No description available.

Transparent conducting oxides (TCOs) combine optical transparency in the visible region with a high electrical conductivity. In2O3 doped with Sn (widely, but somewhat misleadingly, known as indium tin oxide or ITO) is at present the most important TCO, with applications in liquid crystal displays, touch screen displays, organic photovoltaics and other optoelectronic devices. Surprisingly, many of its fundamental properties have been the subject of controversy or have until recently remained unknown, including even the nature and magnitude of the bandgap. The technological importance of the material and the renewed interest in its basic physics prompted the research described in this thesis. This thesis aims (i) to establish conditions for the growth of high-quality In2O3 nanostructures and thin films by oxygen plasma assisted molecular beam epitaxy and (ii) to conduct comprehensive investigations on both the surface physics of this material and its structural and electronic properties. It was demonstrated that highly ordered In2O3 nanoislands, nanorods and thin films can be grown epitaxially on (100), (110) and (111) oriented Y-stabilized ZrO2 substrates respectively. The mismatch with this substrate is -1.7%, with the epilayer under tensile strain. On the basis of ab initio density functional theory calculations, it was concluded that the striking influence of substrate orientation on the distinctive growth modes was linked to the fact that the surface energy for the (111) surface is much lower than for either polar (100) or non-polar (110) surfaces. The growth of In2O3(111) thin films was further explored on Y-ZrO2(111) substrates by optimizing the growth temperature and film thickness. Very thin In2O3 epilayers (35 nm) grew pseudomorphically under high tensile strain, caused by the 1.7% lattice mismatch with the substrate. The strain was gradually relaxed with increasing film thickness. High-quality films with a low carrier concentration (5.0  1017 cm-3) and high mobility (73 cm2V-1s-1) were obtained in the thickest films (420 nm) after strain relaxation. The bandgap of the thinnest In2O3 films was around 0.1 eV smaller than that of the bulk material, due to reduction of bonding-antibonding interactions associated with lattice expansion. The high-quality surfaces of the (111) films allowed us to investigate various aspects of the surface structural and electronic properties. The atomic structure of In2O3 (111) surface was determined using a combination of scanning tunnelling microscopy, analysis of intensity/voltage curves in low energy electron diffraction and first-principles ab initio calculations. The (111) termination has an essentially bulk terminated (1 × 1) surface structure, with minor relaxations normal to the surface. Good agreement was found between the experimental surface structure and that derived from ab initio density functional theory calculations. This work emphasises the benefits of a multi-technique approach to determination of surface structure. The electronic properties of In2O3(111) surfaces were probed by synchrotron-based photoemission spectroscopy using photons with energies ranging from the ultraviolet (6 eV) to the hard X-ray regime (6000 eV) to excite the spectra. It has been shown that In2O3 is a highly covalent material, with significant hybridization between O and In orbitals in both the valence and the conduction bands. A pronounced electron accumulation layer presents itself at the surfaces of undoped In2O3 films with very low carrier concentrations, which results from the fact the charge neutrality level of In2O3 lies well above the conduction band minimum. The pronounced electron accumulation associated with a downward band bending in the near surface region creates a confining potential well, which causes the electrons in the conduction band become quantized into two subband states, as observed by angle resolved photoemission spectra (ARPES) Fermi surface mapping. The accumulation of high density of electrons near to the surface region was found to shrink the surface band gap through many body interactions. Finally epitaxial growth of In2O3 thin films on α-Al2O3(0001) substrates was investigated. Both the stable body centred cubic phase and the metastable hexagonal corundum In2O3 phase can be stabilized as epitaxial thin films, despite large mismatches with the substrate. The growth mode involves matching small but different integral multiples of lattice planes of the In2O3 and the substrate in a domain matching epitaxial growth mode.

