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Hildreth, Owen James. "Development of metal-assisted chemical etching as a 3D nanofabrication platform." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/49011.
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The considerable interest in nanomaterials and nanotechnology over the last decade is attributed to Industry's desire for lower cost, more sophisticated devices and the opportunity that nanotechnology presents for scientists to explore the fundamental properties of nature at near atomic levels. In pursuit of these goals, researchers around the world have worked to both perfect existing technologies and also develop new nano-fabrication methods; however, no technique exists that is capable of producing complex, 2D and 3D nano-sized features of arbitrary shape, with smooth walls, and at low cost. This in part is due to two important limitations of current nanofabrication methods. First, 3D geometry is difficult if not impossible to fabricate, often requiring multiple lithography steps that are both expensive and do not scale well to industrial level fabrication requirements. Second, as feature sizes shrink into the nano-domain, it becomes increasingly difficult to accurately maintain those features over large depths and heights. The ability to produce these structures affordably and with high precision is critically important to a number of existing and emerging technologies such as metamaterials, nano-fluidics, nano-imprint lithography, and more. Summary To overcome these limitations, this study developed a novel and efficient method to etch complex 2D and 3D geometry in silicon with controllable sub-micron to nano-sized features with aspect ratios in excess of 500:1. This study utilized Metal-assisted Chemical Etching (MaCE) of silicon in conjunction with shape-controlled catalysts to fabricate structures such as 3D cycloids, spirals, sloping channels, and out-of-plane rotational structures. This study focused on taking MaCE from a method to fabricate small pores and silicon nanowires using metal catalyst nanoparticles and discontinuous thin films, to a powerful etching technology that utilizes shaped catalysts to fabricate complex, 3D geometry using a single lithography/etch cycle. The effect of catalyst geometry, etchant composition, and external pinning structures was examined to establish how etching path can be controlled through catalyst shape. The ability to control the rotation angle for out-of-plane rotational structures was established to show a linear dependence on catalyst arm length and an inverse relationship with arm width. A plastic deformation model of these structures established a minimum pressure gradient across the catalyst of 0.4 - 0.6 MPa. To establish the cause of catalyst motion in MaCE, the pressure gradient data was combined with force-displacement curves and results from specialized EBL patterns to show that DVLO encompassed forces are the most likely cause of catalyst motion. Lastly, MaCE fabricated templates were combined with electroless deposition of Pd to demonstrate the bottom-up filling of MaCE with sub-20 nm feature resolution. These structures were also used to establish the relationship between rotation angle of spiraling star-shaped catalysts and their center core diameter. Summary In summary, a new method to fabricate 3D nanostructures by top-down etching and bottom-up filling was established along with control over etching path, rotation angle, and etch depth. Out-of-plane rotational catalysts were designed and a new model for catalyst motion proposed. This research is expected to further the advancement of MaCE as platform for 3D nanofabrication with potential applications in thru-silicon-vias, photonics, nano-imprint lithography, and more.
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Anokhina, Ksenia. "Investigation of Metal-assisted Si Etching for Fabrication of Nanoimprint Lithography Stamps." Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-14459.
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This diploma thesis deals with the investigation of the metal-assisted catalytic etching (MaCE) of Si. One of the main goals is to study fabrication of stamps for nanoimprint lithography using MaCE. Formation of nanoporous silicon (PSi), Si nanowires (SiNWs) and three-dimensional nanostructures in Si by MaCE is demonstrated. For this purpose optical lithography, electron beam lithography (EBL), shadow mask evaporation and aerosol nanoparticles deposition techniques have been utilized. The etching rate and surface morphology of Si (with Au lift-off films as a catalyst) as functions of time and concentrations of chemicals are measured in the current diploma work using optical microscope and scanning electron microscopy (SEM). In the current thesis it is shown that Si structures with sub-150 nm lateral sizes, high aspect ratio (up to 1:21), well-defined shapes, and various complexity can easily be fabricated by means of MaCE process.
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Ngqoloda, Siphelo. "Vertically aligned silicon nanowires synthesised by metal assisted chemical etching for photovoltaic applications." University of the Western Cape, 2015. http://hdl.handle.net/11394/4872.
