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.

abstract: Non-volatile memory (NVM) has become a staple in the everyday life of consumers. NVM manifests inside cell phones, laptops, and most recently, wearable tech such as smart watches. NAND Flash has been an excellent solution to conditions requiring fast, compact NVM. Current technology nodes are nearing the physical limits of scaling, preventing flash from improving. To combat the limitations of flash and to appease consumer demand for progressively faster and denser NVM, new technologies are needed. One possible candidate for the replacement of NAND Flash is programmable metallization cells (PMC). PMC are a type of resistive memory, meaning that they do not rely on charge storage to maintain a logic state. Depending on their application, it is possible that devices containing NVM will be exposed to harsh radiation environments. As part of the process for developing a novel memory technology, it is important to characterize the effects irradiation has on the functionality of the devices. This thesis characterizes the effects that ionizing γ-ray irradiation has on the retention of the programmed resistive state of a PMC. The PMC devices tested used Ge30Se70 doped with Ag as the solid electrolyte layer and were fabricated by the thesis author in a Class 100 clean room. Individual device tiles were wire bonded into ceramic packages and tested in a biased and floating contact scenario. The first scenario presented shows that PMC devices are capable of retaining their programmed state up to the maximum exposed total ionizing dose (TID) of 3.1 Mrad(Si). In this first scenario, the contacts of the PMC devices were left floating during exposure. The second scenario tested shows that the PMC devices are capable of retaining their state until the maximum TID of 10.1 Mrad(Si) was reached. The contacts in the second scenario were biased, with a 50 mV read voltage applied to the anode contact. Analysis of the results show that Ge30Se70 PMC are ionizing radiation tolerant and can retain a programmed state to a higher TID than NAND Flash memory. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2015

abstract: This work focuses on the existence of multiple resistance states in a type of emerging non-volatile resistive memory device known commonly as Programmable Metallization Cell (PMC) or Conductive Bridge Random Access Memory (CBRAM), which can be important for applications such as multi-bit memory as well as non-volatile logic and neuromorphic computing. First, experimental data from small signal, quasi-static and pulsed mode electrical characterization of such devices are presented which clearly demonstrate the inherent multi-level resistance programmability property in CBRAM devices. A physics based analytical CBRAM compact model is then presented which simulates the ion-transport dynamics and filamentary growth mechanism that causes resistance change in such devices. Simulation results from the model are fitted to experimental dynamic resistance switching characteristics. The model designed using Verilog-a language is computation-efficient and can be integrated with industry standard circuit simulation tools for design and analysis of hybrid circuits involving both CMOS and CBRAM devices. Three main circuit applications for CBRAM devices are explored in this work. Firstly, the susceptibility of CBRAM memory arrays to single event induced upsets is analyzed via compact model simulation and experimental heavy ion testing data that show possibility of both high resistance to low resistance and low resistance to high resistance transitions due to ion strikes. Next, a non-volatile sense amplifier based flip-flop architecture is proposed which can help make leakage power consumption negligible by allowing complete shutdown of power supply while retaining its output data in CBRAM devices. Reliability and energy consumption of the flip-flop circuit for different CBRAM low resistance levels and supply voltage values are analyzed and compared to CMOS designs. Possible extension of this architecture for threshold logic function computation using the CBRAM devices as re-configurable resistive weights is also discussed. Lastly, Spike timing dependent plasticity (STDP) based gradual resistance change behavior in CBRAM device fabricated in back-end-of-line on a CMOS die containing integrate and fire CMOS neuron circuits is demonstrated for the first time which indicates the feasibility of using CBRAM devices as electronic synapses in spiking neural network hardware implementations for non-Boolean neuromorphic computing. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2015

abstract: Measurements of the geometrical magnetoresistance of a conventional semiconductor, gallium arsenide (GaAs), and a more recently developed semiconductor, iron pyrite (FeS2) were measured in the Corbino disc geometry as a function of magnetic field to determine the carrier mobility (μm). These results were compared with measurements of the Hall mobility (μH) made in the Van der Pauw configuration. The scattering coefficient (ξ), defined as the ratio between magnetoresistance and Hall mobility (μm/μH), was determined experimentally for GaAs and natural pyrite from 300 K to 4.2 K. The effect of contact resistance and heating on the measurement accuracy is discussed. / Dissertation/Thesis / Masters Thesis Materials Science and Engineering 2016

