This dissertation describes experimental studies of the superconducting proximity effect in single-crystal Pb, Sn, and Zn nanowires of lengths up to 60 um, with both ends of the nanowires in contact with macroscopic electrodes that are either superconducting (Sn or Pb) or non-superconducting (Au). The Pb, Sn, and Zn nanowires are fabricated using a template-based electrochemical deposition method. Electric contacts to the nanowires are formed in situ during electrochemical growth. This method produces high transparency contacts between a pair of macroscopic electrodes and a single nanowire, circumventing the formation of oxide or other poorly conducting interface layers. Extensive analyses of the structure and the composition of the nanowire samples are presented to demonstrate that (1) the nanowires are single crystalline and (2) the nanowires are clean without any observable mixing of the materials from the electrodes. The nanowires being investigated are significantly longer than the nanowires with which electrode-induced superconductivity was previously investigated by other groups. We have observed that in relatively short (~6 um) Sn and Zn nanowires, robust superconductivity is induced at the superconducting transition temperatures of the electrodes. When Sn and Pb nanowires are in contact with a pair of Au electrodes, superconductivity is suppressed completely. For nanowires of 60 um in length, although the suppression of superconductivity by Au electrodes is only partial, the induced superconductivity at the higher transition temperatures of the electrodes remains full and robust. Therefore, an anomalous superconducting proximity effect has been observed on a length scale which far exceeds the expected length based on the existing theories of the proximity effect. The measured current-voltage characteristic of the nanowires reveals more details such as hysteresis, multiple Andreev reflection, and phase-slip centers. An interesting relation between the proximity effect and the residual-resistance-ratio of the nanowires has also been observed. Possible mechanisms for this proximity effect are discussed based on these experimental observations.

This study presents a new process to fabricate gapless triangular micro-lens array (GTMA). The process includes optical simulation with tracepro, UV lithography, photoresist reflow process, Ni electroplating and hot embossing technique. After photoresist triangular column array is defined using UV lithography, reflow process is applied to melt photoresist triangular column array into the shape of triangular micro-lens array. With this reflowed triangular micro-lens array, Ni is deposited and covered uniformly on the triangular micro-lens array using electroplating. The growth rate of Ni is controlled at electroplating current density of 1 Ampere Square Decimeter (ASD; A/dm2). After this electroplating process is finished, a mold of GTMA is obtained, which is served as primary mold. Subsequently, with passivation technique applied on this mold¡¦s surface, electroplating process is applied again to obtain a secondary mold. Next, this secondary mold is served as master for the subsequent hot embossing process to replicate the GTMA pattern onto polymeric material PMMA and PET sheet. The mold with stiffness and hardness plays an important role in GTMA hot embossing process. In addition, this GTMA used as optical film can offer a 100 % fill factor and a simulation of optical coupling efficiency of 66.7% to improve luminance of backlight module (BLM). In addition, this study presents the fabricated molds of GTMA with different aspect-ratio about 0.109 and 0.133. The optical measurement of BLM shows that this optical film of GTMA pattern with aspect-ratio about 0.109 can increase 15.1% of luminance and with aspect-ratio about 0.133 can increase 22.1% of luminance.

ABSTRACT The polishing stocks used in various ultra-precision polishing machines consist of abrasives, polishing disk (pad), and polishing fluids. They are expendable goods. To ensure the machining ability and the repeat accuracy of machining characteristics, the polishing disc (pad) must use the dressing mechanism to produce sharp new grains. As a result, the grinding surface on the abrasive wheel becomes thinner gradually, then losses it¡¦s machining ability, and finally must be changed. Hence, in this project, an idea of an ultra-precision abrasive machining is proposed by using the continuous composite electroplating on the polishing disc. In this idea, the machining ability of Cu polishing disc can be ensured due to the use of the continuous Sn-Al2O3 composite electroplating. Hence, it can save the cost of the ultra-precision machining using in the semiconductor wafer. In this study, after 60 minutes continuous composite electroplated polishing, the thickness of the composite coating on the surface of Cu polishing disc can increase 6.13£gm. It means the surface of disc can be grew and renewed at every moment. The removal amount of the wafer is 10.8£gm. The surface of wafer was Ra=0.5453£gm and Rmax=5.464£gm at the start ,but came to Ra=0.0019£gm and Planess=2.649£gm/36mm after 60 minutes polishing.

Thesis (doctoral)--University of Helsinki, 2000. / Includes bibliographical references. Also available on the World Wide Web.

No description available.

