Orientador: Lauro Tatsuo Kubota / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-08T22:44:52Z (GMT). No. of bitstreams: 1 Kisner_Alexandre_M.pdf: 3973690 bytes, checksum: 2810b47ecfaaac028a1bf271a3fc25a0 (MD5) Previous issue date: 2007 / Conjuntos de transistores de efeito de campo sensíveis a íons (ISFETs) foram desenvolvidos no presente trabalho. Implementou-se durante a fabricação destes uma etapa adicional de anodização que possibilitou a formação de uma fina camada de alumina porosa sobre suas portas. Esta serviu como dielétrico e também molde para o crescimento de nanocristais de Ag e Au sobre os dispositivos. Os transistores desenvolvidos foram divididos em dois conjuntos, onde as dimensões de porta de cada conjunto foram de 10 x 50 mm e 50 x 50 mm. Utilizando-se um processo simples de anodização, obteve-se sobre a porta dos transistores uma fina camada de alumina de aproximadamente 60 nm de espessura, contendo uma alta densidade de poros (~ 10 poros/cm) com diâmetro médio de 30 + 6 nm e distribuídos de forma regular. A implementação desta possibilitou não só um aumento significativo na área de porta, bem como molde para o crescimento de nanoestruturas de Ag e Au sobre os transistores, atuando assim como nanoeletrodos de porta. Os testes destes como sensores para soluções com diferentes valores de pH, mostraram que os dispositivos apresentam um curto tempo de resposta (t < 30 s) e que as nanoestruturas metálicas são capazes de aumentar a sensibilidade dos dispositivos em relação àqueles formados apenas por alumina. Os primeiros testes para a detecção de moléculas como glutationa, demonstraram que os ISFETs fabricados são capazes de detectar esta, mesmo sendo uma espécie com baixa densidade de carga, em concentrações submicromolares / Arrays of ion-sensitive field effect transistors (ISFETs) were developed in this work. An additional step in the fabrication process was employed to implement a thin film of porous anodic alumina on the gate. This porous layer works as dielectric and template to the vertical growth of Ag and Au nanocrystals on the gate. The produced ISFETs were divided in two groups, which the gate dimensions were 10 x 50 mm and 50 x 50 mm. Using a simple anodizing process, a 60 nm thickness porous anodic alumina was developed on the gate. This porous film presented a high density porosity (~ 10 pores/cm) with an average pore diameter of 30 + 6 nm and a regular distribution on the gate of those ISFETs. This porous film lead to a significant increase in the gate area and also worked as a template to the growth of Ag and Au nanocrystals, which were used as gate nanoelectrodes. The results of such sensors to detect different pH of the solutions showed that the produced ISFETs present a short response time (t < 30 s). Moreover, the presence of such Ag and Au nanostructures increased the sensors sensitivity in comparison to those observed without nanoelectrodes. The first results to detect species such as glutathione, indicated that the ISFETs are even sensitive to detect small charged species in a submicromolar concentration range / Mestrado / Quimica Analitica / Mestre em Química

In this dissertation work, the study focuses on large areal growth of MoS2 monolayers and a study of the structural, optical and electrical properties of such monolayers before and after transfer using a polymer-lift off technique. This work will discuss the issue of contact resistance and the effect of defects (both intrinsic and extrinsic) on the overall quality of the monolayer films. The significance of this dissertation work is that a reproducible strategy for monolayer MoS2 film growth and quantification of areal coverage as well as the detrimental effects of processing on device performance is presented.