abstract: The Programmable Metallization Cell (PMC) is a novel solid-state resistive switching technology. It has a simple metal-insulator-metal “MIM” structure with one metal being electrochemically active (Cu) and the other one being inert (Pt or W), an insulating film (silica) acts as solid electrolyte for ion transport is sandwiched between these two electrodes. PMC’s resistance can be altered by an external electrical stimulus. The change of resistance is attributed to the formation or dissolution of Cu metal filament(s) within the silica layer which is associated with electrochemical redox reactions and ion transportation. In this dissertation, a comprehensive study of microfabrication method and its impacts on performance of PMC device is demonstrated, gamma-ray total ionizing dose (TID) impacts on device reliability is investigated, and the materials properties of doped/undoped silica switching layers are illuminated by impedance spectroscopy (IS). Due to the inherent CMOS compatibility, Cu-silica PMCs have great potential to be adopted in many emerging technologies, such as non-volatile storage cells and selector cells in ultra-dense 3D crosspoint memories, as well as electronic synapses in brain-inspired neuromorphic computing. Cu-silica PMC device performance for these applications is also assessed in this dissertation. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2017

abstract: High-k dielectrics have been employed in the metal-oxide semiconductor field effect transistors (MOSFETs) since 45 nm technology node. In this MOSFET industry, Moore’s law projects the feature size of MOSFET scales half within every 18 months. Such scaling down theory has not only led to the physical limit of manufacturing but also raised the reliability issues in MOSFETs. After the incorporation of HfO2 based high-k dielectrics, the stacked oxides based gate insulator is facing rather challenging reliability issues due to the vulnerable HfO2 layer, ultra-thin interfacial SiO2 layer, and even messy interface between SiO2 and HfO2. Bias temperature instabilities (BTI), hot channel electrons injections (HCI), stress-induced leakage current (SILC), and time dependent dielectric breakdown (TDDB) are the four most prominent reliability challenges impacting the lifetime of the chips under use. In order to fully understand the origins that could potentially challenge the reliability of the MOSFETs the defects induced aging and breakdown of the high-k dielectrics have been profoundly investigated here. BTI aging has been investigated to be related to charging effects from the bulk oxide traps and generations of Si-H bonds related interface traps. CVS and RVS induced dielectric breakdown studies have been performed and investigated. The breakdown process is regarded to be related to oxygen vacancies generations triggered by hot hole injections from anode. Post breakdown conduction study in the RRAM devices have shown irreversible characteristics of the dielectrics, although the resistance could be switched into high resistance state. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2018

