Neste trabalho foi desenvolvido um estudo sistemático dos mecanismos de difusão responsáveis pelo switching de resistência em memórias resistivas. Essas memórias possuem estrutura semelhante a de um capacitor, a qual sofre uma transição de resistência induzida pela aplicação de um campo elétrico. A transição é provocada pela formação de filamentos condutivos no interior da matriz semicondutora. Os filamentos podem ser constituídos por metal originado de um dos eletrodos (ECM) ou por regiões do óxido deficientes em oxigênio (VCM), geradas pela difusão de vacâncias de oxigênio. Dispositivos de TiO2 foram construídos e sua resposta elétrica foi adquirida através de medidas elétricas do tipo I-V para diferentes metais de eletrodo. Técnicas de análise por feixe de íons, como retroespalhamento Rutherford por micro-feixe e perfilometria com reação nuclear ressonante, foram usadas para detalhamento dos processos de difusão. Constatou-se uma dependência do comportamento elétrico em função do método de deposição da camada semicondutora, sua espessura e os parâmetros da medida de tensão. No caso do filamento ser composto por átomos de metal, espectros de micro-RBS foram adquiridos para identificar a sua estrutura no interior do óxido. Ainda, observaram-se bolhas na superfície do eletrodo superior dos dispositivos com difusão de vacâncias de oxigênio após o tratamento elétrico. Nesse mesmo contexto, foi medida a difusividade e energia de ativação da difusão de oxigênio em filmes finos de TiOy. / In this work we developed a systematic study of diffusion mechanisms which are responsible for resistance switching in resistive memories. The structure of these memories is similar to a capacitor which suffers resistance transition induced by electrical field. The transition is caused by the formation of conductive filaments inside the semiconductor matrix. The filaments may be constituted by metal from one of the electrodes (ECM) or by oxygen deficient areas (VCM), generated from oxygen vacancies diffusion. Devices of TiO2 have been built and its electrical response was acquired through electrical measurements (I-V) for different electrode metals. Ion beam techniques such as micro-probe Rutherford Backscattering and Nuclear Reaction Profiling were used to detail the diffusion processes. It was observed a dependence in the electrical behaviour with the semiconductor layer deposition method, its thickness and bias measurement parameters. In the case which filaments are composed by metal atoms, measurements of micro-RBS were performed to identify its structure inside the oxide. Also, bubbles have been observed over the surface of top electrode in devices with oxygen vacancies diffusion after the electrical treatment. In this context, it was measured diffusivity and activation energy for oxygen diffusion in thin TiOy films.

Neste trabalho foi desenvolvido um estudo sistemático dos mecanismos de difusão responsáveis pelo switching de resistência em memórias resistivas. Essas memórias possuem estrutura semelhante a de um capacitor, a qual sofre uma transição de resistência induzida pela aplicação de um campo elétrico. A transição é provocada pela formação de filamentos condutivos no interior da matriz semicondutora. Os filamentos podem ser constituídos por metal originado de um dos eletrodos (ECM) ou por regiões do óxido deficientes em oxigênio (VCM), geradas pela difusão de vacâncias de oxigênio. Dispositivos de TiO2 foram construídos e sua resposta elétrica foi adquirida através de medidas elétricas do tipo I-V para diferentes metais de eletrodo. Técnicas de análise por feixe de íons, como retroespalhamento Rutherford por micro-feixe e perfilometria com reação nuclear ressonante, foram usadas para detalhamento dos processos de difusão. Constatou-se uma dependência do comportamento elétrico em função do método de deposição da camada semicondutora, sua espessura e os parâmetros da medida de tensão. No caso do filamento ser composto por átomos de metal, espectros de micro-RBS foram adquiridos para identificar a sua estrutura no interior do óxido. Ainda, observaram-se bolhas na superfície do eletrodo superior dos dispositivos com difusão de vacâncias de oxigênio após o tratamento elétrico. Nesse mesmo contexto, foi medida a difusividade e energia de ativação da difusão de oxigênio em filmes finos de TiOy. / In this work we developed a systematic study of diffusion mechanisms which are responsible for resistance switching in resistive memories. The structure of these memories is similar to a capacitor which suffers resistance transition induced by electrical field. The transition is caused by the formation of conductive filaments inside the semiconductor matrix. The filaments may be constituted by metal from one of the electrodes (ECM) or by oxygen deficient areas (VCM), generated from oxygen vacancies diffusion. Devices of TiO2 have been built and its electrical response was acquired through electrical measurements (I-V) for different electrode metals. Ion beam techniques such as micro-probe Rutherford Backscattering and Nuclear Reaction Profiling were used to detail the diffusion processes. It was observed a dependence in the electrical behaviour with the semiconductor layer deposition method, its thickness and bias measurement parameters. In the case which filaments are composed by metal atoms, measurements of micro-RBS were performed to identify its structure inside the oxide. Also, bubbles have been observed over the surface of top electrode in devices with oxygen vacancies diffusion after the electrical treatment. In this context, it was measured diffusivity and activation energy for oxygen diffusion in thin TiOy films.