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>Magister Scientiae - MScOne-dimensional silicon nanowires (SiNWs) are promising building blocks for solar cells as they provide a controlled, vectorial transport route for photo-generated charge carriers in the device as well as providing anti-reflection for incoming light. Two major approaches are followed to synthesise SiNWs, namely the bottom-up approach during vapour-liquid-solid mechanism which employs chemical vapour deposition techniques. The other method is the top-down approach via metal assisted chemical etching (MaCE). MaCE provides a simple, inexpensive and repeatable process that yields radially and vertically aligned SiNWs in which the structure is easily controlled by changing the etching time or chemical concentrations. During MaCE synthesis, a crystalline silicon (c-Si) substrate covered with metal nanoparticles (catalyst) is etched in a diluted hydrofluoric acid solution containing oxidising agents. Since the first report on SiNWs synthesised via MaCE, various publications have described the growth during the MaCE process. However lingering questions around the role of the catalyst during formation, dispersion and the eventual diameter of the nanowires remain. In addition, very little information pertaining to the changes in crystallinity and atomic bonding properties of the nanowires post synthesis is known. As such, this study investigates the evolution of vertical SiNWs from deposited silver nanoparticles by means of in-depth electron microscopy analyses. Changes in crystallinity during synthesis of the nanowires are probed using x-ray diffraction (XRD) and transmission electron microscopy (TEM). Deviations in the optical properties are quantified using optical reflectivity measurements by employing ultraviolet-visible (UV-Vis) spectroscopy, whereas the bonding configurations of the nanowires are probed by Raman and Fourier transforms infrared spectroscopy. Diameters of 50 – 200 nm vertical SiNWs were obtained from scanning electron micrographs and nanowires lengths linearly increased with etching time duration from about 130 nm after 30 seconds to over 15 μm after 80 minutes. No diameter modulations along nanowires axial direction and rough nanowires apexes were observed for nanowires obtained at longer etching times. These SiNWs remained crystalline as their bulk single crystalline Si wafers but had a thin amorphous layer on the surface, findings confirmed by TEM, XRD and Raman analysis. Nanowires were found to be partially passivated with oxygen with small traces of hydrogen termination, confirmed with infrared absorption studies. Finally, low optical reflection of less than 10% over visible range compared to an average of 30% for bulk Si were measured depicting an antireflective ability required in silicon solar cells.
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Khanyile, Sfiso Zwelisha. "Silicon nanowires by metal-assisted chemical etching and its incorporation into hybrid solar cells." University of Western Cape, 2021. http://hdl.handle.net/11394/8340.
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Philosophiae Doctor - PhDThe rapid increase in global energy demand in recent decades coupled with the adverse environmental impact of conventional fuels has led to a high demand for alternative energy sources that are sustainable and efficient. Renewable solar energy technologies have received huge attention in recent decades with the aim of producing highly efficient, safe, flexible and robust solar cells to withstand harsh weather conditions. c-Si has been the material of choice in the development of conventional inorganic solar cells owing to it superior properties, abundance and higher efficiencies. However, the associated high costs of Si processing for solar cells have led to a gravitation towards alternative organic solar cells which are cheaper and easy to process even though they suffer from stability and durability challenges. In this work, combination of both inorganic and organic materials to form hybrid solar cells is one of the approaches adopted in order to address the challenges faced by solar cell development.
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Zheng, Wen Ph D. Massachusetts Institute of Technology. "Fabrication of capacitors based on silicon nanowire arrays generated by metal-assisted wet chemical etching." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104114.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 170-177).
Capacitors with high capacitance density (capacitance per footprint area) have potential applications in autonomous microsystems that harvest energy from the environment, as they can store and release energy at high rates. Use of high surface-to-volume ratio structures has been demonstrated as an effective way to increase the electrode area, and therefore to improve the capacitance density, while still keeping the footprint area low. The goal of this thesis was to first develop an understanding of the mechanisms of metal assisted wet chemical etching for fabrication of arrays of silicon nanowires, and then use this understanding to build nanowire array on-chip capacitors in silicon substrates, in order to eliminate additional packaging and enable local and efficient energy delivery. Two types of capacitors were investigated: electrostatic metal-oxide-semiconductor (MOS) capacitors for power management, and supercapacitors for energy storage purposes. For both types of devices, enlarged surface area per footprint was achieved by utilizing the arrays of silicon nanowires. Fundamental studies of the roles of metals in metal-assisted chemical etching (MACE) of silicon were conducted. Lithography techniques were used to generate patterns in metal films which when subjected to MACE resulted in formation of ordered arrays of silicon nanowires. Investigation of various metal catalysts showed that Pt is a more active catalyst than Au, while Cu is not stable in the etchant. Tapered silicon nanowires can be generated by adding a layer of Cu between two Au layers, and etching occurs much faster than when a pure Au catalyst is used. While carrying out research on the mechanisms of MACE, we developed a new electrochemical method for formation of arrays of silicon nanowires, metal-assisted anodic etching (MAAE). In this process, the etchant consists of HF alone, and does not include an oxidant. In both processes, HF is used as an etchant. However, in MACE, electronic holes are supplied through reduction of an oxidant (e.g. H₂O₂), while in MAAE, electronic holes are supplied through an external circuit, with anodic contact to either the metal or the silicon. In both contact cases for MAAE, the metal catalyzes the etching process and leads to controlled formation of silicon nanowires, without the need for an oxidant. This discovery, and its analysis, provided new insights into the mechanisms of both MAAE and MACE, and also opened the possibility for use of metal catalyzed electrochemical etching of other materials that cannot survive the HF/oxidant mixture. Processes for fabrication of on-chip capacitors based on silicon nanowires were next developed. We first fabricated on-chip MOS capacitors with nanowire arrays etched using MACE with both single crystal silicon substrates and polycrystalline silicon films. For wires made in both cases, the capacitance density followed a same scaling trend related to their geometries. Epitaxial wafers were used with a post-etch doping process to reduce the series resistance in the devices in order to obtain a better frequency response, as desired for high frequency circuits. To achieve higher capacitance densities for energy storage purposes, we also designed a solid state supercapacitor device based on nanowires etched using MAAE with heavily doped n-type silicon substrates. The silicon nanowires were coated with RuO₂ using atomic layer deposition (ALD) to achieve a high capacitance. In this case, charge is stored through the formation of an electrical double layer and through reversible redox reactions. We showed that the capacitance density of these devices roughly scaled with the increased surface area of silicon nanowire arrays. The solid state supercapacitor achieved a capacitance density of 6.5mF/cm², which is comparable to the best results achieved with other types of on-chip supercapacitors. In contrast with other processes for forming on-chip supercapacitors, the supercapacitors we demonstrated were fabricated using a fully complementary metal-oxide-semiconductor (CMOS) technology compatible process. Moreover, the Si nanowire-based device achieved this high capacitance density without sacrificing power performance compared to the planar device.