Les nouvelles approches de technologies mémoires permettront une intégration dite back-end, où les cellules élémentaires de stockage seront fabriquées lors des dernières étapes de réalisation à grande échelle du circuit. Ces approches innovantes sont souvent basées sur l'utilisation de matériaux actifs présentant deux états de résistance distincts. Le passage d'un état à l'autre est contrôlé en courant ou en tension donnant lieu à une caractéristique I-V hystérétique. Nos mémoires résistives sont composées d'argent en métal électrochimiquement actif et de sulfure amorphe agissant comme électrolyte. Leur fonctionnement repose sur la formation réversible et la dissolution d'un filament conducteur. Le potentiel d'application de ces nouveaux dispositifs n'est pas limité aux mémoires ultra-haute densité mais aussi aux circuits embarqués. En empilant ces mémoires dans la troisième dimension au niveau des interconnections des circuits logiques CMOS, de nouvelles architectures hybrides et innovantes deviennent possibles. Il serait alors envisageable d'exploiter un fonctionnement à basse énergie, à haute vitesse d'écriture/lecture et de haute performance telles que l'endurance et la rétention. Dans cette thèse, en se concentrant sur les aspects de la technologie de mémoire en vue de développer de nouvelles architectures, l'introduction d'une fonctionnalité non-volatile au niveau logique est démontrée par trois circuits hybrides: commutateurs de routage non volatiles dans un Field Programmable Gate Arrays, un 6T-SRAM non volatile, et les neurones stochastiques pour un réseau neuronal. Pour améliorer les solutions existantes, les limitations de la performances des dispositifs mémoires sont identifiés et résolus avec des nouveaux empilements ou en fournissant des défauts de circuits tolérants. / Novel approaches in the field of memory technology should enable backend integration, where individual storage nodes will be fabricated during the last fabrication steps of the VLSI circuit. In this case, memory operation is often based upon the use of active materials with resistive switching properties. A topology of resistive memory consists of silver as electrochemically active metal and amorphous sulfide acting as electrolyte and relies on the reversible formation and dissolution of a conductive filament. The application potential of these new memories is not limited to stand-alone (ultra-high density), but is also suitable for embedded applications. By stacking these memories in the third dimension at the interconnection level of CMOS logic, new ultra-scalable hybrid architectures becomes possible which exploit low energy operation, fast write/read access and high performance with respect to endurance and retention. In this thesis, focusing on memory technology aspects in view of developing new architectures, the introduction of non-volatile functionality at the logic level is demonstrated through three hybrid (CMOS logic ReRAM devices) circuits: nonvolatile routing switches in a Field Programmable Gate Array, nonvolatile 6T-SRAMs, and stochastic neurons of an hardware neural network. To be competitive or even improve existing solutions, limitations on the memory devices performances are identified and solved by stack engineering of CBRAM devices or providing faults tolerant circuits.

Submitted by leonardo Perinotto abdalla (leoabdalla@live.com) on 2018-03-16T15:22:43Z No. of bitstreams: 1 Dissertação .pdf: 4793508 bytes, checksum: 9e8ed8362972b0fe05f4c6d100e03979 (MD5) / Approved for entry into archive by Ana Paula Santulo Custódio de Medeiros null (asantulo@rc.unesp.br) on 2018-03-16T16:39:16Z (GMT) No. of bitstreams: 1 abdalla_lhp_me_rcla.pdf: 4789566 bytes, checksum: 85a14005b703aa3dd03acc7d79a891de (MD5) / Made available in DSpace on 2018-03-16T16:39:16Z (GMT). No. of bitstreams: 1 abdalla_lhp_me_rcla.pdf: 4789566 bytes, checksum: 85a14005b703aa3dd03acc7d79a891de (MD5) Previous issue date: 2018-02-28 / O objetivo deste estudo foi testar as hipóteses de que o torque critico (TC) (expresso como % de uma contração voluntária máxima, CVM) é maior para os flexores plantares (FP) com relação aos músculos extensores do joelho (EJ), enquanto o impulso acima do TC (W’) é maior para EJ do que FP. Assim, esperamos que a tolerância ao exercício seja maior para EJ do que FP somente durante o exercício realizado acima de TC. Após a determinação da CVM, 11 homens realizaram dois testes All-Out de 5 min para determinar TC e W’. Os onze sujeitos realizaram mais 5 testes isométricos intermitentes até a falha da tarefa, durante 5 visitas, + 5% TC e - 5% TC para ambos os músculos, e 1 teste para EJ na mesma intensidade de exercício em (% CVM) correspondente a + 5% TC do FP. Os onze participantes realizaram mais 4 testes isométricos intermitentes, até a exaustão, + 5% e - 5% do TC e 1 teste para EJ na intensidade do exercício (% CVM) correspondente a + 5% do TC do FP, para o EJ. O W '(7243,2 ± 1942,9 vs. 3357,4 ± 1132,3 N · m · s) e CT (84,4 ± 24,8 vs. 73,9 ± 19,5 N · m) foram significativamente menores para FP em comparação com EJ. A tolerância ao exercício foi significativamente mais longa para FP (300,7 ± 156,7 s) do que EJ (156,7 ± 104,3 s) em CVM semelhante (~60%) e significativamente menor para FP (300,7 ± 156,7 s) do que EJ (697,0 ± 243,7 s) na condição de + 5% do TC. No entanto, nenhuma diferença significativa foi observada para condição de - 5% do TC (EJ = 1030,2 ± 495,4 s vs. FP = 1028,3 ± 514,4 s). Assim, o limite de tolerância durante as contrações isométricas submáximas é influenciado pela CVM absoluta apenas durante o exercício realizado em intensidade acima do TC, o que parece ser explicado por diferenças nos valores de TC (expressos em % CVM) e o W’. / The objective of this study was to test the hypotheses that critical torque (CT) (expressed as % maximal voluntary contraction; MVC) is higher for plantar flexors (PF) than knee extensors (KE) muscles, whereas impulse above ET (W’) is higher for KE than PF. Thus, we expected that exercise tolerance would be longer for KE than PF only during the exercise performed above ET. After the determination of MVC, 11 men performed two 5-min all-out tests to determine ET and IET. Eleven participants performed a further 4 intermittent isometric tests, to exhaustion, at ET + 5% and ET – 5%, and 1 test for KE at the exercise intensity (%MVC) corresponding to ET + 5% of PF. The W’ (7243.2 ± 1942.9 vs. 3357.4 ± 1132.3 N·m·s) and CT (84.4 ± 24.8 vs. 73.9 ± 19.5 N·m) were significantly lower in PF compared with KE. The exercise tolerance was significantly longer for PF (300.7 ± 156.7 s) than KE (156.7 ± 104.3 s) at similar %MVC (�����60%), and significantly shorter for PF (300.7 ± 156.7 s) than KE (697.0 ± 243.7 s) at ET + 5% condition. However, no significant difference was observed for ET – 5% condition (KE = 1030.2 ± 495.4 s vs. PF = 1028.3 ± 514.4 s). Thus, the limit of tolerance during submaximal isometric contractions is influenced by absolute MVC only during exercise performed above ET, which seems to be explained by differences on both CT (expressed as %MVC) and W’ values.

