abstract: This thesis work mainly examined the stability and reliability issues of amorphous Indium Gallium Zinc Oxide (a-IGZO) thin film transistors under bias-illumination stress. Amorphous hydrogenated silicon has been the dominating material used in thin film transistors as a channel layer. However with the advent of modern high performance display technologies, it is required to have devices with better current carrying capability and better reproducibility. This brings the idea of new material for channel layer of these devices. Researchers have tried poly silicon materials, organic materials and amorphous mixed oxide materials as a replacement to conventional amorphous silicon layer. Due to its low price and easy manufacturing process, amorphous mixed oxide thin film transistors have become a viable option to replace the conventional ones in order to achieve high performance display circuits. But with new materials emerging, comes the challenge of reliability and stability issues associated with it. Performance measurement under bias stress and bias-illumination stress have been reported previously. This work proposes novel post processing low temperature long time annealing in optimum ambient in order to annihilate or reduce the defects and vacancies associated with amorphous material which lead to the instability or even the failure of the devices. Thin film transistors of a-IGZO has been tested for standalone illumination stress and bias-illumination stress before and after annealing. HP 4155B semiconductor parameter analyzer has been used to stress the devices and measure the output characteristics and transfer characteristics of the devices. Extra attention has been given about the effect of forming gas annealing on a-IGZO thin film. a-IGZO thin film deposited on silicon substrate has been tested for resistivity, mobility and carrier concentration before and after annealing in various ambient. Elastic Recoil Detection has been performed on the films to measure the amount of hydrogen atoms present in the film. Moreover, the circuit parameters of the thin film transistors has been extracted to verify the physical phenomenon responsible for the instability and failure of the devices. Parameters like channel resistance, carrier mobility, power factor has been extracted and variation of these parameters has been observed before and after the stress. / Dissertation/Thesis / M.S. Electrical Engineering 2013

abstract: Microwave (MW), thermal, and ultraviolet (UV) annealing were used to explore the response of Ag structures on a Ge-Se chalcogenide glass (ChG) thin film as flexible radiation sensors, and Te-Ti chalcogenide thin films as a material for diffusion barriers in microelectronics devices and processing of metallized Cu. Flexible resistive radiation sensors consisting of Ag electrodes on a Ge20Se80 ChG thin film and polyethylene naphthalate substrate were exposed to UV radiation. The sensors were mounted on PVC tubes of varying radii to induce bending strains and annealed under ambient conditions up to 150 oC. Initial sensor resistance was measured to be ~1012 Ω; after exposure to UV radiation, the resistance was ~104 Ω. Bending strain and low temperature annealing had no significant effect on the resistance of the sensors. Samples of Cu on Te-Ti thin films were annealed in vacuum for up to 30 minutes and were stable up to 500 oC as revealed using Rutherford backscattering spectrometry (RBS) and four-point-probe analysis. X-ray diffractometry (XRD) indicates Cu grain growth up to 500 oC and phase instability of the Te-Ti barrier at 600 oC. MW processing was performed in a 2.45-GHz microwave cavity on Cu/Te-Ti films for up to 30 seconds to induce oxide growth. Using a calibrated pyrometer above the sample, the temperature of the MW process was measured to be below a maximum of 186 oC. Four-point-probe analysis shows an increase in resistance with an increase in MW time. XRD indicates growth of CuO on the sample surface. RBS suggests oxidation throughout the Te-Ti film. Additional samples were exposed to 907 J/cm2 UV radiation in order to ensure other possible electromagnetically induced mechanisms were not active. There were no changes observed using XRD, RBS or four point probing. / Dissertation/Thesis / M.S. Materials Science and Engineering 2013