by Wen Zheng.
Ph. D.
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Мадан, Роман Григорович. "Фотоперетворювачі на основі наноструктурованого кремнію." Bachelor's thesis, КПІ ім. Ігоря Сікорського, 2019. https://ela.kpi.ua/handle/123456789/28855.
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Робота складається з 55 сторінок, 4 розділів та містить 35 ілюстрацій, 24 таблиці та 19 джерел в переліку посилань.
Актуальність теми – інтерес до створення гібридних органічних та неорганічних фотоперетворювачів, що мають більш низьку вартість, ніж традиційні.
Метою роботи є дослідження вольт-амперних характеристик фотоперетворювачів. Порівняння характеристик пористого кремнію, отриманого за різного часу травлення.
Об’єкт дослідження – фотоперетворювачі на основі наноструктурованого кремнію.
Предмет дослідження – методи одержання та морфологія наноструктурованого шару оксиду індію й олова, а також плівки меланіну.The work consists of 55 pages, 4 sections and contains 35 illustrations, 24 tables and 19 sources in the list of references. The actuality of the topic is the interest in the creation of hybrid organic and inorganic photoconductors that have a lower cost than traditional ones. The purpose of the work is to study the volt-ampere characteristics of nanostructured silicon solar cells. Comparison of the characteristics of porous silicon obtained at different times of etching. The object of research is nanostructured silicon solar cells. Subject of research - methods of obtaining and morphology of nanostructured layer of indium and tin oxide, as well as melanine films.
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Мадан, Роман Григорович. "Органо-неорганічні гібриди на основі меланіну." Master's thesis, КПІ ім. Ігоря Сікорського, 2020. https://ela.kpi.ua/handle/123456789/38762.
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Актуальність теми – інтерес до створення гібридних органічних та неорганічних тонкоплівкових сонячних елементів, що мають більш низьку вартість, ніж традиційні сонячні елементи.
Метою роботи є визначення оптимальних технологічних умов створення органічно-неорганічних структур для фотовольтаїчного застосування.
Предмет дослідження – органо-неорганічні структури на основі кремнію та меланіну.The relevance of the topic is the interest in creating hybrid organic and inorganic thin-film solar cells, which have a lower cost than traditional solar cells. The aim of the work is to determine the optimal technological conditions for the creation of organic-inorganic structures for photovoltaic applications. The subject of research - organo-inorganic structures based on silicon and melanin.
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Xu, Ying. "Fabrication and Characterization of Photodiodes for Silicon Nanowire Applications and Backside Illumination." University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1446313926.
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Togonal, Alienor. "Silicon Nanowires for Photovoltaics : from the Material to the Device." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX032/document.
