Systems which exhibit nonreciprocal transmission or that can be used as logic functions are of great interest for the development of essential devices to nanotechnology. In this work, we investigate the transmission properties for two kinds of coupled discrete nonlinear chains configurations. In the first structure, it was explored the diode-like behavior, while in the other, it was showed the performance of different logic gates. The two systems were described by a set of the discrete nonlinear Schrödinger equations within a tight-binding approach. We determine their respective transmission spectrum. The first system is a nonlinear dimer coupled to linear side chains. We investigate the influence of the saturation of the nonlinear response on the nonreciprocal transmission, which had not been well studied in the previous literature. Through the analysis of the transmission spectrum, we unveil that, in regions of bistable behavior (windows), the difference between transport from right to left and transport from left to right is greater. Moreover these windows widen and displace to regions where the incident amplitude is larger as saturation is considered. The calculation of rectifying factor showed that, in the second bistability window, the influence of the saturation parameter has distinct actions over short- and long-wavelength. In the first window, the rectifying action is not compromised by the saturation. So weak saturation can improve the efficiency of the nonreciprocal transmission. The second system is a Y-shaped structure, on which three linear chains are joined by a nonlinear site. This kind of structure has been studied in the context of DNA-based devices. We investigated the capability of our model system to perform logic gate operations based on the transmission of phase-shifted incoming waves. Using a digitalization scheme of the output signal based on amplitude modulation, we show that AND, OR and XOR logic gate can be achieved. The phase-shifting between the incoming waves is required for the OR logic gate to be realizable and strong nonlinearity favors the existence of logic gates in the regime of short wavevectors. The analysis of the contrast ratio shows that optimal operation of the AND and OR logic gates takes place when the nonlinear response is the predominant physical property distinguishing the coupling and regular sites. We concluded that Y-shaped structures can potentially perform distinct logic functions. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Sistemas que apresentam transmissão não reciproca ou que possam ser usados em funções lógicas são de grande interesse para a construção de dispositivos essenciais ao desenvolvimento da nanotecnologia. Neste trabalho, investigamos as propriedades de transmissão em duas configurações de cadeias quase unidimensionais, discretas e não lineares. Em uma delas foi explorado o comportamento tipo diodo, e na outra, o surgimento de diferentes tipos de portas lógicas. Ambos os sistemas foram modelados através de um conjunto de equações de Schrödinger discretas não lineares dentro de aproximação tight binding e obtidos seus respectivos espectros de transmissão. O primeiro sistema consiste em um dímero não linear acoplado a duas cadeias lineares no qual investigamos a influência da saturação da resposta não linear na obtenção de transmissão não recíproca, até então ainda não estudada. Através da análise do espectro de transmissão, pudemos mostrar que nas regiões de comportamento biestável (chamados de janelas de biestabilidade), a diferença entre o transporte da direita para esquerda e o transporte da esquerda para direita é mais pronunciada a medida que se aumenta o coeficiente de saturação da não linearidade. Estas janelas se ampliam e são deslocadas para regiões onde a amplitude das ondas incidentes são maiores. O cálculo do fator de retificação nos permitiu mostrar ainda que a influência da saturação se dá de maneira diferente nas janelas de biestabilidade. Enquanto na segunda janela o comportamento é diferente em pequeno e grande comprimento de onda, na primeira isso não ocorre. Portanto, pudemos concluir que valores intermediários da saturação favorecem o transporte unidirecional. O segundo sistema consiste de uma estrutura tipo Y, na qual três cadeias lineares são unidas por um sítio não linear. Esse tipo de estrutura tem sido muito investigado em nanoestruturas de DNA. Investigamos a capacidade deste sistema realizar operações de portas lógicas baseadas na transmissão de ondas incidentes com diferença de fase. Usando um esquema de digitalização do sinal de saída baseado na modulação da amplitude, mostramos que portas AND, OR, e XOR podem ser encontradas. A diferença de fase entre as ondas incidentes é responsável pela existência das portas tipo OR enquanto que fortes não linearidades favorecem a realização de portas lógicas na região de pequeno vetor de onda. A análise do contraste, grandeza que mede a eficiência da porta lógica, mostrou que portas lógicas AND e OR são melhores quando os sítios regulares e o de acoplamento são distintos apenas pela resposta não linear. Concluímos que estruturas tipo Y têm grande potencial para realização de portas lógicas.