Orientador: Newton Cesário Frateschi / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-15T03:39:57Z (GMT). No. of bitstreams: 1 SilvaFilho_Adenirda_D.pdf: 7071967 bytes, checksum: 323c5d4f6939473d571146b5d6531fda (MD5) Previous issue date: 2010 / Resumo: Este trabalho apresenta o uso de cavidades ressonantes baseadas em geometrias de bilhares caóticos construídas em meios semicondutores opticamente ativos, visando seu aproveitamento ao sensoriamento. Apesar do comportamento clássico caótico do estádio, a descrição quântica, no limite semiclássico, mostra inesperados acúmulos de densidade de probabilidade sobre muitas trajetórias periódicas fechadas, chamadas cicatrizes. A literatura mostra que o espaço físico das trajetórias relacionadas a cada cicatriz pode ser obtido pela soma da densidade de probabilidade de auto-estados na vizinhança de cada cicatriz. Classicamente, as trajetórias ligadas a cada auto-estado possuem órbitas muito próximas devido a sua instabilidade, e quando misturadas, definem uma órbita de largura não nula. No domínio óptico, isomórfico ao problema quântico descrito acima, as trajetórias vêm de um tratamento de traçado de raios e os auto-estados são os modos eletromagnéticos estacionários. Particularmente, no caso da cavidade dielétrica, o sistema é aberto, uma vez que a luz pode ser transmitida para fora do ressonador. Desta forma, há grande mistura dos modos e uma seleção maior daqueles que podem sobreviver por terem trajetórias com ângulos internos de incidência maiores que o ângulo crítico para reflexão total interna. Em uma trajetória fechada e curta, modos estacionários são definidos e essas trajetórias têm maior probabilidade de serem observadas, em relação a outras possíveis. Quando o ressonador é constituído por um meio ativo opticamente, este confinamento realiza a realimentação óptica do sistema, cujo ganho óptico permite o estabelecimento estável e coerente de tais trajetórias. Estes resultados inspiraram a realização deste trabalho, cuja grande motivação foi investigar o processo de seleção modal e aplicá-lo em dispositivos práticos para sensoriamento em pequenos volumes. Experimentalmente foi desenvolvida uma técnica híbrida de fabricação utilizando um sistema de íons focalizados (FIB) juntamente com técnicas de microfabricação convencionais para a produção de cavidades estádio com meio ativo de poços quânticos de InGaAsP. Finalmente, foram obtidos resultados da emissão espectral com grande concordância com a previsão teórica baseada numa abordagem matemática simples de soma incoerente de cicatrizes. A seleção modal foi demonstrada com a alteração da excentricidade e com a inserção de furos sobre as trajetórias. A aplicação ao sensoriamento foi explorada tanto pela observação do espectro de emissão quanto pela detecção de fotocorrente por estádios emissor e detector integrados. Variações de até 80% de fotocorrente e alterações significativas do espectro foram observadas para detecção de isopropanol e água. Estes resultados mostram possibilidades de sensoriamento prático utilizando os estádios / Abstract: This work presents the development of resonant cavities based on chaotic billiard geometries built with semiconductor active optical medium for sensing applications. In spite of the classically chaotic behavior of the stadium, the quantum description of the problem in the semi-classical limit shows unexpected accumulations of the density of probability on closed periodic paths called scars. The literature shows that the physical space of the paths related to a given scar can be obtained by adding several eigen-states neighboring each scar. Classically, the paths connected to each eigen-state have very close orbits due to their instability which, when mixed, define a non-zero width orbit. In the optical domain, isomorphic to the quantum problem described above, the paths are a result of the ray treatment and the eigen-modes are the stationary electromagnetic modes. Particularly, in the case of a dielectric cavity, the system is open for light can escape the resonator. Therefore, there is a great mixture of modes and a strong selection of modes with paths with incidence angle below the critical angle. In a closed and short path, stationary modes are defined and those paths have larger probability of observation. When the resonator has an optically active medium, the confinement provides optical feedback to the system which with optical gain allows the establishment of coherent and stable scars. These results inspired this work where the process of modal selection was investigated and applied for sensing in small volumes. Experimentally, a hybrid fabrication approach based on Focused Ion Beam (FIB) and conventional micro-fabrication techniques was used to produce stadium optical cavities with InGaAsP quantum well active region. Finally, we obtained the spectral emission of the devices with good agreement with our simulation based on a simple mathematical approach employing the incoherent summation of the scars. The modal selection with the modification of the eccentricity of the cavity and with the insertion of holes along the scars was demonstrated. The application to sensing was explored by the observation of the emission spectrum as well as by measured photo-current on detection between stadia emitter and detector integrated. Photo-current variations of up to 80% and significant changes of the emission spectrum were observed for isopropanol and water detection. These results show possibilities of practical sensing by stadiums / Doutorado / Física / Doutor em Ciências