abstract: As crystalline silicon solar cells continue to get thinner, the recombination of carriers at the surfaces of the cell plays an ever-important role in controlling the cell efficiency. One tool to minimize surface recombination is field effect passivation from the charges present in the thin films applied on the cell surfaces. The focus of this work is to understand the properties of charges present in the SiNx films and then to develop a mechanism to manipulate the polarity of charges to either negative or positive based on the end-application. Specific silicon-nitrogen dangling bonds (·Si-N), known as K center defects, are the primary charge trapping defects present in the SiNx films. A custom built corona charging tool was used to externally inject positive or negative charges in the SiNx film. Detailed Capacitance-Voltage (C-V) measurements taken on corona charged SiNx samples confirmed the presence of a net positive or negative charge density, as high as +/- 8 x 1012 cm-2, present in the SiNx film. High-energy (~ 4.9 eV) UV radiation was used to control and neutralize the charges in the SiNx films. Electron-Spin-Resonance (ESR) technique was used to detect and quantify the density of neutral K0 defects that are paramagnetically active. The density of the neutral K0 defects increased after UV treatment and decreased after high temperature annealing and charging treatments. Etch-back C-V measurements on SiNx films showed that the K centers are spread throughout the bulk of the SiNx film and not just near the SiNx-Si interface. It was also shown that the negative injected charges in the SiNx film were stable and present even after 1 year under indoor room-temperature conditions. Lastly, a stack of SiO2/SiNx dielectric layers applicable to standard commercial solar cells was developed using a low temperature (< 400 °C) PECVD process. Excellent surface passivation on FZ and CZ Si substrates for both n- and p-type samples was achieved by manipulating and controlling the charge in SiNx films. / Dissertation/Thesis / Ph.D. Electrical Engineering 2013

abstract: Thiol functionalization is one potentially useful way to tailor physical and chemical properties of graphene oxides (GOs) and reduced graphene oxides (RGOs). Despite the ubiquitous presence of thiol functional groups in diverse chemical systems, efficient thiol functionalization has been challenging for GOs and RGOs, or for carbonaceous materials in general. In this work, thionation of GOs has been achieved in high yield through two new methods that also allow concomitant chemical reduction/thermal reduction of GOs; a solid-gas metathetical reaction method with boron sulfides (BxSy) gases and a solvothermal reaction method employing phosphorus decasulfide (P4S10). The thionation products, called "mercapto reduced graphene oxides (m-RGOs)", were characterized by employing X-ray photoelectron spectroscopy, powder X-ray diffraction, UV-Vis spectroscopy, FT-IR spectroscopy, Raman spectroscopy, electron probe analysis, scanning electron microscopy, (scanning) transmission electron microscopy, nano secondary ion mass spectrometry, Ellman assay and atomic force microscopy. The excellent dispersibility of m-RGOs in various solvents including alcohols has allowed fabrication of thin films of m-RGOs. Deposition of m-RGOs on gold substrates was achieved through solution deposition and the m-RGOs were homogeneously distributed on gold surface shown by atomic force microscopy. Langmuir-Blodgett (LB) films of m-RGOs were obtained by transferring their Langmuir films, formed by simple drop casting of m-RGOs dispersion on water surface, onto various substrates including gold, glass and indium tin oxide. The m-RGO LB films showed low sheet resistances down to about 500 k&#937;/sq at 92% optical transparency. The successful results make m-RGOs promising for applications in transparent conductive coatings, biosensing, etc. / Dissertation/Thesis / Ph.D. Chemistry 2013

abstract: Due to diminishing availability of 3He, which is the critical component of neutron detecting proportional counters, large area flexible arrays are being considered as a potential replacement for neutron detection. A large area flexible array, utilizing semiconductors for both charged particle detection and pixel readout, ensures a large detection surface area in a light weight rugged form. Such a neutron detector could be suitable for deployment at ports of entry. The specific approach used in this research, uses a neutron converter layer which captures incident thermal neutrons, and then emits ionizing charged particles. These ionizing particles cause electron-hole pair generation within a single pixel's integrated sensing diode. The resulting charge is then amplified