nÃo hà / Neste trabalho foi realizado um estudo numÃrico do interferÃmetro de Sagnac baseado em cristais fotÃnicos e de acoplador Ãptico de metamaterial. Na simulaÃÃo do interferÃmetro foram analisados os efeitos da propagaÃÃo da luz, considerando-se a dispersÃo de velocidade de grupo (GVD) e de terceira ordem (TOD), espalhamento Raman intrapulso, auto-inclinaÃÃo (Self-steepening) e auto-modulaÃÃo de fase na equaÃÃo nÃo linear de SchrÃdinger generalizada. No primeiro momento foi realizado o estudo para quatro fatores de razÃo de divisÃo da potÃncia incidente em uma das portas do dispositivo e trÃs dimensÃes para o comprimento do anel do dispositivo. Para caracterizar o desempenho do sistema, foram analisadas as curvas de transmissÃo, taxa de extinÃÃo, crosstalk e fator de compressÃo do pulso transmitido. No segundo momento, foi verificada a performance do chaveamento nÃo-linear para obtenÃÃo de porta lÃgica sob ModulaÃÃo por Amplitude de Pulsos (PAM). Excitando-se as duas portas de entrada do dispositivo com nÃveis lÃgicos "0" e "1", observando o seu comportamento em uma das saÃdas do dispositivo. Inicialmente, variou-se o parÃmetro de ajuste da modulaÃÃo (|ε|), obtendo-se apenas a porta lÃgica OR. E, em uma segunda aplicaÃÃo, manteve-se o parÃmetro da modulaÃÃo fixa e variou-se a fase de uma das portas de entrada, de 0 a 2π rad, encontrando-se portas lÃgicas do tipo OR, AND e XOR. TambÃm foram estudadas as caracterÃsticas de um guia metamaterial que possui a parte real da permissividade elÃtrica e da permeabilidade magnÃtica negativas. Esse guia metamaterial à acoplado com um guia convencional, observando-se as caracterÃsticas de transmissÃo e potÃncia crÃtica desse tipo de acoplador e, comparando-se com um acoplador convencional. Para essa anÃlise foi utilizado um perfil de automodulaÃÃo decrescente linearmente com cinco valores mÃnimo, observando-se um comportamento de histerese. / In this paper we present a numerical study of the Sagnac interferometer based on photonic crystals and optical coupler metamaterial. In the simulation of the interferometer effects of light propagation were analyzed, considering the dispersion of the group velocity (GVD) and third order (TOD), intrapulse Raman scattering, self-slope (self-steepening) and self-modulation phase in the generalized non-linear SchrÃdinger equation. The first time the study was conducted for four power division ratio of factors incident in one of the device ports and three dimensions for the device ring length. To characterize the system performance, were analyzed the transmission curves, extinction ratio, crosstalk and compression factor of the transmitted pulse. In the second moment, the performance of the non-linear switching was observed for obtaining gate under Pulse Amplitude Modulation (PAM). Exciting the two device input ports with logical levels "0" and "1", observing their behavior in one of the device outputs. Initially, the modulation is varied adjustment parameter (| ε |), obtaining only the logical OR gate. And in a second application, the fixed modulation parameter remained and was varied the phase of the input ports 0 to 2π rad, lying type logic gate OR, AND and XOR. The characteristics of a metamaterial guide that has the real part of electrical permittivity and magnetic permeability negatives were also studied. This metamaterial guide is coupled to a conventional guide, observing the transmission characteristics and critical power of this type of coupler and compared with a conventional coupler. For this analysis we used a decreasing automodulation profile linearly with five minimum, observing a hysteresis behavior.

Para poder satisfacer la demanda de mayores anchos de banda y los requisitos de los nuevos servicios, se espera que se produzca una evolución de las redes ópticas hacia arquitecturas reconfigurables dinámicamente. Esta evolución subraya la importancia de ofrecer soluciones en la que la escalabilidad y la flexibilidad sean las principales directrices. De acuerdo a estas características, las redes ópticas de conmutación de paquetes (OPS) proporcionan altas capacidades de transmisión, eficiencia en ancho de banda y excelente flexibilidad, además de permitir el procesado de los paquetes directamente en la capa óptica. En este escenario, la solución all-optical label switching (AOLS) resuelve el cuello de botella impuesto por los nodos que realizan el procesado en el dominio eléctrico. A pesar de los progresos en el campo del networking óptico, las redes totalmente ópticas todavía se consideran una solución lejana . Por tanto, es importante desarrollar un escenario de migración factible y gradual desde las actuales redes ópticas basadas en la conmutación de circuitos (OCS). Uno de los objetivos de esta tesis se centra en la propuesta de escenarios de migración basados en redes híbridas que combinan diferentes tecnologías de conmutación. Además, se analiza la arquitectura de una red OPS compuesta de nodos que incorporan nuevas funcionalidades relacionadas con labores de monitorización y esquemas de recuperación. Las redes ópticas permiten mejorar la transparencia de la red, pero a costa de aumentar la complejidad de las tareas de gesión. En este escenario, la monitorización óptica de prestaciones (OPM) surge como una tecnología capaz de facilitar la administración de las redes OPS, en las que cada paquete sigue su propia ruta en la red y sufre un diferente nivel de degradación al llegar a su destino. Aquí reside la importancia de OPM para garantizar los requisitos de calidad de cada paquete. / Vilar Mateo, R. (2010). Optical performance monitoring in optical packet-switched networks [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8926 / Palancia