Submitted by FABIAN RODRIGO CASTRO FORERO null (fabiancastroforero@yahoo.com) on 2016-05-25T17:32:02Z No. of bitstreams: 1 castro_fr_me_ilha.pdf: 5058433 bytes, checksum: bf5b2af2ddbd3137fd6e825d60119c97 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-05-31T13:28:40Z (GMT) No. of bitstreams: 1 castro_fr_me_ilha.pdf: 5058433 bytes, checksum: bf5b2af2ddbd3137fd6e825d60119c97 (MD5) / Made available in DSpace on 2016-05-31T13:28:40Z (GMT). No. of bitstreams: 1 castro_fr_me_ilha.pdf: 5058433 bytes, checksum: bf5b2af2ddbd3137fd6e825d60119c97 (MD5) Previous issue date: 2016-03-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O pé é o órgão base da sustentação do corpo humano que está constantemente submetido a esforços para garantir a estabilidade deste. Analisando-se a distribuição de força na região plantar de indivíduos, pode-se inferir a respeito de patologias nos pés, problemas posturais e de equilíbrio. O estudo da distribuição de força na região plantar é feito com o baropodômetro, um equipamento composto por sistemas de hardware e software. Neste trabalho é apresentado o desenvolvimento de um baropodômetro implementado no Laboratório de Instrumentação e Engenharia Biomédica do Departamento de Engenharia Elétrica, UNESP – Campus Ilha Solteira, constituído por 120 sensores resistivos, tipo Force Sensing Resistor (FSR), dispostos matricialmente em duas plataformas, e por circuitos de aquisição de dados, comunicação e interfaceamento. Com as informações obtidas, por meio do software é possível identificar deformidades na região plantar e locais desta região submetidos a forças elevadas. Foram feitos testes em um grupo de 30 voluntários com diferentes faixas etárias e diferentes graus de escoliose. Inicialmente os voluntários foram divididos em dois grupos, sendo que o grupo G2 (45-78 anos) apresentou valores de estabiliometria maiores quando comparados com o G1 (13-30 anos). De forma similar, foi segmentada a mesma população (N=30) em dois grupos, segundo o grau de escoliose, GrA (0-9°) e GrB (10-32°). O grupo GrB mostrou maiores valores de estabiliometria do que o GrA e foi possível determinar que quanto maior o grau de escoliose menor a dependência das variáveis de estabiliometria com a idade. / The foot is the main support organ of the human body that is constantly subjected to efforts to ensure the stability of the body. Analyzing the distribution of force in the plantar region of individuals, it is possible to infer about feet pathologies, postural and balance problems, among others. The study of foot force distribution is made with the baropodometer, an equipment composed by hardware and software systems. This work describes the baropodometer developed at the Instrumentation and Biomedical Engineering Laboratory at the Department of Electrical Engineering, UNESP – Ilha Solteira, composed of 120 resistive sensors (Force Sensing Resistor - FSR) arranged in matrix on two platforms. Furthermore, acquisition and communication boards and software made in LabVIEW were developed. With the information obtained, with the software it is possible to identify deformities in the plantar region and sites of this region subjected to high forces. Tests in 30 volunteers with different ages and different scoliosis angles were made. Firstly, the volunteers were divided into two groups according to ages. The second group G2 (45-78 years old) had higher stabilometry values than first group G1 (13-30 years old). Secondly, the 30 volunteers were divided in two groups according scoliosis angles, GrA (0-9°) e GrB (10-32°). The GrB group showed higher stabilometry values than the GrA group, and it was possible to determine that the higher the degree of scoliosis the lower the dependency of stabiliometry variables with the age.