via a low-noise amplifier. This document begins by discussing the current state of the art in neutron detection and the associated challenges. Then, for the purpose of resolving some of these issues, recent design and modeling efforts towards developing an improved neutron detection system are described. Also presented is a low-noise active pixel sensor (APS) design capable of being implemented in low temperature indium gallium zinc oxide (InGaZnO) or amorphous silicon (a-Si:H) thin film transistor process compatible with plastic substrates. The low gain and limited scalability of this design are improved upon by implementing a new multi-stage self-resetting APS. For each APS design, successful radiation measurements are also presented using PiN diodes for charged particle detection. Next, detection array readout methodologies are modeled and analyzed, and use of a matched filter readout circuit is described as well. Finally, this document discusses detection diode integration with the designed TFT-based APSs. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2014

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / The growing interest in the use of new materials and their applications for photovoltaic systems has been a constant concern of the scientific community in recent years. This work is primarily engaged in the collection, characterization and photoactivity testing photovoltaic solar cells made of thin SnO2 doped fluoride films, the films were deposited by the technique of "spray-pyrolysis" and the Sol-Gel method in substrate glass. In glasses microscopy work with dimensions of 2.5 x 7.5 x 1 mm are used as matrices for the conductive substrates or transparent conductive oxides (TCO). These glasses have electrical resistance and transmittance adequate for the manufacture of photoelectrochemical solar cells activated by dyes. Besides making the glasses must be made conductive depositing a layer of titanium oxide, preparation of electrolyte, dye, assembly and characterization of the cells. The conductive substrate has a film of tin dioxide doped with fluorine (SnO2: F), the deposition is made with the aid of a compressor and a spray gun on the glass at a temperature of 600 C from a solution made by the method Sol- gel (MSG). As characterization techniques were used: x-ray diffraction (EDX), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), UV-Vis and Van der Pauw method. The conductive glass has transmittance of 80% (400 nm - 800 nm). The cell with mesoporphyrin dye has Vac = 0.34V and Icc ~ 150&#956;A. The experimental results obtained from these cells may contribute to the development of prototypes that can be used commercially in the capture of solar energy and its consequent transformation into electricity. / O crescente interesse no uso de novos materiais e suas aplicaÃÃes, para sistemas fotovoltaicos tem sido uma constante preocupaÃÃo da comunidade cientifica nos Ãltimos anos. O presente trabalho tem por objetivo principal a obtenÃÃo, caracterizaÃÃo e testes de fotoatividade de cÃlulas solares fotovoltaicas constituÃdas de filmes finos de SnO2 dopados com flÃor, os filmes foram depositados pela tÃcnica de âspray-pirÃliseâ e pelo mÃtodo Sol-Gel em substrato de vidro. Neste trabalho vidros de microscopia com dimensÃo de 2,5 x 7,5 cm x 1 mm, sÃo usados como matrizes para os substratos condutores ou Ãxidos condutores transparentes (OCTâs). Estes vidros possuem resistÃncia elÃtrica e transmitÃncia adequadas para confecÃÃo de cÃlulas solares fotoeletroquÃmicas ativadas por corantes. AlÃm de tornar os vidros condutores deve ser feita a deposiÃÃo de uma camada de Ãxido de titÃnio, preparaÃÃo de eletrÃlito, corante, montagem e caracterizaÃÃo das cÃlulas. O substrato condutor possui um filme de diÃxido de estanho dopado com flÃor (SnO2:F), a deposiÃÃo à feita com o auxilio de um compressor e uma pistola aerogrÃfica sobre o vidro à temperatura de 600ÂC a partir de uma soluÃÃo feita pelo mÃtodo Sol-Gel (MSG). Como tÃcnicas de caracterizaÃÃo foram usadas: difraÃÃo de raios-x (EDX), microscopia eletrÃnica de varredura (MEV), espectroscopia de energia dispersiva (EDS), Uv-Vis e mÃtodo de Van der Pauw. O vidro condutor apresenta transmitÃncia 80% (400 nm â 800 nm ). A cÃlula com corante mesoporfirina apresenta Vca = 0,34 V e Icc ~ 150&#956;A. Os resultados experimentais obtidos dessas cÃlulas poderÃo contribuir para o desenvolvimento de protÃtipos que possam ser utilizados comercialmente na captaÃÃo de energia solar e sua conseqÃente transformaÃÃo em energia elÃtrica.