Porous metal oxides formed by supercritical carbon dioxide (SCCO2) treatments at low temperature were used for displays, solar cells, and light emitting diodes (LEDs) applications. The SCCO2 fluid, also known as green solvents, exhibits low viscosity, low surface tension and high diffusivity as gases, and high density and solubility same with liquids. In this thesis, we successfully fabricated porous antimony-doped tin oxide (ATO) and porous indium tin oxide (ITO) by the SCCO2 treatments. In addition, the treatment can also be used to improve the work function and surface energy of ITO anode of an organic LED (OLED). The performance of the OLEDs was drastically enhanced in comparison with that of the devices without any ITO surface treatments. First, the porous ATO films were formed by the SCCO2 treatment for absorption of silver molecules in silver electro deposition devices. The porosity, resistivity and average optical transmittance of the porous ATO film in visible wavelength were 43.1%, 3 £[-cm and 90.4%, respectively. For the silver electro deposition devices with the porous ATO film, the transmittance contrast ratio of larger than 12 in visible spectrum was obtained at an operating voltage of 1.5 V. Furthermore, for the 0.25 cm2 device, the switching time of 4.5 seconds was achieved by applying a square-wave voltage ranging from 1.5 to -0.2 V between the electrodes. On the other hand, the porous ITO with low refractive index was prepared by SCCO2/IPA treatment on gel-coated ITO thin films. The high refractive index of the ITO film was achieved by long-throw radio-frequency magnetron sputtering technique at room temperature. The index contrast (£Gn) was higher than 0.6 between porous ITO and sputtered ITO films. The large £Gn is useful for fabricating conductive anti-reflection (AR) and high reflection (HR) structures using the porous ITO on sputtered ITO bilayers. The weighted average reflectance and transmittance of 4.3% and 83.1% were achieved for the double-layer ITO AR electrode with a sheet resistance of 1.1 K£[/¡E. For HR structures, the reflectance and sheet resistance were 87.9% and 35 £[/¡E with 4 periods ITO bilayers. Finally, the SCCO2 treatments with strong oxidizer H2O2 were proposed to modify surface property of ITO anode of a fluorescent OLED. The highest work function and surface energy of 5.5 eV and 74.8 mJ/m2 was achieved by the SCCO2/H2O2 treatment. For the OLED with 15 min SCCO2 treatment at 4000 psi, the turn-on voltage and maximum power efficiency of 6.5 V and 1.94 lm/W were obtained. The power efficiency was 19.3% and 33.8% higher than those of the OLEDs with oxygen plasma treated and as-cleaned ITO anodes.

Polymer/inorganic nanoparticle hybrid thin films, primarily composed of functional inorganic nanoparticles, are of great interest to researchers because of their interesting electronic, photonic, and optical properties. In the past two decades, layer-by-layer (LbL) assembly has become one of the most powerful techniques to fabricate such hybrid thin films. This method offers an easy, inexpensive, versatile, and robust fabrication technique for multilayer formation, with precisely controllable nanostructure and tunable properties. In this thesis, various ways to control the structure of hybrid thin films, primarily composed of polyelectrolytes and indium tin oxide (ITO), are the main topics of study. ITO is one of the most widely used conductive transparent oxides (TCOs) for applications such as flat panel displays, photovoltaic cells, and functional windows. In this work, polyethyleneimine (PEI) was used to stabilize the ITO suspensions and improve the film buildup rate during the LbL assembly of poly(sodium 4-styrenesulfonate) (PSS) and ITO. The growth rate was doubled due to the stronger interaction forces between the PSS and PEI-modified ITO layer. The assembly of hybrid films was often initiated by a polyelectrolyte precursor layer, and the characteristics of the precursor layer were found to significantly affect the assembly of the hybrid thin films. The LbL assembly of ITO nanoparticles was realized on several substrates, including cellulose fibers, write-on transparencies, silicon wafers, quartz crystals, and glasses. By coating the cellulose fibers with ITO nanoparticles, a new type of conductive paper was manufactured. By LbL assembly of ITO on write-on transparencies, transparent conductive thin films with conductivity of 10⁻⁴ S/cm and transparency of over 80 % in the visible range were also prepared. As a result of this work on the mechanisms and applications of LbL grown films, the understanding of the LbL assembly of polyelectrolytes and inorganic nanoparticles was significantly extended. In addition to working with ITO nanoparticles, this thesis also demonstrated the ability to grow bicomponent [PEI/SiO₂]n thin films. It was further demonstrated that under the right pH conditions, these films can be grown exponentially (e-LbL), resulting in much thicker films, consisting of mostly the inorganic nanoparticles, in much fewer assembly steps than traditional linearly grown films (l-LbL). These results open the door to new research opportunities for achieving structured nanoparticle thin films, whose functionality depends primarily on the properties of the nanoparticles.