Orientador: Aparecido Augusto de Carvalho / Resumo: O pé é o órgão base da sustentação do corpo humano que está constantemente submetido a esforços para garantir a estabilidade deste. Analisando-se a distribuição de força na região plantar de indivíduos, pode-se inferir a respeito de patologias nos pés, problemas posturais e de equilíbrio. O estudo da distribuição de força na região plantar é feito com o baropodômetro, um equipamento composto por sistemas de hardware e software. Neste trabalho é apresentado o desenvolvimento de um baropodômetro implementado no Laboratório de Instrumentação e Engenharia Biomédica do Departamento de Engenharia Elétrica, UNESP – Campus Ilha Solteira, constituído por 120 sensores resistivos, tipo Force Sensing Resistor (FSR), dispostos matricialmente em duas plataformas, e por circuitos de aquisição de dados, comunicação e interfaceamento. Com as informações obtidas, por meio do software é possível identificar deformidades na região plantar e locais desta região submetidos a forças elevadas. Foram feitos testes em um grupo de 30 voluntários com diferentes faixas etárias e diferentes graus de escoliose. Inicialmente os voluntários foram divididos em dois grupos, sendo que o grupo G2 (45-78 anos) apresentou valores de estabiliometria maiores quando comparados com o G1 (13-30 anos). De forma similar, foi segmentada a mesma população (N=30) em dois grupos, segundo o grau de escoliose, GrA (0-9°) e GrB (10-32°). O grupo GrB mostrou maiores valores de estabiliometria do que o GrA e foi possível determi... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The foot is the main support organ of the human body that is constantly subjected to efforts to ensure the stability of the body. Analyzing the distribution of force in the plantar region of individuals, it is possible to infer about feet pathologies, postural and balance problems, among others. The study of foot force distribution is made with the baropodometer, an equipment composed by hardware and software systems. This work describes the baropodometer developed at the Instrumentation and Biomedical Engineering Laboratory at the Department of Electrical Engineering, UNESP – Ilha Solteira, composed of 120 resistive sensors (Force Sensing Resistor - FSR) arranged in matrix on two platforms. Furthermore, acquisition and communication boards and software made in LabVIEW were developed. With the information obtained, with the software it is possible to identify deformities in the plantar region and sites of this region subjected to high forces. Tests in 30 volunteers with different ages and different scoliosis angles were made. Firstly, the volunteers were divided into two groups according to ages. The second group G2 (45-78 years old) had higher stabilometry values than first group G1 (13-30 years old). Secondly, the 30 volunteers were divided in two groups according scoliosis angles, GrA (0-9°) e GrB (10-32°). The GrB group showed higher stabilometry values than the GrA group, and it was possible to determine that the higher the degree of scoliosis the lower the dependency of... (Complete abstract click electronic access below) / Mestre