M.Sc. / Layered Manufacturing (LM), also known as "Rapid Prototyping", is that process in terms of which a computer-designed model is created layer by layer with the aid of specific LM hardware. Telemanufacturing constitutes an extension of this technology that allows remote submission of manufacturing jobs or assignments across a communication medium, typically the Internet, to be built at the manufacturing bureau concerned. The de facto standard of LM is the STL file. Simply put, this file consists of a number of triangles that are used to describe an object in its entirety. This file format has several advantages over other known formats and allows easy 2D rendering. Unfortunately, however, the limitations of the latter format outweigh its advantages. Since the entire model is described in terms of a collection of triangles, the original geometry of the model is lost. As a result, a certain level of degradation will occur, especially around curvatures in the model. Although an increase in the number of triangles around such areas will enhance precision, it will also result in a much larger STL file. Triangles that get lost somewhere inside the file could also give rise to holes, orphaned surfaces and zero-width walls in the projected object. It is vital, therefore, that the manufacturing bureau verify the correctness of the entire file before it is built in order to prevent machine time and materials from being wasted. Instead of transmitting the entire file again, the bureau could attempt automatically to correct and repair less critical errors, thereby saving valuable resources and time.

The purpouse of the master's thesis is study problematic of focused ion beams and their material influence. In this thesis are described interactions in the sample after impact of ion beam, use and applications of FIB systems. Second part of thesis are simulations of ion influence on different kinds of materials by the help of SRIM program.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21555号 / 理博第4462号 / 新制||理||1640(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 前野 悦輝, 教授 石田 憲二, 教授 寺嶋 孝仁 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Předložená diplomová práce se zabývá implementací metody rentgenové emisne indukované částicemi do experimentálního uspořádání za účelem doplnění rodiny metod založených na iontových technikách, tj. Rutherfordovy zpětné rozptylové spektrometrie, spektrometrie elastického zpětného rozptylu a analýzy detekce doby letu/energie elastického odrazu. Výhoda více-metodického přístupu je demonstrována na vrstvách ze slitin přechodných kovů obsahujících lehké prvky, kde samo-konzistentní analýza poskytuje výrazně zlepšené a přesné informace o stechiometrii, hloubkovém rozložení a tloušťce slitiny. Hmotnostní spektrometrie sekundárních iontů je použita pro porovnání a doplnění získaných výsledků.