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Les cellules solaires à base de nanofils de silicium offrent une alternative intéressante pour la réalisation de panneaux photovoltaïques à haut rendement et à faible coût. Elles bénéficient notamment des excellentes propriétés optiques des nanofils qui forment une surface à très faible réflectivité tout en piégeant efficacement la lumière. Dans cette thèse, nous utilisons et améliorons une méthode de gravure chimique peu coûteuse et industrialisable pour la fabrication de forêts de nanofils de silicium. En adaptant la mouillabilité du substrat et des nanofils, nous avons remédié au problème d'agglomération inhérent à cette méthode lorsqu’on veut obtenir des forêts denses et désordonnées de nanofils. En combinant cette méthode de gravure chimique à la lithographie assistée par nanosphères, nous avons pu fabriquer des réseaux ordonnés de nanofils avec un contrôle précis des propriétés géométriques (diametre des nanofils et distance entre eux). Les propriétés optiques de ces réseaux ont été étudiées théoriquement et expérimentalement afin d'identifier les configurations optimales. Nous avons ensuite fabriqué des cellules solaires à partir de ces différents types de nanofils et deux types de structures. Le premier type, des cellules solaires HIT (Hétérojonction avec couche mince Intrinsèque) à base de nanofils de silicium, a été fabriqué par RF-PECVD. L'optimisation des conditions de dépôt plasma nous a permis d'obtenir des cellules solaires hautement performantes: rendements de 12,9% et facteurs de forme au-delà de 80%. Le second type, des cellules solaires hybrides, est basé sur la combinaison d'une couche organique et des nanofils de silicium. La caractérisation des cellules fabriquées montre des rendements prometteurs. Enfin, nous présentons des résultats préliminaires pour transférer ces concepts à une technologie couches mincesSilicon Nanowire (SiNW) based solar cells offer an interesting choice towards low-cost and highly efficient solar cells. Indeed solar cells based on SiNWs benefit from their outstanding optical properties such as extreme light trapping and very low reflectance. In this research project, we have fabricated disordered SiNWs using a low-cost top-down approach named the Metal-Assisted-Chemical-Etching process (MACE). The MACE process was first optimized to reduce the strong agglomeration observed at the top-end of the SiNWs by tuning the wettability properties of both the initial substrate and the SiNWs surface. By combining the MACE process with the nanosphere lithography, we have also produced ordered SiNW arrays with an accurate control over the pitch, diameter and length. The optical properties of these SiNW arrays were then investigated both theoretically and experimentally in order to identify the geometrical configuration giving the best optical performance. Disordered and ordered SiNW arrays have been integrated into two types of solar cells: heterojunction with intrinsic thin layer (HIT) and hybrid devices. SiNW based HIT devices were fabricated by RF-PECVD and the optimization of the process conditions has allowed us to reach efficiency as high as 12.9% with excellent fill factor above 80%. Hybrid solar cells based on the combination of SiNWs with an organic layer have also been studied and characterized. The possible transfer of this concept to the thin film technology is finally explored
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Wickramasinghe, Thushan E. "Growth Techniques and Optical and Electrical Characterization of Quantum Confined Zero-Dimensional and Two-Dimensional Device Structures." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou156631995093606.
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Tamburi, Marco. "Caratterizzazione della superficie di array di nanofili di silicio." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/6154/.
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Nel primo capitolo viene introdotto lo studio eff�ettuato e descritto un metodo di misure successivo alla caratterizzazione della super�ficie. Nel secondo capitolo vengono descritti i campioni analizzati e, nello speci�fico, la crescita attraverso MaCE dei nanofi�li di silicio. Nel terzo capitolo viene descritto lo strumento AFM utilizzato e la teoria della caratterizzazione alla base dello studio condotto. Nella quarta sezione vengono descritti i risultati ottenuti mentre nelle conclusioni viene tratto il risultato dei valori ottenuti di RMS roughness e roughness exponent.
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Wen, Shu-Ning, and 温書寧. "Silicon Nanostructures Prepared by Metal-assisted Chemical Etching for SERS Application." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/33315625632731698512.
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碩士國立聯合大學
材料科學工程學系碩士班
101
Scientists have distinguished weak Raman signals of molecules from different structures of substances. To enhance the Raman signals, using precious metal nanoparticles such as gold and silver, which can induce the surface plasmon resonance (SPR) by external electric field, has been developed to increase the specimen surface area. This technique is called surface-enhanced Raman scattering (SERS). There are various methods used to produce nanostructures for SERS application. In this study, we applied low-cost metal-assisted chemical etching (MACE) to produce large-surface-area nanowall structures with sub-micron thickness on silicon wafer. After depositing Ag nanoparticles on the 400-nm-thick nanowalls (which is much thinner than the typical thickness from MACE), the enhancement factor (EF) can reach 10^9.
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LEE, WEN-LING, and 李玟怜. "Introducing Current-driving Method to Metal-assisted Chemical Etching of Silicon." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/35mcxh.
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Ko, Pei-Ju, and 柯佩汝. "Thermoelectric properties of silicon nanowires fabricated using metal-assisted chemical etching." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/17597510189977822200.
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碩士國立中央大學
材料科學與工程研究所
103
The thermal conductivity of bulk silicon is 150Wm-1K-1 at room temperature. It is considered as poor thermoelectric material. The ZT is just 0.01 due to its high thermal conductivity. Thus, one dimensional nanostructure has become a good study to solve this problem. Comparing with bulk, there have large surface to volume ratio of one dimension nanostructure. The thermal conductivity reduced by the phonon scattering in the boundary of nanowires. It is helpful to reduce the thermal conductivity. In our study, we use MACE method to fabricate single rough silicon nanowires from lightly doped p-type and heavily doped n-type (100) wafers. The diameter of silicon nanowires are about 150-250nm. The thermal conductivity was decreasing obviously. After oxygen plasma etching, the electric conductivity was increased for lightly doped silicon nanowires.
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Lai, Ming-Hung, and 賴明宏. "Enhanced metal-assisted chemical etching on silicon by localized surface plasma resonance." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/69586029075337167541.