Σκοπός της παρούσας εργασίας είναι αρχικά να μελετηθεί η επιφάνεια του οξειδίου ινδίου κασσιτέρου που έχει αποτεθεί σε υπόστρωμα ΡΕΤ και να γίνουν πάνω σε αυτήν χημικές επεξεργασίες αλλά και ιοντοβολή, ώστε να παρατηρηθούν τι επιδράσεις έχουν αυτές οι κατεργασίες στην επιφάνεια και ενδεχομένως στο έργο εξόδου. Οι κατεργασίες επιλέχθηκαν επειδή είναι γνωστή από την βιβλιογραφία η επίδρασής τους στο ΙΤΟ που όμως έχει αποτεθεί σε γυαλί, και η σύγκριση με τα δικά μας αποτελέσματα θα δώσει χρήσιμες πληροφορίες για τις διαφορές των δύο υλικών καθώς και αν οι κατεργασίες αυτές μπορούν να χρησιμοποιηθούν και αν είναι χρήσιμες για την αύξηση του έργου εξόδου του ΙΤΟ-ΡΕΤ. Επίσης, στη συνέχεια έγιναν αποθέσεις οργανικού ημιαγώγιμου υλικού (NiPc) πάνω στο υπόστρωμα ΙΤΟ-ΡΕΤ το οποίο είχε επεξεργαστεί χημικά, με σκοπό να προσδιοριστεί η ηλεκτρονική δομή της διεπιφάνειας του οργανικού και του υποστρώματος, ώστε να μελετηθεί η επίδραση του ΙΤΟ-ΡΕΤ στην συμπεριφορά της διεπιφάνειας και να διαπιστωθεί η πιθανή εφαρμογή τους σε ηλεκτρονικές διατάξεις. / The purpose of this thesis is to study the surface of indium tin oxide deposited on PET substrate after some chemical treatments and Argon Sputtering, in to order to investigate what effects these treatments have on the surface and possibly in the work function. The treatments were chosen because it is known from the literature the influence they have on the ITO, but which it has been deposited on glass, and a comparison of our results will provide useful information about differences between the two materials, and whether these treatments can be useful for increasing the work function of ITO-PET. Also, it was deposited organic semiconductor material (NiPc) onto the ITO-PET substrate that was chemically processed in order to determine the electronic structure at the interface of organic substrate and to study the effect of ITO-PET in the behavior of interface and to determine its possible application in electronic devices.

Elektrochemické metody nacházejí využití v mnoha aplikacích (např. senzorice, skladování el. energie nebo katalýze). Jejich nespornou výhodou je nízká finanční náročnost na přístrojové vybavení. Abychom lépe porozuměli procesům probíhajícím na elektrodách, je dobré znát elektronickou pásovou strukturu materiálu elektrody. Úkolem této práce je vyhodnotit výstupní práci a pozici hrany valenčního pásu nových materiálů pro elektrody, konkrétně cínem dopovaného oxidu india pokrytého nanotrubicemi sulfidu wolframičitého. Ultrafialová fotoelektronová spektroskopie a Kelvinova silová mikroskopie jsou metody použité pro tuto analýzu. Zvláštní důraz je kladen na přípravu vzorků elektrod pro měření, aby nedošlo k nesprávné interpretaci výsledků vlivem vnějších efektů jako je např. kontaminace nebo modifikace povrchu.

Naturgas är ett alternativ till oljebaserade bränslen. Ur ett miljöperspektiv är naturgasen fördelaktig eftersom den vid förbränning ger mindre utsläpp av miljöfarliga ämnen än olja. I en diesel dual-fuel motor används diesel och naturgas som bränsle. Naturgas består till största delen av metan. För att oskadliggöra den del av metangasen som inte förbränns i motorn krävs en avgaskatalysator som kan bryta ned det relativt stabila metanet vid låga temperaturer. Målet med det här kandidatexamensarbetet är att tillverka och testa tre olika avgaskatalysatorer för nedbrytning av metan. De tre katalysatorer som valdes för tillverkning och testning var Pd/Al2O3, Pd/SnO2 och In2O3/SnO2 (ITO). Valen baserade sig på att katalysatorerna som tillverkades skulle vara aktiva för nedbrytning av metan vid låga temperaturer. ITO sågs som en extra intressant kandidat eftersom In är billigare än ädelmetallen Pd. Pd/Al2O3 tillverkades med en kommersiell support och impregnering av Pd genom ”incipient wetness” (IW). Pd/SnO2 tillverkades på samma sätt. ITO tillverkades genom ”forward co-precipitation”. En monolit testades för varje katalysator. Vid ungefär 315 °C kunde 10 % omsättning av metan detekteras för alla tre katalysatorer. Pd/Al2O3 var den katalysator vars aktivitet förbättrades som mest då temperaturen ökade ytterligare. Katalysatorerna testades bara en gång. För att statistiskt säkerställa resultaten behöver upprepade tester göras. Resultaten överensstämmer delvis med tidigare studier. Slutsatsen av arbetet är att alla tre katalysatorer fungerar och att ITO skulle kunna vara en billigare men i övrigt likvärdig avgaskatalysator för en diesel dual-fuel lean burn motor vid 315 °C. Fler tester måste dock göras för att ta reda på om ITO verkligen är ett mer fördelaktigt alternativ.

