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Chaudhury, Rabib. "Selective wet chemical etching of erosion resistant coatings from titanium alloy substrates: mechanism and optimization." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117073.
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Titanium aluminum nitride (TiAlN) is a type of erosion resistant ceramic coating that is applied to metal parts subject to high wear environments. Adding this coating helps protect the underlying substrate from these adverse conditions. Sometimes the coating layer must be removed and a new layer re-applied. The overarching goal of this project is to successfully remove the TiAlN coating from titanium alloy substrates through wet chemical etching. In meeting this goal, the following objectives must be met: the process must be fast, selective (i.e. does not adversely affect the underlying substrate), operate isothermally, and make use of chemicals that are environmentally friendly. A combination of hydrogen peroxide, potassium oxalate, and ethylenediaaminetetracetic acid (EDTA) was found to accomplish the stated objectives. Hydrogen peroxide and potassium oxalate are responsible for removing the coating and producing titanium metal ions in solution. The role of EDTA is to form coordination complexes with these metal ions so as to reduce their reactivity with hydrogen peroxide in solution. The etching process was optimized for selectivity. A kinetic model was built using a modified differential technique and Arrhenius plots. It was determined that selectivity increases with increasing temperature and potassium oxalate concentration while it decreases with increasing hydrogen peroxide concentration. Sensitivity analysis shows that selectivity is much more prone to change with changing hydrogen peroxide concentration. Surrogate modeling using a Least Squares-Support Vector Machine model confirms the trends predicted by the kinetic model except that selectivity seems to peak when varying potassium oxalate concentration.Titanium aluminum nitride (TiAlN) est un type de revêtement céramique résistant à l'érosion qui est appliqué à des pièces métalliques soumises à des environnements à forte usure. L'ajout de ce revêtement permet de protéger le substrat de ces conditions défavorables. Parfois, la couche de revêtement doit être retiré et une nouvelle couche réappliqué. L'objectif principal de ce projet est de réussir à enlever le revêtement TiAlN à partir de substrats en alliage de titane par 'wet chemical etching'. Pour atteindre cet objectif, les objectifs suivants doivent être atteints: le processus doit être rapide, sélective (c'est à dire ne pas nuire au substrat titanium), de s'opérer dans une manière isotherme, et faire usage de produits chimiques qui sont respectueux de l'environnement. Une combinaison de hydrogen peroxide, potassium oxalate et de l'acide ethylenediaaminetetracetic (EDTA) a été trouvé pour atteindre les objectifs. Hydrogen peroxide et de potassium oxalate sont responsables de l'élimination du revêtement et produire des ions métalliques de titane en solution. Le rôle de l'EDTA est de former des complexes de coordination avec ces ions métalliques de manière à réduire leur réactivité avec le hydrogen peroxide en solution. Le processus a été optimisé pour la sélectivité. Un modèle cinétique a été construit en utilisant une méthode différentielle modifiée et des parcelles d'Arrhenius. Il a été déterminé que la sélectivité augmente avec la température et la concentration de potassium oxalate alors qu'il diminue quand la concentration de hydrogen peroxide augmente. L'analyse de sensibilité montre que la sélectivité est beaucoup plus enclin à changer avec la concentration de hydrogen peroxide. Modélisation de substitution (Surrogate Modeling) en utilisant un modèle Least Squares-Support Vector Machine confirme les tendances prédites par le modèle cinétique, sauf que la sélectivité semble culminer en variant la concentration d'oxalate de potassium.
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Sudirham, Janivita Joto. "Space-time discontinuous Galerkin methods for convection-diffusion problems application to wet-chemical etching /." Enschede : University of Twente [Host], 2005. http://doc.utwente.nl/50890.
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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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Jain, Rahul. "Formation of Aminosilane and Thiol Monolayers on Semiconductor Surfaces and Bulk Wet Etching of III--V Semiconductors." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/255196.