This thesis is divided into three main parts dealing with ion beam assisted deposition. In the first part there is a brief description of the IBAD chamber at Institute of Physical Engineering of BUT. There is also a detailed description of control of the IBAD apparatus during deposition. Next part deals with measuring of deposition rates of ion sputtering in order to refine deposition of thin layers. Last part deals with planned and already finished changes that should improve quality and speed of thin layers deposition. Changes include the option of covering the substrate holder, change of the entry flange, design of new insertion chamber with multifunctional substrate holder and the option to control the deposition by computer.

The aim of this work is fabrication of nanostructures and measurement of their electrotransport properties. There are two different methods used for fabrication - electron beam lithography with sputtering of thin films and focused ion beam with deposition from gas phase. I-V characteristic was measured for characterisation of as prepared nanostructures - wires. Material of wires prepared by using of electron beam lithography was permalloy - an alloy of iron and nickel. Second types of wires prepared by using of chemical vapor deposition induced by focused ion beam was platinum based.

The rapid growth of the microelectronics industry in the last decades made it possible to produce structures in the sub-micrometer scale on silicon chips and to reach an integration scale under 100 nm. Decreasing the size and increasing the complexity of these structures make a control of quality and defects investigation more difficult. During a long time ultrasound devices are being used for nondestructive investigation of materials, like ultrasound microscopes, scanning photo-acoustic microscopes or scanning electron-acoustic microscopes, where acoustic waves are generated by acoustic transducers, focused laser or electron beams, respectively. The aim of this work is to investigate more precisely the acoustic wave generation by pulsed and periodically modulated ion beams in different solid materials depending on the beam parameters and to demonstrate the possibility to apply an intensity modulated focused ion beam (FIB) for acoustic emission and for nondestructive investigation of the internal structure of materials on a microscopic scale. The combination of a FIB and an ultrasound microscope in one device can provide the opportunity of nondestructive investigation, production and modification of micro- and nanostructures simultaneously. The FIB spot size in modern systems is comparable with that of a focused electron beam and the penetration depth of ions with energy of 20-60 keV is lower than 100 nm. This makes it possible to reach a sub-micrometer resolution of a scanning ion acoustic microscope. On the other hand side a FIB with energy of 20-60 keV is a good tool which can be used for the fabrication of nanostructures using ion milling, implantation or ion beam assisted deposition techniques. The bulk ultrasound emission in a solid was investigated using a pulsed high energy ion beam focused on aluminum, copper, iron and silicon samples. Oxygen, silicon and gold ion beams were applied in charge states from 1+ to 4+ with the pulse duration of 0.5 - 4 µs and an energy of 1.5 - 10 MeV. Intensity of the detected acoustic waves shows a linear dependence on the energy of the incident ions, on the ion flux as well as on the pulse duration. No influence of the ion charge and ion mass to the emission of acoustic waves was observed. The ion acoustic effect was applied for a nondestructive material inspection using intensity modulated FIB providing by the IMSA-100 FIB system with an accelerating potential of 30-35 kV. The achieved lateral resolution of this scanning ion acoustic microscope is in the micrometer range depending on the sample material and the beam modulation frequency. The resolution can be improved by increasing the frequency. The maximal modulation frequency which was obtained at IMSA-100 is about 2 MHz corresponding to lateral resolution of 4-5 µm on silicon. Using this microscope, some images of integrated microstructures on a silicon chip were obtained using the lock-in technique for filtering of the signal from the noise and increasing of the total imaging time. The possibility to visualize near sub-surface structure was demonstrated. Due to the strong sputtering effect and the long time of irradiation the imaged structures were significantly damaged. Si2+, Ge2+, Ga+ and Au+ ions were used. All these ions are quite heavy and have high sputtering coefficients. Long-time imaging improves the quality of acoustic images, i. e. the signal-to-noise ratio is reduced with the square root from the pixel time, but leads to significant erosion of the imaged structure.