Visando determinar os valores ótimos para o processo de serramento de anéis bobinados de filme metalizado ultrafino de alumínio com dielétrico de poliéster a partir das condições atuais do processo de fabricação de capacitores pela empresa Epcos do Brasil, realizou-se a avaliação de diferentes tipos de serras circulares variando-se a velocidade de rotação (n) e o tempo de corte (tc). Desenvolvido projeto de experimento desses três fatores a fim de obter o resultado das interações entre eles quanto à resistência de isolamento (Riso) das peças cortadas. A serra de 160 dentes de metal-duro com revestimento de filme de carbono tipo diamante (DLC) apresentou os melhores resultados quanto à “Riso” acima de 0,378 G e quanto ao número de peças com valor abaixo deste. Constatou-se que “n” não influencia significativamente para a distribuição de “Riso”; porém, gera menos peças abaixo do especificado. Já “tc” não influencia significativamente o processo. Quanto ao tipo de dente, o perfil reto obteve melhor resultado para lâminas de serra com 80 dentes e perfil curvo para lâminas com 160 dentes. Já a espessura da lâmina não influenciou de forma expressiva o processo. A lâmina de aço-rápido apresentou adesão de alumínio na lateral do corpo da serra e, consequentemente, adesão de material na superfície de corte. As lâminas de metal-duro sem revestimento apresentaram falhas no filme metalizado por causa do atrito gerado entre a superfície de corte e a lateral da lâmina; esse inconveniente é eliminado quando ela é revestida com filme DLC apresentando melhorias quanto à “Riso” das peças para “n” menores. Também houve adesão de alumínio na parte inferior do dente devido a uma delaminação da camada de filme DLC. / In order to determine the optimal values for the sawing process of wound rings of metalized ultra-thin film with dielectric of polyester from current conditions of capacitor manufacturing process by Epcos company in Brazil, it was performed the evaluation of different types of circular saws varying the rotational speed (n) and the cutting time (tc). Developed experiment design methodology for these three factors in order to get the result of the interactions between them regarding to the insulation resistance (Riso) of cut parts. Through the analysis of the main effects, the cemented carbide saw with 160 teeth and diamond-like carbon (DLC) film coating showed the best results in terms of "Riso" above 0,378 G and regarding to the number of parts with value below the specified. It was found that "n" does not influence significantly the distribution of "Riso"; however, generates fewer parts below the specified. Now "tc" does not significantly influence the process. Regarding the tooth type, straight profile obtained better results for saw blades with 80 teeth and curved profile for blades with 160 teeth. However the thickness of the blade did not influence significantly the process. The high speed steel blade presented adhesion of aluminum on the side of the saw body and, consequently, adhesion of material on the cutting surface. The cemented carbide blades uncoated presented failures on metalized film because of the friction generated between the cutting surface and the side of the blade; this drawback is eliminated when it is coated with DLC film presenting improvements to the parts "Riso" for lower "n". There was also aluminum adhesion on the bottom of the tooth due to a delamination of the DLC film layer.

Este trabalho apresenta a produção e a caracterização de filmes finos produzidos a partir da técnica de RF Magnetron Sputtering. Foram produzidos filmes finos sobre substrato de silício a partir de alvos vítreos de germânio de GeO2-PbO preparados com e sem os reagentes AgNO3 e Cu2O. Foi desenvolvida metodologia adequada para a obtenção de nanopartículas em filmes finos por meio de tratamento térmico. Os filmes foram caracterizados por técnicas de perfilometria, elipsometria, Microscopia de Força Atômica (AFM), Rutherford Backscattering (RBS), Microscopia Eletrônica de Transmissão (TEM) e medidas elétricas para a obtenção das curvas de capacitância e corrente em função da tensão. Os valores dos índices de refração medidos ficaram em torno de 1,9, isto é, próximo do valor do alvo vítreo utilizado para as deposições. Através do AFM foi observado que a rugosidade vale-pico variou de 2 a 4 nm. Através de TEM verificou-se em todos os filmes a presença de nanopartículas metálicas e também facetas cristalinas formadas pelos próprios elementos da matriz. Pelas medidas elétricas, foram obtidos os resultados das constantes dielétricas que variaram com o tratamento térmico. Os