Reconfigurable field effect transistors (RFET) have the ability to toggle polarity between n- and p- conductance at runtime [1], [2]. The here presented multiple independent gate (MIG) RFET expands the device functionality by offering additional logical inputs, valuable for e.g. efficient XOR or majority gate implementations [3], [4] or the here originally presented multiplexer circuit. Moreover,https://inspec.iet.org/ideas/#controlled-terms for the first time with a top-down RFET approach equal ON-currents are obtained for every configuration while requiring only one supply voltage (VDD).

Silicon Nanowire (SiNW) based reconfigurable fieldeffect transistors (RFETs) provide an additional gate terminal called the program gate which gives the freedom of programming p-type or n-type functionality for the same device at runtime. This enables the circuit designers to pack more functionality per computational unit. This saves processing costs as only one device type is required, and no doping and associated lithography steps are needed for this technology. In this paper, we present a complete design flow including both logic and physical synthesis for circuits based on SiNW RFETs. We propose layouts of logic gates, Liberty and LEF (Library Exchange Format) files to enable further research in the domain of these novel, functionally enhanced transistors. We show that in the first of its kind comparison, for these fully symmetrical reconfigurable transistors, the area after placement and routing for SiNW based circuits is 17% more than that of CMOS for MCNC benchmarks. Further, we discuss areas of improvement for obtaining better area results from the SiNW based RFETs from a fabrication and technology point of view. The future use of self-aligned techniques to structure two independent gates within a smaller pitch holds the promise of substantial area reduction.

In this paper, we consider devices, circuits, and systems comprised of transistors with integrated ferroelectrics. Said structures are actively being considered by various semiconductor manufacturers as they can address a large and unique design space. Transistors with integrated ferroelectrics could (i) enable a better switch (i.e., offer steeper subthreshold swings), (ii) are CMOS compatible, (iii) have multiple operating modes (i.e., I-V characteristics can also enable compact, 1-transistor, non-volatile storage elements, as well as analog synaptic behavior), and (iv) have been experimentally demonstrated (i.e., with respect to all of the aforementioned operating modes). These device-level characteristics offer unique opportunities at the circuit, architectural, and system-level, and are considered here from device, circuit/architecture, and foundry-level perspectives.

We report on a novel silicon nanowire-based field effect transistor with integrated ferroelectric gate oxide. The concept allows tuning the carrier transport in a non-volatile approach by switching the polarization in the ferroelectric layer close to the source Schottky-junction. We interpret the results in terms of tuning the transmissibility of the Schottky-junction for charge carriers. The experimental results provide a first step towards the integration of memory-in-logic concepts with reconfigurable nanowire transistors.

Logic-in-memory circuits promise to overcome the von-Neumann bottleneck, which constitutes one of the limiting factors to data throughput and power consumption of electronic devices. In the following we present four-input logic gates based on only two ferroelectric FETs (FeFETs) with hafnium oxide as the ferroelectric material. By utilizing two complementary inputs, a XOR and a XNOR gate are created. The use of only two FeFETs results in a compact and nonvolatile design. This realization, moreover, directly couples the memory and logic function of the FeFET. The feasibility of the proposed structures is revealed by electrical measurements of HKMG FeFET memory arrays manufactured in 28nm technology.