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碩士國立清華大學
光電工程研究所
101
In recent years, since silicon nanostructures have many unique qualities, they have been applied to a wide variety of areas, including optoelectronic devices, biological, semiconductor optical devices, optical-sensing devices and solar cells. In this thesis, metal-assisted chemical etching of silicon incorporating localized surface plasma resonance was studied. The basic idea is that the etching rate is influenced by the light illuminating on the metal nanoparticles. Several case studies were carried out to examine the etching rate, including different content of the chemical etching solution, the vapor chemical etching method, and light sources with different wavelength bands. SEM images are taken to characterize the silicon nanopores, etching rate and so on. Via the experimental results, we concluded the localized surface plasmon (LSP) on the metal nanoparticles will affect the etching rate very much. These strong LSP modes increase the light absorption of Si, resulting in a large amount of holes injected in the silicon. It can explain why the etching speed was greatly enhanced and was wavelength dependent.
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Wang, Po-Sheng, and 王柏盛. "Fabrication and Wettability of gradient porous silicon by silver metal assisted chemical etching." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/v3uw9w.
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碩士國立中央大學
能源工程研究所
107
In recent years, nanoporous silicon plays an important role in the semiconductor industry and energy industry. Two-step metal assisted chemical etching method has the advantages of low cost and simple processes. In biomedical and microfluidic systems, the hydrophobicity of materials must be considered. We can control a fluid drop to move on a solid surface by changing the hydrophobicity of surface material with nano structures. We deposit silver particles with electro-less plating deposition method, followed by the anisotropic etch of the silicon surface by oxidation of etchant and silver particles. We apply different temperature to see how it affects the etching depths and the structures. Appropriate temperature helps to achieve best etching depth and porousity. We also determine the effects of different surface structures on droplet contact angles. We find that the driving force to make the droplet move is too small on the nano porous silicon surface we made. So we use a tilt platform to increase the driving force to observe the effects easily. The critical angle at the larger contact angle side is smaller than the one at the smaller contact angle side, and is faster in the increase of the acceleration of the droplet.
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PAN, XIANG-QIN, and 潘詳親. "Manufacturing and Thermal Property Analysis of Porous Silicon Structure by Metal Assisted Chemical Etching." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/z9zg43.
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碩士國立中央大學
機械工程學系
106
Nanoporous material has been widely used in various applications. It has high area-to-volume ratio that increases surface area and can be used in gas sensors, mass spectrometers, mass-transferring films, and anti-reflection coating on solar panels. Due to the increasing porosity and the size effects of nano-structures, it leads to an effective decreasing in the heat conduction coefficient and makes it a good thermal insulating material. Typical porous silicon fabrication processes include electrochemical etching, dry etching, and metal-assisted chemical etching. Among them, metal-assisted chemical etching has the advantages of simple process and low equipment cost. In this study, we use metal-assisted chemical etching to prepare high aspect ratio nanoporous silicon, explore the relation between etching parameters and porosities, and analyze its heat conduction properties. The silver nitrate solution and hydrofluoric acid were used to form the Ag nanoparticles on silicon surface as the catalyst for etching. The anisotropic etching was performed in the etching solution with hydrogen peroxide to form nanoporous structures. A well-distributed nanoporous structure was achieved through controlling the concentration of hydrogen peroxide. The results showed that for a long etching time, the etching rate became slower and the porous layer growth rate gradually decreased due to the etching on top structure. Different heat transfer models were used to analyze the thermal transfer coefficient. The results showed for the simplified models that do not consider the pore size exhibited a significant difference in thermal conductivity for small pore size samples. Considering of dependence of porosity and pore size in the process perspective, the effective thermal conductivity was lower than expected due to the impact of the small pore size structure.
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Chiu, Chia-Chen, and 邱嘉辰. "Using Metal-assisted Chemical Etching to Enhance the Performance of Silicon Nanopillar Solar Cells." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/22311864266205397470.
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碩士國立聯合大學
材料科學工程學系碩士班
103
In this study we adopted p-type silicon wafers as substrates and used semiconductor technology of lithography and plasma dry etching to produce three different sizes of array structures on the silicon substrate. These array structures were doped with phosphorus to form p-n junction on the surface by ion implantation; the implantation dosage was fixed and the values of implantation energy were varied to seek a suitable parameter for device performance. An aluminum coating was prepared by sputtering as a backside electrode, and silver paste was used as the front side electrode. The performances of array devices were evaluated by a sun light simulator under AM1.5 condition. In the second part of this thesis, we developed a metal-assisted chemical etching to create nanostructures on these array structures, which increased the absorption by lower surface reflection to enhance the photoelectric conversion efficiency of solar cells. Analyses by field emission electron microscopy, total reflectance measurement, and the photoelectric conversion efficiency were carried out in these two parts. The results showed that the in the first part, for three columnar structures with 400, 1000, and 5000 nm, the photoelectric conversion efficiency were 11.33%, 10.35%, 9.36%, respectively, and a columnar array structure with 400 nm feature can be significantly increased 35.85%; in the second part of the wet etching, the result shows that the efficiency of 5000-nm device was improved 5.75% after etching, and for 1000-nm array the efficiency was increased 6.1%.
