produced and, as consequence, an electromagnetic interference dependent of the temperature variation is originated. In this way, it is possible fabricate an electro-thermo-optical device where the optical power output depends of the electrical current applied to a micro-resistor.

Neste trabalho é realizado o estudo das etapas de fabricação de um dispositivo eletro-termo-óptico. O dispositivo baseia-se em um interferômetro Mach-Zehnder (IMZ) onde um micro-resistor é colocado em um dos braços do IMZ. Este interferômetro foi construído usando guias de onda ARROW (Anti-Resonant Reflecting Optical Waveguide) onde filmes de oxinitreto de silício e carbeto de silício amorfo hidrogenado foram utilizados como materiais constituintes. Estes materiais foram depositados pela técnica de PECVD (Plasma Enhanced Chemical Vapor Deposition) a baixas temperaturas (~300°C) usando silano (SiH4), nitrogênio (N2), hidrogênio (H2), oxido nitroso (N2O) e metano (CH4) como gases precursores. Para isolar termicamente a região de aquecimento do dispositivo, parte do braço sensor do IMZ foi suspenso através da corrosão superficial do substrato de silício em solução de hidróxido de potássio (KOH). Basicamente o dispositivo termo-eletroóptico utiliza para seu funcionamento o efeito termo-óptico dos materiais constituintes. Neste caso, com a aplicação de uma corrente elétrica no micro-resistor localizado em uma pequena região de um dos braços do IMZ é produzido uma variação na temperatura e no índice de refração dos filmes próximos ao microresistor. Com isto, o aparecimento de uma diferença de fase entre as ondas propagantes dos dois braços do IMZ é ocasionado e, como conseqüência, uma interferência eletromagnética dependente da diferença de fase das ondas propagantes causada pela variação de temperatura é originado. Dessa maneira, é possível fabricar um dispositivo termo-eletro-óptico onde uma variação da corrente aplicada no micro-resistor produz uma alteração da potência óptica na saída do interferômetro. / In this work, a study of the steps to fabricate an electro-thermo-optical device is realized. This device is based in a Mach-Zehnder interferometer (IMZ) where a micro-resistor is placed in one of the IMZ arms. The Mach-Zehnder interferometer was fabricated using Anti-Resonant Reflecting Optical Waveguide (ARROW) where oxinytride and amorphous hydrogenated silicon carbide films were used as constituent materials. These materials were deposited by PECVD (Plasma Enhanced Chemical Vapor Deposition) technique at low temperatures (~300°C) using silane (SiH4), nitrogen (N2), hydrogen (H2), nitrous oxide (N2O) and methane (CH4) as precursor gases. In order to isolate thermally the heating region of the structure, part of the IMZ sensor arm was suspended by the surface etching of the silicon substrate in KOH solution. Basically, the electro-thermo-optical device is based in the Thermo- Optic Effect of the constituent materials. In this case, with the application of an electrical current in the micro-resistor located in a small region of the sensor arm of the IMZ, a change in the temperature and in the refractive index of the films close to the micro-resistor is produced. So, a phase difference between the electromagnetic waves that travel by the two arms of the IMZ is produced and, as consequence, an electromagnetic interference dependent of the temperature variation is originated. In this way, it is possible fabricate an electro-thermo-optical device where the optical power output depends of the electrical current applied to a micro-resistor.