valores variaram de 8 a 15 superando o valor do SiO2 que é de 3,9. Com todos os resultados elétricos, foi notado que o filme preparado com o reagente CU2O foi o que apresentou maior estabilidade com o tratamento térmico o que é adequado para o preparo de dispositivos MOS. Neste caso o valor obtido para a constante dielétrica foi de 14. / This work presents the production and characterization of thin films produced by the RF Magnetron Sputtering technique. There were produced thin films on silicon substrate from vitreous targets of GeO2-PbO prepared with and without AgNO3 and Cu2O reagents. It was developed adequate methodology to obtain metallic nanoparticles in thin films by means of heat treatment. The films were characterized using perfilomitry, ellipsometry, Atomic Force Microscopy (AFM), Rutherford Backscattering (RBS), Transmission Electron Microscopy (TEM) techniques and electrical measurements in order to obtain the curves of current and capacitance as a function of the voltage. The values of refractive indices were measured around 1.9 next to the value of the vitreous target used for the deposition. Through the AFM, it was observed that the valley-peak roughness varied from 2 to 4 nm. Through TEM, it was observed in all films the presence of metallic nanoparticles and also some crystalline faces formed by the elements of the matrix. With the electrical measurements, there were obtained the dielectric constants that varied with the heat treatment. The values ranged from 8 to 15 surpassing the value of SiO2 which is 3.9. With all the electric results, it was noted that the film prepared with copper was the one that presented the highest stability with the heat treatment that is appropriate for the preparation of MOS devices.

Orientador: Jose Alexandre Diniz / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e Computação / Made available in DSpace on 2018-08-12T04:29:31Z (GMT). No. of bitstreams: 1 Barros_AngelicaDenardide_M.pdf: 3382435 bytes, checksum: 06e6858052deff3336f5e44a60b55e08 (MD5) Previous issue date: 2008 / Resumo: O presente trabalho tem como objetivo a caracterização de filmes finos de óxido de titânio para aplicação em transistores de efeito de campo sensíveis a íons, do inglês ion sensitive field effect transistors (ISFETs). Para isso, filmes finos de titânio de diferentes espessuras foram depositados através de uma evaporadora por feixe de elétrons sobre substrato de silício. Posteriormente, estes filmes foram oxidados e recozidos utilizando diferentes temperaturas através de um forno de processamento térmico rápido, do inglês rapid thermal process (RTP). Os filmes de óxido de titânio (TiOx) foram então caracterizados de forma estrutural através das técnicas Elipsometria, Espectroscopia Infravermelho, Espectroscopia RAMAN, Microscopia de Força Atômica e Espectroscopia de Retroespalhamento Rutheford. Dependendo da temperatura do patamar de tratamento térmico, foram obtidos filmes com diferentes concentrações de oxigênio, o que influenciou na espessura final, no índice de refração, na rugosidade da superfície e nos contornos de grão da superfície dos filmes. Através da caracterização estrutural foi possível verificar a formação de filmes de TiOx compostos principalmente da estrutura cristalina rutilo do TiO2, mas que também apresentaram a estrutura cristalina anatase, além da formação de uma fina camada de Ti2O3 e SiO2 entre o substrato de silício e o filme de TiOx. A caracterização elétrica realizada através da análise das curvas I-V e C-V, obtidas a partir de capacitores confeccionados através da deposição de eletrodos de aluminio (Al/Si/TiOx/Al), demostraram a obtenção de dielétricos de boa qualidade com valores de constante dielétrica entre 12 e 33, densidade de carga na interface da ordem de 1010/cm2 e densidade de corrente de fuga entre 1 e 10-4 A/cm2. Transistores de efeito de campo foram confeccionados para a obtenção de curvas IDxVDS e log IDxTensão. Foi encontrado valor de tensão de Early igual a -1629V, resistência de saída, ROUT, igual a 215MO e slope de 100mV/dec para o dielétrico de TiOx obtido com tratamento térmico em 960°C. O filme de TiOx tratado térmicamente em 600°C foi testado como sensor através de medidas C-V adaptadas e apresentou deslocamento da VFB em função da variação do pH da solução testada, apresentando potencial como sensor de pH. / Abstract: This work presents the characterization of thin titanium oxide films as potential dielectric to be applied in ion sensitive field effect transistors. The films were obtained through rapid thermal oxidation and annealing of titanium thin films of different