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Chang, Chia-Feng, and 張家逢. "Optimization of surface treatment after forming black silicon by metal-assisted chemical etching method." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/34354978674950272505.
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碩士國立臺灣科技大學
化學工程系
104
We optimized the condition in metal-assisted chemical etching in order to obtain the lowest reflection of our black silicon. Meanwhile, we also optimized several cleaning methods to obtain black silicon which has low reflection but high minority carrier lifetime. We found that in our condition, reflection won’t get lower as the etching time stays longer. Our black silicon has reflection 4% at 600nm, while the etching time is 135 second. In cleaning part we found that ammonia is not suitable for cleaning black silicon because it causes too much etching to the wafer. Hydrochloric acid and sulphuric acid cause less etching to black silicon. Sulphuric acid has better cleaning ability than the others. We obtained 950μs minority carrier lifetime on our best black silicon and its reflection is 5% (at 600nm). Eventually we apply to KOH textured silicon wafer. We obtained 684μs minority carrier lifetime and reflection 5% at 600nm. Compare with wafers only textured by KOH, we lowered the reflection by 8% and the minority carrier lifetime recovered by 61%.
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Li, Hong Ching, and 李鴻慶. "Fabrication of Multicrystalline Silicon Solar Cells with Surface Texturing by Metal-Assisted Chemical Etching (MAE)." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/60851818079493496075.
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碩士國立清華大學
電子工程研究所
100
In this thesis, the surface texturing for multicrystalline silicon by using metal-assisted chemical etching (MAE) method was carried out to fabricate solar cell. There were two kinds of etchant used in the MAE process. One was a mixture of HF, H2O2 and H2O and the other was a mixture of HF, Fe(NO3)3 and H2O. The metal used in the MAE process was Ag. The textured surface morphologies were analyzed by SEM and reflectance measurement. The different morphologies including bowl, cone and grating with high aspect ratio were fabricated. The average reflectance of textured surface is below 10% and the lowest reflectance is about 2~3% in the range of 400~600 nm. The efficiency of solar cell fabricated with HF/Fe(NO3)3/H2O is 8.24% and fabricated with HF/H2O2/H2O is 11.81%.
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Cheang, Jia-Kang, and 鄭家康. "Fabricating High Aspect Ratio Silicon Micro-Holes Implemented by Metal-Assisted Chemical Etching with Taguchi Analysis." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/24768390488648287008.
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碩士國立清華大學
材料科學工程學系
102
High aspect ratio (AR) Silicon base structure plays an important role in semiconductor industry. Recent advances in small size and multifunctional chip has made the increased demands of fabrication of micro and nano scale high AR silicon structure. However, the commercial fabricating method, deep reactive ion etching (DRIE) suffers from high cost and complex processing due to the high maintenance fees and complicated set up. In contrast, we investigate the ability of promising novel chemical etching, metal assisted chemical etching (MACE) that can etch Silicon (Si) wafer in <100> direction near room temperature and thus benefits from it’s simple and cost effective reaction process. In order to fabricate high AR silicon micro holes structure, we have optimized our MACE recipe by employing statistical Taguchi L9 method and ANOVA analysis. Subsequently, the post-MACE formed Si wires have been removed by furnace oxidation followed by Hydrofluoric acid (HF) treatment. Therefore, high AR Si micro holes structure with smooth surface is obtained. Our results demonstrate that the AR value is up to 13 (for 4x4um square arrays in p-type (100) Si substrate), and the etching rate of optimal condition is about 3 µm/min. Moreover, an alternative method that possess larger throughput for fabricating high AR Si micro structure has been performed. Besides, it is believed that the AR value can be further improved by increasing the thickness of Si nitride layer (protection layer), using stronger protection layer instead, and exploring the method that can well-control the morphology of metal catalyst which strongly influence the post-etched structure.
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"Analysis of convective mass transfer during electrochemical metal plating and etching using a linear overpotential relaxation technique." Tulane University, 1992.