Nesta dissertação discorremos acerca do crescimento e caracterização de filmes finos de carbeto de silício amorfo hidrogenado (a-Si1-xCx:H), crescidos pelo método de deposição química de vapor assistida por plasma (PECVD) no regime de baixa densidade de potência a partir de misturas de silano e metano. Foram analisadas e correlacionadas as propriedades ópticas, morfológicas e composicionais de filmes depositados em diferentes condições de fluxo de silano e concentração de metano. Os resultados não apenas confirmaram dados anteriores obtidos em filmes de a-Si1-xCx:H similares, mas possibilitaram uma melhor compreensão das características deste material. Para a obtenção de um composto de alto gap, alto conteúdo de carbono, química e morfologicamente homogêneo é necessário utilizar baixos fluxos de silano e alta concentração de metano, condições de deposição conhecidas como regime de \"plasma faminto por silano\". Neste regime são crescidos filmes com Eg &gt; 3 eV, x &gt; 0,5, maior concentração de ligações Si-C, concentração de hidrogênio de 50 at.%, menor proporção de radicais CH3 e menor densidade de poros. / In this work we describe the growth and characterization of hydrogenated amorphous silicon carbide (a-Si1-xCx:H) thin films deposited by plasma enhanced chemical vapor deposition (PECVD) in the low power density regime from mixtures of silane and methane. The optical, morphological and compositional properties of films deposited under different silane flow and methane concentration were analyzed and correlated. The results not only confirmed previous data obtained on similar a-Si1-xCx:H films, but improved the comprehension of their characteristics. In order to obtain a compound with high optical gap, high carbon content, chemically and morphologically homogeneous, it is necessary to work with low silane flow and high methane concentration; deposition conditions known as \"silane starving plasma\" regime. In this regime, films with Eg &gt; 3 eV, x &gt; 0.5, higher concentration of Si-C bonds, hydrogen concentration of 50 at.%, smaller proportion of CH3 radicals and smaller density of pores are produced.

Nesta dissertação discorremos acerca do crescimento e caracterização de filmes finos de carbeto de silício amorfo hidrogenado (a-Si1-xCx:H), crescidos pelo método de deposição química de vapor assistida por plasma (PECVD) no regime de baixa densidade de potência a partir de misturas de silano e metano. Foram analisadas e correlacionadas as propriedades ópticas, morfológicas e composicionais de filmes depositados em diferentes condições de fluxo de silano e concentração de metano. Os resultados não apenas confirmaram dados anteriores obtidos em filmes de a-Si1-xCx:H similares, mas possibilitaram uma melhor compreensão das características deste material. Para a obtenção de um composto de alto gap, alto conteúdo de carbono, química e morfologicamente homogêneo é necessário utilizar baixos fluxos de silano e alta concentração de metano, condições de deposição conhecidas como regime de \"plasma faminto por silano\". Neste regime são crescidos filmes com Eg &gt; 3 eV, x &gt; 0,5, maior concentração de ligações Si-C, concentração de hidrogênio de 50 at.%, menor proporção de radicais CH3 e menor densidade de poros. / In this work we describe the growth and characterization of hydrogenated amorphous silicon carbide (a-Si1-xCx:H) thin films deposited by plasma enhanced chemical vapor deposition (PECVD) in the low power density regime from mixtures of silane and methane. The optical, morphological and compositional properties of films deposited under different silane flow and methane concentration were analyzed and correlated. The results not only confirmed previous data obtained on similar a-Si1-xCx:H films, but improved the comprehension of their characteristics. In order to obtain a compound with high optical gap, high carbon content, chemically and morphologically homogeneous, it is necessary to work with low silane flow and high methane concentration; deposition conditions known as \"silane starving plasma\" regime. In this regime, films with Eg &gt; 3 eV, x &gt; 0.5, higher concentration of Si-C bonds, hydrogen concentration of 50 at.%, smaller proportion of CH3 radicals and smaller density of pores are produced.

Researchers at Brigham Young University (BYU) have developed an optical biosensor that can quickly analyze a sample to detect any type of nucleic acid based organism, such as viruses or bacteria. The biosensor's reliability over time is compromised due to water absorbing into the SiO2 waveguides of the chip. It was hypothesized that keeping the thin-film stress of the waveguides close to zero would slow or stop water absorption from occurring. Completion of this thin-film study relied upon a new plasma enhanced chemical vapor deposition (PECVD) machine and a new 3-D optical profilometer, both of which were installed in the BYU cleanroom. The new PECVD machine was much more capable than previous machines at controlling deposition parameters and was a critical component in accurately controlling the intrinsic stress of deposited films. The 3-D optical profilometer provided us a way to accurately measure the intrinsic stress of the films. Rib waveguides made from different stressed SiO2 films were fabricated over anti-resonant reflecting optical waveguide (ARROW) layers. The wafers were baked out, cleaved, and their initial throughputs recorded. All waveguides were placed in a humid environment and were removed periodically to check their optical throughput. The resulting measurements were normalized to the highest measured throughput to determine how throughput was changing over time. Rib waveguides with the lowest stressed SiO2 had the slowest rate of throughput change, dropping to 50% of the original throughput after 40 days in the humid environment. The +50 MPa stressed waveguides performed next best, dropping to 20% of the original throughput after 40 days. The +100 MPA stressed waveguides dropped to 20% throughput after 16 days while the -50 MPa stressed wafers dropped to 20% optical throughput after 7 days. Keeping the stress of the film as low as possible helped reduce the rate of water absorption, but did not eliminate it completely. A method involving the use of high index difference buried channel waveguides is shown to be effective at stopping the effects of water absorption in our waveguides.