No description available.

Vanadium oxides are being used as the thermal sensing layer because of their applications in infrared detectors. They have high temperature coefficient of resistance, favorable electrical resistance and compatibility with the MEMS technology. Of all oxides of vanadium, only vanadium dioxide (VO2)has been highly investigated as it shows first order transition (semiconducting to metal transition-SMT)at 68 oC. First order transition is understood as the sharp change in the electrical resistance. The change in resistivity in this case is of the order of 105 over a temperature change of 0.1 oC at 68 oC in a single crystal. Doping vanadium oxides with elements like Mo and W reduce the transition temperature. This is very important for room temperature electrical and optical detection. Though most of the research groups subscribe to PLD, cost-effective methods with large area deposition are major focus of this research. Hence for synthesizing VO2 in bulk and thin films, Solution Combustion Synthesis (SCS), Ultrasonic Nebulized Spray Pyrolysis of Aqueous Combustion Mixture (UNSPACM) Chemical vapour deposition (CVD)and microwave are explored. Synthesis of doped VO2 films in CVD has not been done extensively to yield optical quality thin films. Chapter I surveys the use of phase transition in oxides system for a variety of practical applications. In particular, Vanadium dioxide (VO2) is chosen as it is found to be very useful for infrared and metamaterials based applications. VO2 is known for its first-order semiconducting to metallic transition (SMT). This chapter attempts to explain the influence of processing, doping, annealing, etc on the SMT characteristics. Important aspects such as the idea of hysteresis in VO2 and similarity to martensitic transformation are discussed. The scope and objectives of the thesis are discussed here. Chapter II explains in detail the materials and methods used to synthesize VO2 both in bulk and in thin lm form and methods used to study their characteristics. Brief description on the principle and the working of the home-built experimental set up needed for this study is elicited. In chapter III, attempts were made to understand the phase stability of VO2 and the evolution of crystal structures during the phase transition. VO2 crystallizes in P21/c space group at room temperatures with lattice parameters a=5.752 Ab=4.526 Ac=5.382 Aα=90 β=122.60 γ=90 . Precise control of synthesis parameters is required in stabilizing pure phase in bulk as well as thin lm form. This study focuses on the novel large scale two step synthesis of VO2 using Solution Combustion Synthesis. This involves synthesis of product utilizing redox reaction between metal nitrate and suitable fuel. Generally the products are nanocrystalline in nature due to self-propagation of the exothermic combustion reaction. First step involved the synthesis of V2O5 by combustion reaction between Vanadyl nitrate and urea. In the second step, the as-synthesized V2O5 has been reduced by a novel reduction technique to form monophasic VO2. The presence of competing phases like M1, M2, M3 and R are investigated by XRD, Raman spectroscopy, DSC, Optical and high temperature X-ray diffraction. Chapter IV deals with the reduction in phase transition temperature by doping the SCS synthesized VO2 with W and Mo. Effect of doping on the transition temperature was studied using differential scanning calorimetry (DSC) in both W and Mo. Electrical characteristics of Mo doped VO2 and Optical characteristics of the W-doped VO2 were also studied using four probe resistivity measurements and UV-VIS Spectroscopy respectively. W addition was found to be more effective in reducing the phase transition temperature. To understand further more on the W addition, X-ray photo-electron spectroscopy measurements were performed. W-addition alters the V4+-V4+ bonding and with W addition it is observed that V was present in V3+state. W was present in W6+ state. The addition of W to VO2 introduces more electrons to the systems and disturbs the V4+-V4+ thus reducing the phase transition temperature of VO2. Chapter V describes the large scale, large area deposition of thin films of VO2 by a cost effective method. A novel technique to deposit vanadium dioxide thin films namely, UNSPACM is developed. This simple two-step process involves synthesis of a V2O5 lm on an LaAlO3(LAO) substrate followed by a controlled reduction