My thesis is devoted to the study of transport properties of Silicon Nanowires obtained by a bottom-up approach. The choice for the material system has been limited to undoped SiNWs because they are considered as the ultimate choice for ultrascaled electronic devices. For these systems, the problem of an effective carrier injection in the semiconductor is particularly important. The mechanism of carrier injection in Gate-All-Around Schottky barrier transistors was studied by temperature dependent measurements. Multiple gates are used to discriminate between different device switching mechanisms occurring either at the source and drain contacts, or at the level of the silicon channel. The gating scheme has proved be effective in suppressing the Schottky barrier enabling carrier injection at low temperature. Moreover, different electronic functionalities like p-n junctions and logic gates can be successfully implemented in such devices without the need of doping. I will describe a novel technique for the fabrication of metal silicide contacts to individual silicon nanowires based on an electrically-controlled Joule annealing process. This has enabled the realization of silicide-silicon-silicide tunnel junctions with silicon channel lengths down to 8nm. The silicidation of silicon nanowires by Nickel and Platinum could be observed in-situ and in real time by performing the experiments of Joule assisted silicidation in the chamber of a Scanning Electron Microscope. Lastly, signatures of resonant tunneling through an isolated Platinum Silicide cluster were detected in a Silicon tunnel junction. Tunneling spectroscopy in a magnetic field revealed the Zeeman splitting of the ground and the excited states.

MENEZES, José Wally Mendonça. Análise de performance de sólitons ópticos espaço-temporais em guia planar com não-linearidade cúbico quintica periodicamente modulada e circuitos lógicos operando nos regimes Kerr instantâneo e relaxado. 2010. 149 f. Tese (Doutorado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2010. / Submitted by francisco lima (admir@ufc.br) on 2014-06-30T18:38:52Z No. of bitstreams: 1 2010_tese_jwmmenezes.pdf: 7446687 bytes, checksum: 708020e7c4ad24658a46a55f2af5ebc6 (MD5) / Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2014-08-06T20:53:00Z (GMT) No. of bitstreams: 1 2010_tese_jwmmenezes.pdf: 7446687 bytes, checksum: 708020e7c4ad24658a46a55f2af5ebc6 (MD5) / Made available in DSpace on 2014-08-06T20:53:00Z (GMT). No. of bitstreams: 1 2010_tese_jwmmenezes.pdf: 7446687 bytes, checksum: 708020e7c4ad24658a46a55f2af5ebc6 (MD5) Previous issue date: 2010 / In this work, the propagation and stability of spatiotemporal optical solitons (or optical bullets) in a planar waveguide with periodically modulated cubic-quintic nonlinearity is presented numerically as a function of the amplitudes of modulation , the frequency of modulation and the propagation distance .With the objective of ensure the stability and preventing the collapse or the spreading of pulses, in this study we explore the cubic-quintic nonlinearity with the optical fields coupled by XPM (Cross-Phase Modulation) and take into account several values for the nonlinear parameter , for amplitudes and frequency of modulation as a function of the propagation distance , we cause the collisions of two pulses (envelope of the optical field) to ensure that the optical pulse are sólitons and, after numerical analysis was possible shown the existence of stable spatiotemporal optical sóliton. We also have presented the numerical analysis of the three-core nonlinear fiber coupler in a symmetrical planar structure and operating with instantaneous and relaxed Kerr model for generation of the all-optical logic gates. To implement this optical circuit, we used a control pulse CP with a phase difference between the inputs “I1” and “I2” of the fiber coupler and were analyzed the transmission characteristics, the Extinction Ratio as a function of the phase difference, the length normalized (LN), the figure-of-merit of the logic gates (FOMELG (dB) and the pulse evolution along the fiber coupler and, thus, ensure were demonstrated the possibilities for generating of the all-optical logic gates. / Neste trabalho, a propagação e estabilidade de sólitons espaço-temporais (ou sólitons balas) em um guia de onda planar com não linearidade cúbico quintica periodicamente modulada é apresentada em função da amplitude de modulação , da freqüência de modulação e da distância de propagação . Com o objetivo de garantir a estabilidade e prevenir o colapso ou o espalhamento dos pulsos, exploramos a não-linearidade cúbico quintica com os campos ópticos acoplados por XPM (Modulação de Fase Cruzada) e utilizando diversos valores para o parâmetro não-linear , para as amplitudes e freqüências de modulação em função da distância de propagação , provocamos a colisão de dois pulsos (campos ópticos) para garantir que estes sejam realmente sólitons e, após estas análises numéricas, foi possível mostrar a existência de sólitons espaço-temporais estáveis. Apresentamos, também, a análise numérica de um acoplador triplo não linear de fibras ópticas em uma estrutura planar simétrica e operando com o modelo Kerr instantâneo e relaxado para geração de portas lógicas ópticas. Para implementar estes circuitos, usamos um pulso de controle CP com uma diferença de fase entre as entradas “I1” e “I2” do acoplador e analisamos as características de transmissão, taxa de extinção em função da diferença de fase, a largura normalizada (LN), a figura de mérito para portas lógicas FOMELG(dB) e a evolução dos pulsos ao longo do acoplador e, assim, foi demonstrado as possibilidades para geração das portas lógicas ópticas.