A MEMS based electrostatic field sensor is presented which uses capacitive interrogation of an electrostatic force deflected microstructure. First the deflection of the sensor’s membrane which is caused by electrostatic force in the presence of electric field is calculated both by simulation and theoretical model and it has been shown that the results of the simulations have acceptable values compared to the theoretical ones. Simulation models have also been designed to improve the vibration of the membrane for measuring the ac electric fields. It has been shown that by adding perforations to the surface of the membrane, it is possible to reduce the air drag force effect on the membrane and still have similar electrostatic force on the membrane. Therefore, it is possible to reduce the damping due to air resistance in membrane movement when measuring ac fields. After successful modeling of the sensor structure, the fabrication process for the sensor has been designed. The electroplating process as the most important fabrication step has been studied in detail prior to starting the fabrication of sensor. The process parameters for electroplating process, such as current amplitudes, duty cycle and frequency have been optimized to get the lowest surface roughness to thickness ratio for the electroplated films. A lithography molding process was developed for the electroplating. Both dc and pulse plated films have been studied to show the role of pulse plating in improving the quality of the electroplated films. It was found during the release process that the electroplated copper interacted with sulfur during plasma etching of silicon. However, the result of the releasing process was very helpful to find the best recipe of releasing and they can be used in next projects.

Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [119]-126).

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 77-98).

Made available in DSpace on 2014-06-11T19:34:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2004Bitstream added on 2014-06-13T19:47:49Z : No. of bitstreams: 1 padilha_rq_dr_guara.pdf: 4651598 bytes, checksum: 77a7edcf3c2fe16e30e62ec60549c1f8 (MD5) / Universidade Estadual Paulista (UNESP) / Este estudo objetiva analisar a influência da espessura de uma camada intermediária de níquel químico sob cromo duro eletrodepositado no aço de alta resistência, ABNT 4340 (utilizado em trens de pouso de aeronaves), com dureza de 39 HRc e 52 HRc. A análise é realizada por meio de dados obtidos nos ensaios de fadiga por flexão rotativa, das amostras revestidas com cromo duro, com e sem camada intermediária de níquel químico. As espessuras com melhor desempenho foram submetidas a ensaio de fadiga axial, em corpos de prova com e sem entalhe. Os resultados demonstram que a aplicação da camada de níquel químico é benéfica, em todas as espessuras analisadas, porém, há espessura que seu desempenho é ainda melhor. O tema proposto surgiu do interesse da ELEB - Embraer Liebherr Equipamentos do Brasil, em buscar por novas alternativas ou melhorias ao atual revestimento de cromo duro convencional. / The aim of this study is to analyze the effect of the thickness of an intermediate layer of chemical nickel under chromium electroplating on a high resistance steel ABNT 4340 (used in aircrafts landing gears), with hardness of 39 and 52 HRc. The analysis is done through data obtained from rotating bending fatigue tests of samples coated with hard chromium, with and without intermediate layer of chemical nickel. The thickness with better performance are submitted to axial fatigue tests, with and without notch. The results demonstrate that the application of a layer of chemical nickel is beneficial, in all of the analyzed thickness although some thicknesses present even better performance. The proposed work is due to the interest of the Brazilian Company of Aeronautics, Division of Equipments - EMBRAER/ELEB - in searching for new alternatives or improvements to the current coating with conventional hard chromium.

abstract: To date, the most popular and dominant material for commercial solar cells is crystalline silicon (or wafer-Si). It has the highest cell efficiency and cell lifetime out of all commercial solar cells. Although the potential of crystalline-Si solar cells in supplying energy demands is enormous, their future growth will likely be constrained by two major bottlenecks. The first is the high electricity input to produce crystalline-Si solar cells and modules, and the second is the limited supply of silver (Ag) reserves. These bottlenecks prevent crystalline-Si solar cells from reaching terawatt-scale deployment, which means the electricity produced by crystalline-Si solar cells would never fulfill a noticeable portion of our energy demands in the future. In order to solve the issue of Ag limitation for the front metal grid, aluminum (Al) electroplating has been developed as an alternative metallization technique in the fabrication of crystalline-Si solar cells. The plating is carried out in a near-room-temperature ionic liquid by means of galvanostatic electrolysis. It has been found that dense, adherent Al deposits with resistivity in the high 10^–6 ohm-cm range can be reproducibly obtained directly on Si substrates and nickel seed layers. An all-Al Si solar cell, with an electroplated Al front electrode and a screen-printed Al back electrode, has been successfully demonstrated based on commercial p-type monocrystalline-Si solar cells, and its efficiency is approaching 15%. Further optimization of the cell fabrication process, in particular a suitable patterning technique for the front silicon nitride layer, is expected to increase the efficiency of the cell to ~18%. This shows the potential of Al electroplating in cell metallization is promising and replacing Ag with Al as the front finger electrode is feasible. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2016