to form single phase VO2. The formation of M1 phase (P21/c) is confirmed by Raman spectroscopic studies. A thermally activated metal{insulator transition (MIT) was observed at 61 oC, where the resistivity changes by four orders of magnitude. The infrared spectra also show a dramatic change in reflectance from 13% to over 90% in the wavelength range of 7-15 m. This indicates the suitability of the films for optical switching applications at infrared frequencies. A trilayer metamaterial absorber, composed of a metal structure/dielectric spacer/vanadium dioxide (VO2) ground plane, is shown to switch reversibly between reflective and absorptive states as a function of temperature. The VO2 lm, which changes its conductivity by four orders of magnitude across an insulator{metal transition, enables the switching by forming a resonant absorptive structure at high temperatures while being inactive at low temperatures. The fabricated metamaterial shows a modulation of the reflectivity levels of 58% at a frequency of 22.5 THz and 57% at a frequency of 34.5 THz. Chapter VI explains the W doped VO2 thin films synthesized by UN-SPACM. Morphology of the thin films was found to be consisting of globular and porous nanoparticles having size 20 nm. Transition temperature decreased with the addition of W. 1.8 at. %W doping in VO2 transition temperature has reduced upto 25 oC. It is noted that W-doping in the pro-cess of reducing the transition temperature, alters the local structure and also increases room temperature carrier concentration. The presence of W, as was seen in Chapter IV, altered V4+-V4+ bonds and introduced V3+. W was found to be in W6+ state suggesting W addition increased the carrier concentration. Hall Effect measurements suggested the increased carrier con-centration. The roughness of the synthesized films were very high for them to be of de-vice quality, despite encouraging results obtained by electrical measurements. Hence in order to further improve the smoothness and thereby the optical quality of thin films, Chemical Vapour Deposition (CVD) is employed. Chapter VII outlines the effect of processing parameters and post pro-cessing annealing on the semiconductor-metallic transition of VO2. Here in this chapter, the influence of substrate temperature on the SMT properties of VO2 is explored. At different substrate temperatures, the percentage of phase fraction of V in V3+, 4+ and V5+ differed. Besides, the morphology also varied with substrate temperatures. Similarly it is observed that with annealing the VO2 film deposited on glass substrates, SMT properties enhanced which was attributed to filling out of oxygen vacancies. Si based substrates and non-Si based substrates were used for depositing VO2 thin films by CVD. Their temperature coefficient of resistance and SMT properties were studied in order to understand their potential in bolometer and thermal to optical valve based applications. Chapter VIII involves the study of VO2 thin films for thermal to optical valves. ITO coated glass substrates were used for the purpose. Thin films were deposited by both UNSPACM and CVD. It was observed that the reflectivity pro les of the films synthesized by the above said methods were very different. Hence in the process of understanding the huge difference in the reflectivity pro les, classical harmonic oscillator, Lorentzian model was employed to t the experimental data at room temperature whereas Drude-Lorentzian model was used to t the data at higher temperature (at 100 oC- after transition). With this fitting plasma frequencies of the CVD films were calculated. It was observed that defect chemistry of films synthesized by these methods were different. In order to further improve the smoothness of the films, microwave method was proposed in Chapter IX. The preliminary results showed the presence of uniform spheres and 3 D hierarchical structures of VO2 consisting of nanorods. This was extended to deposit VO2 thin films on ITO. DSC and Infrared reflectance pro le of VO2 nanopowder suggested the phase transition. Chapter X summarizes the work done for the thesis and provides insights to the applications and to the future work. The work reported in this thesis has been carried out by the candidate as part of the Ph.D.program. She hopes that this would constitute a worth-while contribution towards development of VO2 thin film technology and its challenges for reliable infrared device applications.