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Graphene, a monolayer of carbon atoms, has gained prominence to augment existing chip-scale photonic and optoelectronic applications, especially for sensing in optical radiation, owing to its distinctive electrical properties and bandgap as well as its atomically thin profile. As a building block of photodetection, graphene has been co-integrated with mature silicon technology to realize the on-chip, high-performance photo-detecting platforms with broad spectral response from the deep-ultraviolet (UV) to the mid-infrared (MIR) regime. The recent state-of-the-art graphene-based photodetectors utilizing the combination of colloidal quantum dots (QDs) and graphene have been intensively studied, where QDs function as the absorber and the role of graphene is as a fast carrier recirculating channel. With such a configuration, an ultrahigh sensitivity can be achieved on account of the photogating mechanism; however, the response time is slow and limited to the millisecond-to-second range. To achieve balance between high sensitivity and fast response time, we have demonstrated a new photodetector that is based on graphene/two-dimensional heterostructures. The homogeneous thickness and the large contact of the heterostructure give rise to fast carrier transporting between the thin absorber layer and the graphene, leading to a fast response time. This thesis carefully investigates the optimization of fabrication as well as optoelectronic characterization of photodetectors based on graphene/semiconductor heterostructures field-effect transistors (GFETs). GFETs with different architectures were demonstrated and systematically studied under optical illumination ranging from deep-UV to MIR at varying optical powers. Noise behaviors have been studied under different device parameters such as device structure, area and gate-bias. Results show that the flicker noise of graphene-based devices can be explained by the McWhorter model in which the fluctuation of carrier numbers is the dominant process of noise in low frequencies; thus, it can be scaled down by reducing the number of introduced charged carriers with optimized fabrication. Besides, the impact of absorber on top of graphene and the bottom substrate has been comprehensively explored through various experimental techniques including current-voltage (IV), photo-response dynamics, and noise characterization measurements. With our configuration, the high sensitivity and fast response time of photodetectors can be obtained at the same time. In addition to this, the study of the bottom substrate with different doping levels suggests a concept of dual-photogating effect which is induced by the top absorbent material and the photoionization of the doped silicon substrate. In summary, this thesis showcases novel device architecture and fabrication procedures of GFETs photodetectors, optimizes device structure, quantifies the performance and evaluates the effect of various absorbent materials and substrate. It provides insight into the improvement of possible routes to achieve a broadband photo-detecting system with higher sensitivity, faster response time and lower noise level. / Doctor of Philosophy / The rapid expansion of networked devices and the development of the Internet of Things have given rise to an internet traffic and data explosion. Since conventional electrical interconnects are unable to rise to the occasion of the ever-growing demands of information technology and communication networking, next-generation alternative interconnects with higher performance and lower loss are attractive alternatives as the chip-scale optical interconnection. Among various optical interconnects, photodetectors play significant roles by converting optical input into electrical signal output. Sensing of light has a great impact in daily applications such as telecommunications, night vision, biomedical imaging and biochemical sensing. Graphene, belonging to the class of 2-dimensional materials, shows enormous potential as a building block of photodetection owing to its outstanding optical and electrical properties. One possible route to develop a sensitive and fast-operating on-chip photodetector is to integrate graphene into silicon photonics platforms since the latter has been widely studied and driven to maturity. In this thesis, graphene-based photodetectors with novel architectures have been fabricated, demonstrated and systematically investigated. Various measurements have been taken to quantify the performance of photodetectors in a wide detecting range from deep ultraviolet to mid-infrared.

The limitations of the conventional Cu/low-k interconnect technology for use in future ultra-scaled integrated circuits down to 7 nm in the year 2020 are investigated from the power/performance point of view. Compact models are used to demonstrate the impacts of various interconnect process parameters, for instance, the interconnect barrier/liner bilayer thickness and aspect ratio, on the design and optimization of a multilevel interconnect network. A framework to perform a sensitivity analysis for the circuit behavior to interconnect process parameters is created for future FinFET CMOS technology nodes. Multiple predictive cell libraries down to the 7‒nm technology node are constructed to enable early investigation of the electronic chip performance using commercial electronic design automation (EDA) tools with real chip information. Findings indicated new opportunities that arise for emerging novel interconnect technologies from the materials and process perspectives. These opportunities are evaluated based on potential benefits that are quantified with rigorous circuit-level simulations and requirements for key parameters are underlined. The impacts of various emerging interconnect technologies on the performances of emerging devices are analyzed to quantify the realistic circuit- and system-level benefits that these new switches can offer.

Since the first isolation of graphene in 2004 interest in superconductivity and the superconducting proximity effect in monolayer or few-layer crystals has grown rapidly. This thesis describes studies of both the proximity effect in single and fewlayer graphene flakes, as well as the superconducting transition in few unit cell chalcogenide flakes. Optical and atomic force microscopy and Raman spectroscopy have been used to characterise the quality and number of molecular layers present in these flakes. Graphene structures with superconducting Al electrodes have been realised by micromechanical cleavage techniques on Si/SiO2 substrates. Devices show good normal state transport characteristics, efficient back-gating of the longitudinal resistivity, and low contact resistances. Several trials have been made to investigate proximity-induced critical currents in devices with junction lengths in the range 250-750 nm. Unfortunately, no sign of proximity supercurrents was observed in any of these devices. Nevertheless the same devices have been used to carefully characterise proximity doping, (due to the deposited electrode), and weak localisation/anti-localisation contributions to the conductivity in them. In addition this work has been extended to investigations of the superconducting transition in few unit-cell dichalcogenide flakes. Four-terminal devices have been realised by micromechanical cleavage from a 2H-NbSe2 single crystal onto Si/SiO2 substrates followed by the deposition of Cr/Au contacts. While very thin NbSe2 flakes do not appear to conduct, slightly thicker flakes are superconducting with an onset ܶ௖ that is only slightly depressed from the bulk value (7.2K). The resistance typically shows a small, sharp, high temperature transition followed by one or more broader transitions, which end in a wide tail to zero resistance at low temperatures. These multiple transitions appear to be related to disorder in the layer stacking rather than lateral inhomogeneity. The behaviour of several flakes has been characterised as a function of temperature, applied field and back-gate voltage. The resistance and transition temperatures are found to depend weakly on the gate voltage. Results have been analysed in terms of available theories for these phenomena.