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Continuous scaling down of the dimensions of electronic devices has made present day computers more powerful. In the front end of line, the minimum lateral dimensions in a transistor have shrunk from 45 nm in 2007 to 22 nm currently, and the gate oxide film thickness is two to three monolayers. This reduction in dimensions makes surface preparation an increasingly important part of the device fabrication process. The atoms or molecules that terminate surfaces function as passivation layers, diffusion barriers, and nucleation layers. In the back end of line, metal layers are deposited to connect transistors. We demonstrate a reproducible process that deposits a monolayer of aminopropyltrimethoxysilane molecules less than one nanometer thick on a silicon dioxide surface. The monolayer contains a high density of amine groups that can be used to deposit Pd and Ni and subsequently Co and Cu to serve as the nucleation layer in an electroless metal deposition process. Because of the shrinking device dimensions, there is a need to find new transistor channel materials that have high electron mobilities along with narrow band gaps to reduce power consumption. Compound III--V channel materials are candidates to enable increased performance and reduced power consumption at the current scaled geometries. But many challenges remain for such high mobility materials to be realized in high volume manufacturing. For instance, low defect density (1E7 /cm²) III--V and Ge on Si is the most fundamental issue to overcome before high mobility materials become practical. Unlike Si, dry etching of III-V semiconductor surfaces is believed to be difficult and uncontrollable. Therefore, new wet etching chemistries are needed. Si has been known to passivate by etching in hydrofluoric acid, but similar treatments on III--Vs are known to temporarily hydrogen passivate the surfaces. However, any subsequent exposure to the ambient reoxidizes the surface, resulting in a chemically unstable and high defect density interface. This work compares old and new wet etching chemistries and investigates new methods of passivating the III--V semiconductors.
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Fraser, Michael John. "Optical Fiber Microstructures for Self-Contained Whispering Gallery Mode Excitation." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/73659.
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Optical resonators, which confine light by resonant recirculation, serve as the basis for a wide variety of optical components. Though they appear in many geometric forms, the most effective of optical resonators show axial symmetry in at least one dimension. A popular variation that finds broad application is the dielectric sphere. Acclaimed for their high quality (Q) factor and small modal volume, spheres owe credit of these attractive features to their support of whispering gallery mode (WGM) resonances. The sensitivity of a resonance's frequency and Q to strain, temperature, and other parameters of the surrounding medium can be the basis for ultracompact modulators and sensors.
Physically, WGMs are special optical modes which can be understood as light rays that orbit the equator of the sphere guided by total internal reflection. Like a smooth stone can be skipped along the surface of a pond, light can be confined to the inside of a sphere by successive reflections. To best excite WGMs, the source light should initially trace a line tangent to the sphere's circumference. But incorporating a tiny sphere with such nanometric tolerances into a practical sensor structure has its challenges and the prospects for microsphere applications have suffered because of the plight of this problem.
The work in this dissertation details the fabrication and function of three new "press fit" spherical resonators. These etched fiber micro-devices were developed to meet the demand for a robust, self-integrated means of coupling light between an optical fiber and WGMs in a microsphere resonator. The etching processes have been tuned to enable secure storage of a microsphere while also providing efficient excitation and interrogation of WGMs. Furthermore, the methods have been designed to be staightforward, quick, and repeatable. Using standard etchants on common polarization-maintaining fiber with readily purchased microspheres, the press fit resonators demonstrated here can be batch-fabricated and assembled. The press fit spherical resonator offers an alignment-free and conveniently pigtailed WGM coupler that has great potential for bio-science sensing applications and studies of resonant bispheres.Ph. D.
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Patzig-Klein, Sebastian. "Untersuchungen zum Reaktionsverhalten kristalliner Siliziumoberflächen in HF-basierten Ätzlösungen." Doctoral thesis, TU Bergakademie Freiberg, 2009. https://tubaf.qucosa.de/id/qucosa%3A22706.
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Die vorliegende Arbeit befasst sich mit der grundlegenden Untersuchung von Reaktionsmustern kristalliner Si-Oberflächen in HF-basierten Lösungen. Ausgehend von den industriell genutzten HF-HNO3-H2O-Gemischen wurden wisher wenig untersuchte HF/HNO3-Konzentrationsverhältnisse, die durch gelöste Stickoxide bedingten Folgereaktionen sowie der PH-Wert als Steuerparameter zur Aufarbeitung feinkörniger Si-Rohstoffe (Korngröße ≤ 0,5 mm) identifiziert. Die in diesem Kontext zentrale Rolle der NO+-Ionen wurde durch Untersuchung der spezifischen Reaktionsmuster an kristallinen as-cut und hydrophobierten Si-Oberflächen sowie bei Umsetzungen mit Oligosilanen als Modellverbindungen bestätigt. Die aus den umfassenden analytischen Daten (FT-IR-, Raman-, NMR-Spektroskopie, IC, REM-EDX, AFM) gewonnenen Erkenntnisse liefern einen wichtigen Beitrag zum Verständnis nasschemischer Halbleiterätzprozesse und erschließen neue Anwendungsfelder.