[ES] La búsqueda de nuevas soluciones e ideas innovadoras en el campo de la fotónica de silicio mediante la integración de nuevos materiales con prestaciones únicas es un tema de alta actualidad entre la comunidad científica en fotónica y con un impacto potencial muy alto. Dentro de esta temática, esta tesis pretende contribuir hacia una nueva generación de dispositivos fotónicos basados en la integración de óxidos metálicos en tecnología de silicio. Los óxidos metálicos elegidos pertenecen a la familia de óxidos conductores transparentes (TCO), concretamente el óxido de indio y estaño (ITO) y el óxido de cadmio (CdO), y materiales de cambio de fase (PCM) como el dióxido de vanadio (VO2). Dichos materiales se caracterizan especialmente por una variación drástica de sus propiedades optoelectrónicas, tales como la resistividad o el índice de refracción, frente a un estímulo externo ya sea en forma de temperatura, aplicación de un campo eléctrico o excitación óptica. De esta forma, nuestro objetivo es diseñar, fabricar y demostrar experimentalmente nuevas soluciones y dispositivos clave tales como dispositivos no volátiles, desfasadores y dispositivos con no linealidad óptica. Tales dispositivos podrían encontrar potencial utilidad en diversas aplicaciones que comprenden las comunicaciones ópticas, redes neuronales, LiDAR, computación, cuántica, entre otros. Las prestaciones clave en las que se pretende dar un salto disruptivo son el tamaño y capacidad para una alta densidad de integración, el consumo de potencia, y el ancho de banda. / [CA] La recerca de noves solucions i idees innovadores al camp de la fotònica de silici mitjançant la integració de nous materials amb prestacions úniques és un tema d'alta actualitat entre la comunitat científica en fotònica i amb un impacte potencial molt alt. D'aquesta temàtica, aquesta tesi pretén contribuir cap a una nova generació de dispositius fotònics basats en la integració d'òxids metàl·lics en tecnologia de silici. Els òxids metàl·lics elegits pertanyen a la família d'òxids conductors transparents (TCO), concretament l'òxid d'indi i estany (ITO) i l'òxid de cadmi (CdO), i materials de canvi de fase (PCM) com el diòxid de vanadi (VO2). Aquests materials es caracteritzen especialment per una variació dràstica de les propietats optoelectròniques, com ara la resistivitat o l'índex de refracció, davant d'un estímul extern ja siga en forma de temperatura, aplicació d'un camp elèctric o excitació òptica. D'aquesta manera, el nostre objectiu és dissenyar, fabricar i demostrar experimentalment noves solucions i dispositius clau com ara dispositius no volàtils, desfasadors i dispositius amb no-linealitat òptica. Aquests dispositius podrien trobar potencial utilitat en diverses aplicacions que comprenen les comunicacions òptiques, xarxes neuronals, LiDAR, computació, quàntica, entre d'altres. Les prestacions clau en què es pretén fer un salt disruptiu són la grandària i la capacitat per a una alta densitat d'integració, el consum de potència i l'amplada de banda. / [EN] The search for new solutions and innovative ideas in the field of silicon photonics through the integration of new materials featuring unique optoelectronic properties is a hot topic among the photonics scientific community with a very high potential impact. Within this topic, this thesis aims to contribute to a new generation of photonic devices based on the integration of metal oxides in silicon technology. The chosen metal oxides belong to the family of transparent conducting oxides (TCOs), namely indium tin oxide (ITO) and cadmium oxide (CdO), and phase change materials (PCMs) such as vanadium dioxide (VO2). These materials are characterized by a drastic variation of their optoelectronic properties, such as resistivity or refractive index, in response to an external stimulus either in the form of temperature, application of an electric field, or optical excitation. Therefore, our objective is to design, fabricate and experimentally demonstrate new solutions and key devices such as non-volatile devices, phase shifters, and devices with optical nonlinearity. Such devices could find potential utility in several applications, including optical communications, neural networks, LiDAR, computing, and quantum. The key features in which we aim to take a leapfrog are footprint and capacity for high integration density, power consumption, and bandwidth. / This work is supported in part by grants ACIF/2018/172 funded by Generaliltat Valenciana, and FPU17/04224 funded by MCIN/AEI/10.13039/501100011033 and by “ESF Investing in your future”. / Parra Gómez, J. (2022). Toward a new generation of photonic devices based on the integration of metal oxides in silicon technology [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/190883