thicknesses deposited by Ebeam evaporation on silicon wafers. These films were analyzed by Ellipsometry, Infrared Spectroscopy, Raman Spectroscopy, Atomic Force Microscopy and Rutherford Backscattering Spectroscopy. The final thicknesses of the thin films, roughness, surface grain countors, refractive indexes and oxigen concentration depend on the oxidation and annealing temperature. Structural characterization showed the presence of other oxides such Ti2O3, an interfacial SiO2 layer between the dielectric and the substrate and the anatase crystalline phase of TiO2 films besides the mainly found crystalline phase rutile. Electrical characterizations were obtained through I-V and C-V curves of Al/Si/TiOx/Al capacitors. These curves showed that the films had high dielectric constants between 12 and 33, interface charge density about 1010/cm2 and leakage current density about 1 and 10-4 A/cm2. Field effect transistors were made in order to analyze IDxVDS and log IDxBias curves. Early tension value of -1629V, ROUT value of 215MO and slope of 100mV/dec were calculated for the TiOx thin film thermally treated with 960°C. The TiOx thin film thermally treated with 600°C was successfully tested as pH sensor through adapted C-V measurements, which showed shifts in the VFB according to the H+ concentration in tested solutions. / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

La ptychographie est une technique d’imagerie par diffraction cohérente qui vise à récupérer la phase perdue, uniquement par des mesures d’intensité en champ lointain. Cette technique permet l’imagerie des champs de déformation dans des cristaux périodiques avec des résolutions sous-faisceau. Dans ce travail, la ptychographie de Bragg en 3D est utilisée pour étudier les propriétés d’une couche cristalline nanostructurée de InP/InGaAs collée sur un substrat de silicium. L’expérience a été réalisée sur la ligne ID13 de l’ESRF, avec un faisceau monochromatique concentré à 100nm. Les intensités 2D ont été acquises avec plusieurs angles d’incidence dans le voisinage du pic de Bragg InP (004), empilant un jeu de données tridimensionnelles. L’analyse numérique du problème donné a été effectuée à l’avance afin d’optimiser la stratégie d’inversion et d’étudier la possibilité d’introduire des contraintes physiques supplémentaires basées sur des approches de régularisation. L’inversion de l’ensemble des données a été effectuée en utilisant un algorithme ptychographique de reconstruction de phase. L’image 3D récupérée représente la haute qualité cristalline de l’échantillon, avec les valeurs de l’épaisseur et du désaccord de maille attendus en moyenne. Néanmoins, de petites inclinaisons locales de mailles ont été observées - de l’ordre de 0.02°- et confirmées par modélisation numérique. Les résultats démontrent la sensibilité de la technique, ainsi que ses perspectives passionnantes pour l’imagerie des matériaux organiques et inorganiques nanostructurés complexes. / Ptychography is a coherent diffraction imaging technique which aims in retrieving the lost phase from intensity-only far-field measurements. The versatility of the approach has proved an important asset for 3D mapping of different physical quantities, like the electron density of micrometer-sized specimens with resolution in the 10 - 100nm range. In this work, we explored the possibility to push further the current limits of 3D Bragg ptychography, by addressing the case of an extended InP/InGaAs nanostructured thin film, bonded on a silicon wafer. The experiment was performed at the ID13 beamline at ESRF, with a monochromatic beam focused down to 100nm. 2D intensity patterns were acquired at several incidence angles in the vicinity of the InP (004) Bragg peak, stacking up a three dimensional dataset. Numerical analysis of the given problem was performed beforehand in order to optimize the inversion strategy and study the possibility of introducing additional physical constraints through regularization approaches. Inversions of the dataset were done using a ptychographical gradient-based optimization phase retrieval algorithm. The developed strategy was applied on the experimental data which led to the retrieval of a complex-valued 3D image. The result exhibits the high crystallinity quality of the sample with the expected values of thickness and lattice mismatch, nevertheless, small local lattice tilts have been observed - in the order of 0.02°- and confirmed by numerical modeling. This result demonstrates the high sensitivity of the technique, as well as its exciting perspectives for imaging complex organic and inorganic nanostructured materials.