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Patzig-Klein, Sebastian. "Untersuchungen zum Reaktionsverhalten kristalliner Siliziumoberflächen in HF-basierten Ätzlösungen." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2010. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-27118.
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Die vorliegende Arbeit befasst sich mit der grundlegenden Untersuchung von Reaktionsmustern kristalliner Si-Oberflächen in HF-basierten Lösungen. Ausgehend von den industriell genutzten HF-HNO3-H2O-Gemischen wurden wisher wenig untersuchte HF/HNO3-Konzentrationsverhältnisse, die durch gelöste Stickoxide bedingten Folgereaktionen sowie der PH-Wert als Steuerparameter zur Aufarbeitung feinkörniger Si-Rohstoffe (Korngröße ≤ 0,5 mm) identifiziert. Die in diesem Kontext zentrale Rolle der NO+-Ionen wurde durch Untersuchung der spezifischen Reaktionsmuster an kristallinen as-cut und hydrophobierten Si-Oberflächen sowie bei Umsetzungen mit Oligosilanen als Modellverbindungen bestätigt. Die aus den umfassenden analytischen Daten (FT-IR-, Raman-, NMR-Spektroskopie, IC, REM-EDX, AFM) gewonnenen Erkenntnisse liefern einen wichtigen Beitrag zum Verständnis nasschemischer Halbleiterätzprozesse und erschließen neue Anwendungsfelder.
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Lippold, Marcus. "Beiträge zum Verständnis des sauren nasschemischen Ätzens von Silicium." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2014. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-145077.
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Der Siliciumauflöseprozess in HF-HNO3-H2SO4/H2O-Lösungen unterscheidet sich vom Ätzprozess in HF-HNO3-H2O-Standardmischungen in Bezug auf die Reaktivität gegenüber Silicium, erzielte Oberflächenmorpholgien sowie die beim Ätzen entstehenden gelösten und gasförmigen Produkte. Durch die Behandlung in H2SO4-reichen HF-HNO3-H2SO4/H2O-Lösungen werden auf Siliciumwafern Texturen mit hoher Rauigkeit und geringer Reflexion erzeugt. mc-Si-Solarzellen texturiert durch eine H2SO4-reiche Ätzlösung weisen vergleichend zu Solarzellen mit Standardtexturen höhere Wirkungsgrade auf. In HF-HNO3-H2SO4/H2O-Lösungen mit hohen Schwefelsäurekonzentrationen (c(H2SO4) > c(H2O)) wirkt sowohl das Salpetersäuremolekül HNO3 als auch das Nitrylion NO2+ als Oxidationsmittel. Trifluorsilan HSiF3 und Hexafluordisiloxan F3SiOSiF3 wurden erstmalig als gasförmige Produkte des sauren nasschemischen Ätzens identifiziert. Anhand von Modellreaktionen zur Reaktivität von Nitrylionen wurde deren Reduktionssequenz im Siliciumätzprozess aufgeklärt.
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Röper, Stephanie. "Strukturuntersuchungen an biologischen Materialien mit Hilfe rasterkraftmikroskopiebasierender Nanotomographie." Doctoral thesis, Universitätsbibliothek Chemnitz, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-68803.