Find full textAbstract:
A linear overpotential relaxation technique has been used successfully to determine liquid-phase mass transfer boundary-layer thicknesses and salt film thicknesses during electrochemical metal plating and etching. This method was tested and verified for iron and copper dissolution from a rotating disk, copper deposition at a rotating disk in the presence of additives, and mixed natural and forced convection copper deposition at a segmented vertical flat plate. For both anodic dissolution and cathodic deposition processes experimentally measured concentration overpotentials were found to decay linearly with respect to the square-root of time immediately after current interruption. A mathematical model, which was derived by combining the solution to Fick's Second Law of diffusion with the Nernst equation, predicted this linear overpotential decay behavior. Liquid-phase mass transfer boundary-layer thicknesses and salt film thicknesses were computed by matching short-time overpotential decay data to the mathematical model Liquid-phase mass transfer boundary-layer thicknesses during active and transpassive iron etching were in good agreement with those predicted by the Levich equation. The thickness of prepassive FeSO$\sb4$ salt films were found to be dependent on the disk rotation speed and anode potential. Liquid-phase effective mass transfer boundary-layer thicknesses during active copper dissolution were found to be $\sim$56% smaller than those during cathodic deposition. Steady-state prepassive CuSO$\sb4$ film thicknesses were dependent on 1/3 power of the anode potential and $-$1/3 power on the disk rotation speed Liquid-phase effective mass transfer boundary-layer thicknesses during copper deposition with Selrex Cubath and Cl$\sp-$ addition agents were found to be equal to those for an additive free case. Mass transfer boundary-layer thicknesses for an electrolyte containing Copper Gleam-PC and Cl$\sp-$ addition agents were found to be smaller than those predicted by the Levich equation at low disk rotation speeds and applied currents A Sherwood number correlation for currents below and near the limiting current was derived for mixed assisting natural and forced convection copper plating. During opposing natural and forced convection flows the flow pattern at the top and the bottom edges of the plate were found to be laminar at all forced convection velocities. The fluid velocity over the remaining portion of the electrode was found to be turbulentacase@tulane.edu
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Tsao, Chiao-Heng, and 曹巧姮. "Fabrication of Silicon Nanowire Array Through the Metal-induced Wet Chemical Etching Method and Its Photovoltaic Properties." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/87917143123478414382.
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碩士國立清華大學
材料科學工程學系
99
Large area SiNW arrays were successfully prepared by immersing a silicon wafer into an aqueous solution of AgNO3 and HF in an electroless metal deposition (EMD) process. However, in the process the Ag clusters easily aggregated, forming large Ag particles of various sizes, which in turn resulted in silicon wires with a large size distribution. To improve the uniformity of the SiNW arrays, uniform dispersed gold nanoparticles were used as the cathode instead, followed by the etching process using H2O2/HF solution. The growth conditions, morphologies and anti-reflection properties of SiNW arrays have been studied. Ultraviolet-visible spectroscopy analysis reveals that the SiNW has remarkable anti-reflection property, as compare with the plane silicon wafer. The reflectance of SiNW is found to decrease with increasing reaction time. The simple, inexpensive and easily scalable process to fabricate a large area silicon anti-reflection surface is a promising process for silicon-based solar cell. We used the synthesized SiNWs to fabricate solar cells. According to current-voltage curve and monochromatic incident photon-to-electron conversion efficiency(IPCE) analysis, we knew that there are many defects on the SiNW surface, which can act as recombination centers and enhance the surface recombination rate. Therefore, only the SiNW solar cell with appropriate length, which is enough to trap light but not too long for cause serious recombination, shows better performance than planer-Si solar cell.
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Chang, Cheng-Ping, and 張振平. "Evalution and Control of Chemical Hazards for the Preventive Maintenance of Metal Etching Machine in Wafer Factories." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/37244180499445436969.
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博士國立臺灣大學
環境衛生研究所
88
There are three major parts in this study, first, to establish a set of ambient monitoring method for hazardous materials in semi-conductor wafer factories. Second, by adopting method mentioned above to evaluate chemical hazards for metal etching process during preventive maintenance. Finally, to find an effectively feasible control strategy based on results obtained from the second step. An automatic Furiour transform infrared meter, which can make a multi-compound, real-time, and continuous monitor, has been improved and assembled for suitability in semi-conductor plant during this study. Use the combination of autosampling controller and vaccum pump, which have the characteristic of decreasing the interference of former sample, ensuring the stability of FTIR, and also relied on interface program, the instrument make quality and quantity analysis simultaneously. It was validated by this study. According to measuring results, it showed that periodical peak exposures were detected by FTIR and the ceiling value in breathing zone can reach 91ppm, when de-ionized water or isopropyl alcohol was used to clean up the reaction chamber during preventive maintenance of metal etching. If nitrogen gas existed, hydrogen cyanide gas was detected and an instantaneous ceiling value 72ppm can be found in breathing zone. In both situations above mentioned, the peak exposures were higher than the Permissible Exposure Limits-Ceiling. The maximun concentraction of hydrogen chloroide was 90 ppm in breathin zone, and the concentration of hydrogen cynaide was 65ppm. It was believed that plasma can accelerate the chemical reaction of chloride and aluminum, in result, the aluminum chloride was produced and further reacted with water to generate hydrogen chloride while maintenance was proceeded. Through the similar mechanism, plasma accelerated the reaction of carbon and nitrogen, then the cyanide compounds reacted with acid to generate hydrogen cyanide. Because, the concentration of hydrogen chloroide and hydrogen cynaide was so high, the workers have to work with breathing appartus. To reduce these toxic gas at metal etching machine work place, specially, during preventive maintenance procedure. We proposed a newly designed local ventilation system to capture the hazard chemicals, which is followed the concept of high speed and low volume. We used the transparent acrylic material to make the hood body. A piece of transparent PVC materal (thickness 2mm) is cut into 10 parts from the center to the edge, which is fixed on the top of the hood. The capture velocity of this system is 10-15 m/s. this system was validated in this study, and adept by the wafer factories as a standard equipment for the preventive maintence of metal etching machine.