Silicon heterojunction solar cells, a-Si:H/c-Si, are promising technology for future photovoltaic systems. An a-Si:H/c-Si heterojunction solar cell combines the advantages of single crystalline silicon photovoltaic with thin-film technologies. This thesis reports a detailed survey of heterojunction silicon solar cells with p-type wafer fabricated by magnetron sputtering and Plasma Enhanced Chemical Vapor Deposition (PECVD) techniques at low processing temperature. In the first part of this study, magnetron sputtering method was employed to fabricate a-Si:H thin films and then a-Si:H/c-Si solar cells. Amorphous silicon (a-Si:H) films were grown on glass in order to perform electrical and optical characterizations. The J-V characteristics of the silicon heterojunction solar cells were analyzed as a function of a-Si:H properties. It was shown that a-Si thin films with well-behaved chemical and electronic properties could be fabricated by the magnetron sputtering. Hydrogenation of the grown film could be achieved by H2 introduction into the chamber during the sputtering. In spite of the good film properties, fabricated solar cells had poor photovoltaic parameters with a low rectification characteristic. This low device performance was caused by high resistivity and low doping concentration in the sputtered film. The second part of the thesis is dedicated to heterojunction solar cells fabricated by PECVD. In this part a systematic study of various PECVD processing parameters were carried out to optimize the a-Si:H(n) emitter properties for the a-Si:H(n)/c-Si(p) solar cell applications. In the next stage, a thin optimized a-Si:H(i) buffer layer was included on the emitter side and on the rear side of the c-Si(p) to improve the surface passivation. Insertion of an a-Si:H(i) buffer layer yielded higher high open circuit voltage (Voc) with lower fill factor. It was shown that high Voc is due to the efficient surface passivation by the front/rear intrinsic layer which was also confirmed by the measurement of high effective lifetime for photo-generated carriers. Low fill factor on the other hand is caused by increasing resistivity of the solar cells by inserting low conductivity a-Si:H(i) layers.

Silicon oxynitride (SiON) films for applications of optical waveguide devices deposited using plasma-enhanced chemical vapor deposition were investigated. The SiON films were deposited on 4¡¨ silicon wafers based on the reaction of N2O/SiH4 precursors. The refractive indices of the films were adjusted by varying the partial pressure of SiH4 in the precursors. In addition, films prepared at conventional flow (~1500 sccm) and low flow (~1000 sccm) conditions were compared. We found that the nitrogen content of the films grown at low flow conditions can be significantly reduced resulting in a reduction of absorption around 1500 nm. Therefore SiON films grown at low flow conditions would be more suitable for optical waveguide fabrication. Finally, with the aid of the beam propagation method (BPM) software, a single-mode optical waveguide based on the proposed technology was designed and fabricated. The propagation loss was 0.79dB/cm for TE polarization, and 0.73db/cm for T

Hydrogenated amorphous silicon carbide (a-SiC:H) can provide exceptional surface passivation essential for high-efficiency crystalline silicon solar cells. This thesis reports on the fundamental study of a-SiC:H films deposited using a novel deposition technique, DC saddle field PECVD, in contrast to the conventional industrial use of RF-PECVD. The growth conditions were optimized and correlated with passivating, structural, and optical characteristics. The lifetime has a strong dependency on deposition temperature and improves by over two orders of magnitude as the temperature increases; the maximum lifetime achieved in this work reached 0.5 ms. In addition, the Tauc optical gap can be increased from 1.7 eV to 2.3 eV by varying the precursor gas mixture ratio. Post-deposition annealing experiments demonstrate thermal stability of the samples deposited at 250 °C and in some instances shows improvement in passivation quality by a factor of two with a one-step annealing treatment at 300 °C for 15 minutes.