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Ziel ist die räumliche Abbildung biologischer Materialien (Knochen, Kollagenfibrillen und Zähne) hinsichtlich deren Struktur auf der Nanometerskala mit Hilfe der Nanotomographie. Die Nanotomographie ist eine moderne dreidimensionale Volumenabbildungsmethode auf der Nanometerskala basierend auf der Rasterkraftmikroskopie. Für die Nanotomographie wurden Ätzprotokolle an Zähnen, Kollagenfibrillen und Knochen entwickelt, die einen gleichmäßigen Abtrag bewirken. Lineare Verschiebungen der aufgenommenen Schichten werden mit Hilfe der manuellen Registrierung korrigiert und zu einem Volumenbild rekonstruiert. Ein zentrales Ergebnis sind dabei erste hochaufgelöste Volumenbilder einzelner Kollagenfibrillen im nativen Knochen. Neben der konventionellen Nanotomographie wird ein Ansatz zur automatisierten Nanotomographie mit einer Auflösung von 10 nm am Beispiel des menschlichen Knochens und Zahnes demonstriert. Mit Hilfe von mikroskopischen und elektronenmikroskopischen Techniken wurden die verschiedenen Strukturebenen des humanen Zahn und Knochens abgebildet und die räumlichen Strukturen der TM-AFM-Bilder auf der Mikro- und Nanometerskala eingeordnet. Darüber hinaus konnte mit Hilfe analytischer Messmethoden die chemische Zusammensetzung des kortikalen nativen Knochens erfasst werden und Änderungen durch das Ätzen detektiert werden.
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Lai, Yung-Yu, and 賴永裕. "The Study of Chemical Wet Etching on GaN Epi-layer." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/86721184869275920065.
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碩士淡江大學
化學工程與材料工程學系碩士班
101
This study use the different etchants to do wet-etching process on the un-doped GaN epi-layer on sapphire substrate. We investigate in detail about the depth and morphology by different etching conditions. In this experiment, metal-organic chemical vapor deposition (MOCVD) was used to regrow un-doped GaN on sapphire substrate. And then, c-plane GaN epi-layer was used to the basic substrate for etching study. The different polarities face have respective phenomenon in etching process. Therefore, this study will discuss the different etching behaviors of GaN epi-layer. Finally, we found that molten KOH will etch the plane of (101 ¯2) and (101 ¯1 ¯ ) at 180°C. The etching will get more energy to do shrinkage, when we enhance the temperature to 260°C, and then the plane will change to (11 ¯00) and (101 ¯1 ¯ ). The H3PO4 will etch the plane of (11 ¯00) and (101 ¯1 ¯ ) at 180°C and 260°C. And then, the H3PO4+H2SO4 will etch the plane (101 ¯1 ¯ ) only at 180°C and 260°C.
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Li, Shao-Huang, and 李劭皇. "Study on Selective Wet-chemical Etching for GaSb and InAsPSb." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/30247397869814890676.
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碩士國立臺灣大學
電子工程學研究所
101
In this thesis, a series of InAsPSb with different composition was grown on (100) n-type GaSb substrate by a GSMBE system. In order to find a selective wet-chemical etchant, we study the characteristics of hydrochloric acid-based and hydrofluoric acid-based solutions etchant for InAsPSb and GaSb. For hydrochloric acid-based solution, the influence of oxidizing agent on etch rate was studied. We found that etching rate of GaSb with hydrochloric acid-based solution is a linear function of the volume H2O2. Besides, we investigate the dependence between the etch rate, temperature and composition of InAsPSb. For hydrofluoric acid-based solution, we also investigate the dependence between the etch rate and composition of InAsPSb. Furthermore, we found there is significant selectivity about 159.75 between GaSb and InAs0.48P0.36Sb0.16, indicating that solution will be very useful in the fabrication of devices based on InAsPSb/GaSb heterostructure. Then we successfully fabricated a microdisk structure by using the hydrofluoric acid-based solution.
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Lin, Chun-Hung, and 林俊宏. "Wet chemical etching study of galliun nitride by acid solution." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/84eb34.
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碩士中正理工學院
應用化學研究所
88
Since GaN has the wide band gap of 3.5eV (wurtzite phase), it is suitable for the light-emitted diodes, laser diodes, and the other photoelectric components, which emits the blue-green lights. Etching method and optimum are two important procedures to prepare the photoelectric components of the GaN device. The energetic ion etching and wet etching the are primary etching methods at the present time. Techniques like plasma of active gas or energetic ion etching can etch a smooth bottom and a vertical sidewall. However, the surface damage caused by ion bombardment will impact the device performance. On the other hand, the crystal structure and the chemical characteristic of GaN are stable, but not easy etching. This study selects H3PO4 solution with a high temperature and the photo-enhanced etching method to perform wet chemical etching. The temperature was heated up to 180℃ in H3PO4 solution (85%) to produce etching and to investigate the relationship between etching parameters and surface defects. The photo-enhanced chemical etching technique was developed by using a He-Cd laser as the light source. This thesis discusses the relationship among etching photo-current, etching time, etching rate, different consistency, and thermal pretreatment by different gases. The experimental results show that the best etching rate at pH value is 1.14. When the hydrogen gas passes through the GaN layer, the gas increases the etching rate. However, an opposite result is observed when hydrogen gas is replaced by nitrogen gas.