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Wu, Zong Hua, and 巫宗華. "Fabrication of Complex Micro- and Nanostructures using Self-Assembled Diblock Copolymer Templates and Metal-Assisted Chemical Etching." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/63834465506078938528.
Full textAbstract:
碩士國立清華大學
工程與系統科學系
103
This thesis presents a novel integration scheme that can fabricate complex micro-nano hybrid silicon structures. The structures are formed by metal-assisted chemical etching, while microlithography and self-assembled diblock copolymer nano- templates are employed to define their geometries. The nano-templates are made of P(S-b-MMA) copolymer that can self-assemble into arrays of 18-nm-diameter PMMA cylinders hexagonally packed in a PS matrix with a lattice constant of 36 nm. To facilitate the self-assembly process, a thin layer of 3-(p-methoxy-phenyl)propyl- trichloro-silane is coated between P(S-b-MMA) and silicon substrate. Once PMMA is selectively removed, the resulting nanoporous PS film is employed to control the deposition of metal nanodots. In the prototype demonstration either chromium or gold is deposited, while chromium and gold is used as the blocking and catalytic material in the etching process, respectively. Meanwhile, photolithography is employed to realize the micro-patterning of metallic thin films. Throughout the process, reactive ion etching is used repeatedly to clean the substrate surface. Finally, the gold-assisted chemical etching is carried out in a solution consisting of deionized water, H2O2, and HF to produce the desired micro-nano hybrid silicon structures. It is demonstrated that the presented integration scheme is a highly repeatable method to form well-aligned, crystalline silicon nanowires with tunable diameters below 100 nm and microstructures as well. As such, the presented integration scheme can fabricate complex micro-nano hybrid structures, which are desired for a variety of cooling and biological applications.
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Sheng-ChiaYu and 尤勝加. "Metal-assisted Chemical Etching of High Aspect Ratio Silicon Nanostructures for Highly Efficient Capture of Bladder Epithelial Cancer Cells." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/bnmss5.
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Tsai, Po-Hung, and 蔡帛宏. "Performance Characterization of Si Thin-Film Solar Cells Using Nanopores Surface Structure on the Emitter Layer by Metal-Assisted Chemical Etching." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/262mb9.
Full textAbstract:
碩士國立臺北科技大學
光電工程系研究所
102
In this work, the optical and electric properties of silicon thin film solar cell with the nanopores subwavelength structures using metal-assisted chemical etching (MACE) and various TiO2 passivation layers are studied. The experiment is first prepared silicon thin film solar cell, The epitaxial layer consisted of a 5-um N--Si base layer and a 0.87 um P+-Si emitter layer grown on N+-Si substrated by chemical vapor deposition (CVD) system. After cleaning, a 20 nm silver film was deposited on the cells surface by E-beam evaporation and annealed at 300 ℃, 5 min on RTA chamber. Then, the nanopores surface structure on the emitter layer was created by using MACE processing under different etching time. Using SEM images to examine the nanopores state and depth on silicon surface, the optical reflectance, dark and photo I-V, EQE were measured and compared. The reflectance of the fabricated 30s MACE time solar cell is less than 2.5% at 350 – 1050 nm wavelength. The maximum conversion efficiency enhancement of approximately 43% (from 5.64 to 8.07%) was obtained for cell with 10s MACE time, the EQE cutoff point at short wavelength band are exhibited a red shifted (from 375 to 420 nm) when the MACE time increased. Finally, different thickness of the TiO2 passivation layer were deposited on the nanopores of the silicon thin film solar cells, in order to reduce its surface carrier recombination and increase the photocurrent. Dark I-V measurement shows that the idealily factory (n) and saturation current (I0) will reduce with TiO2 the thinkness of incresing. For reflectivity measured, the results are: (1) For bare cell and the Cell with 1s MACE time, the reflectance decreases with the thickness of TiO2 increased, like to a single anti-reflective layer on a device. (2) For MACE time of 5, 10, 15, 30 seconds, the reflectivity decreases when a 15 nm TiO2 deposited; the reflectance will increase when the film thickness of 45 nm TiO2 deposited, particullary at 350 to 650 nm wavelength. For EQE and photonvoltaic I-V measurement, the results are: (1) EQE increases with reflectivity decreased. (2) EQE enhance at short wavelength for bare cell and cell with MACE time of 1s was obtained, when the cell deposited TiO2 layer. However, EQE enhanced at long wavelength for cell with MACE time of 5s、10s、15s、30s. Finally, we demonstrated a thin-film Si solar cell with MACE time of 15s and 30 nm TiO2, having the efficiency enhancement of approximately 73.2 % (from 5.64 to 9.77%).