Darbo tikslas – išanalizuoti audinių šėrimą bei jo ypatumus, panaudojant racionus su skirtingu baltymų kiekiu ir skirtingu maisto medžiagų santykiu juose, stebėti laktuojančių audinių pieno produkcijos lygį, audinukų augimo spartą bei išsivystymą. Bandymo uždaviniai buvo: 1. Atrinkti analoginius gyvūnus ir juos suskirstyti į analogines grupes; 2. Sekti audinių pašarų ėdamumą ir laikymo sąlygas; 3. Sekti audinių pieno produktyvumą pagal atskiras grupes, nes kiekvienos grupės audinės buvo šeriamos skirtingais racionais pagal maisto medžiagų santykį; 4. Stebėti audinukų kūno masės priaugimą, kada jie buvo maitinami tik motinos pienu ir auginimo pabaigoje, t.y. įvertinti augimo ir vystimosi spartą. Tyrimus atlikome Lietuvos žvėrininkystės individualioje fermoje su audinėmis Mustela vison. Visos audinės buvo suskirstytos į 3 grupes: I gr. - racionas su dideliu baltymų kiekiu, II gr. - racionas su vidutiniu baltymų kiekiu, II gr. - racionas su mažu baltymų kiekiu. Šeriant audines skirtingais racionais, kur skyrėsi maisto medžiagų santykis: baltymai-riebalai-angliavandeniai nuo energijos kiekio, pirmoje grupėje buvo 63:35:2; antroje grupėje 45:41:14 ir trečioje grupėje 29:44:27, galime padaryti sekančias išvadas: 1. nustačius naudojamų pašarų maistinę ir energetinę vertes, baltymų didžiausias kiekis buvo pirmos grupės audinių racione ir sudarė 66,1 proc., nes jų racione buvo daugiau kaip 60 proc. žuvies ir žuvų produktų. Kitų grupių audinių racionuose riebalai ir angliavandeniai... [toliau žr. visą tekstą] / The aim of this work is to analyze the foddering of minks and its peculiarity, using rations with different amount of albumen and different proportion of nutritious matter in it; to watch the level of milk production during the period of mink lactation; to watch the speed of baby mink growing up and development. The tasks of the experiment: 1. To choose analogical animals and divide them into analogical groups; 2. To watch the fitness of mink fodder and their keeping conditions; 3. To watch the mink milk productivity in different groups because minks in every group were foddered on different rations according to the proportion of nutritious matter; 4. To watch baby mink gaining weight when they are fed on mother’s milk and at the end of mink breeding. The aim of it is to estimate the speed of growing up and development. The experiment was done in the individual farm of fur farming in Lithuania with Mustela Vison minks. All minks were divided into three groups: 1st group – ration with big amount of albumen; 2nd group – ration with average amount of albumen and 3rd group – ration with little amount of albumen. Foddering minks on various rations, where the proportion of nutritious matter was different: albumen – fat – carbohydrate from the amount of energy, in the 1st group it was 63:35:2; in the 2nd group 45:41:14 and in the 3rd group it was 29:44:27. After the experiment the following conclusions can be made: 1) When the nutritional and energetic value was settled, the biggest... [to full text]

Parameter variations introduced by manufacturing imprecision are becoming more influential on circuit performance. This is especially the case in emerging nanoscale fabrics due to unconventional manufacturing steps (e.g., nano-imprint) and aggressive scaling. These parameter variations can lead to performance deterioration and consequently yield loss. Parameter variations are typically addressed pre-fabrication with circuit design targeting worst-case timing scenarios. However, this approach is pessimistic and much of performance benefits can be lost. By contrast, if parameter variations can be estimated post-manufacturing, adaptive techniques or reconfiguration could be used to provide more optimal level of tolerance. To estimate parameter variations during run-time, on-chip variation sensors are gaining in importance because of their easy implementation. In this thesis, we propose novel on-chip variation sensors to estimate variations in physical parameters for emerging nanoscale fabrics. Based on the characteristics of systematic and random variations, two separate sensors are designed to estimate the extent of systematic variations and the statistical distribution of random variations from measured fall and rise times in the sensors respectively. The proposed sensor designs are evaluated through HSPICE Monte Carlo simulations with known variation cases injected. Simulation results show that the estimation error of the systematic-variation sensor is less than 1.2% for all simulated cases; and for the random-variation sensor, the worst-case estimation error is 12.7% and the average estimation error is 8% for all simulations. In addition, to address the placement of on-chip sensors, we calculate sensor area and the effective range of systematic-variation sensor. Then using a processor designed in nanoscale fabrics as a target, an example for sensor placement is introduced. Based on the sensor placement, external noises that may affect the measured fall and rise times of outputs are identified. Through careful analysis, we find that these noises do not deteriorate the accuracy of the systematic-variation sensor, but affect the accuracy of the random-variation sensor. We believe that the proposed on-chip variation sensors in conjunction with post-fabrication compensation techniques would be able to improve system-level performance in nanoscale fabrics, which may be an efficient alternative to making worst-case assumptions on parameter variations in nanoscale designs.

Scope and contents: The static and dynamic electrical characteristics of silicon n-channel MOS FETs are studied down to cryogenic temperatures. Particular emphasis is directed towards the effect of interface states on the temperature dependence of both the pinch-off voltage and 1/f noise. / No abstract included. / Thesis / Master of Engineering (MEngr)

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