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MIAO, JIN-RU, and 苗金儒. "Computer simulation of morphological formation and evolution during wet chemical etching." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/13124553219793787290.
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碩士國立臺南大學
材料科學系碩士班
105
The technique of wet chemical etching has been applied in many fields, especially in semiconductor industry, due to its low cost, convenience, and controllability. With the decrease in the size of the electronic devises, the precise fabrication of complicated patterns and morphologies on a smaller chip has become an important issue. In order to manufacture a specific morphology suitable for the functional devices, all the processing parameters, such as the species, concentration and temperature of the etchant, need to be well controlled. In this study, a chemical etching model based on a phase field approach was established to simulate the evolution of surface morphology during the etching process. By controlling the experiment parameters such as the reaction rate, temperature, and concentration of etchant in the numerical model, the effect of formation and evolution of surface morphology can be realized. Furthermore, to simulate the real situation of the real substrate more accurately, we introduced the surface defects into the model to investigate the morphological variations due to the density of defects during wet chemical etching. A numerical simulation of the metal assisted chemical etching (M.A.C.E.) was also included in this research. In the theoretical calculations of M.A.C.E., several parameter, for instance the particle size, the amount of particles, and the array of particles, were tailored to demonstrate the influence on the formation and evolution of surface structures. Finally, a simple mask compensation design was applied to avoid undercutting. With these results simulated by phase field model, a better understanding on the underlying mechanisms of morphological formation and evolution during wet chemical etching process was provide in this study.
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Hsu, Chew-Wei, and 許晁瑋. "InGaN based MSM Photodetectors Fabricated by Photoenhanced Chemical Wet Etching Technique." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/34099709980978028301.
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碩士國立成功大學
奈米科技暨微系統工程研究所
96
Wild band gap material such as III-V compound are attracted in well electronic property of high chemical stability, high mobility, high thermal stability, and high breakdown voltage. The structure of InGaN based MSM photodetectors are epitaxied on sapphire substrate by MOCVD system. As result of the high lattice mismatch between InGaN and sapphire, the epitaxal quality is poor. Thus, the objective of this research is to design the appropriate device structure for InGaN based MSM, MOS, and heterojunction PDs to improve the device performance. On the other hand, InGaN based PDs with the recessed electrode is fabricated by PEC etching technique. Expectably, the device performance of recessed electrode PDs will be enhanced by the uniform electric field. For the experiment one, the dark current of MSM PDs is very high due to the poor expitaxal quality. Then, InGaN based MOS PDs are fabricated in order to decrease the dark current. At a bias of 3 V, the photocurrent to dark current contrast ratio of InxGa1-xN (x=0.37, 0.60, and 0.85) is about 6.7, 10.7, and 47.9, respectively. However, the photocurrent to dark current contrast ratio of MOS PDs is only 1~2 times higher than MSM PDs that is due to the oxide layer decreases both of photocurrent and dark current in the meantime. Therefore, the thin SiO2 film is replaced with α-Si to enhance the photocurrent to dark current contrast ratio. For the Pt/α-Si /InxGa1-xN (x=0.37, 0.60, and 0.85) heterojunction PDs, the dark current is about 10-7 ~10-8 A, and the photocurrent to dark current contrast ratio is 84.8~194.3 times larger than MSM PDs, and the cut-off wavelength is 470, 640, and 810 nm, respectively. Then Schottky barrier height is measured about 0.92, 0.76, and 0.69 eV, respectively. The Pt/α-Si contact is confirmed to improve the performance of the InxGa1-xN (x=0.37, 0.60, 0.85) based heterojunction PDs. For the experiment two, the recessed electrode MSM PDs is designed to enhance the device performance by the uniform electric field. The recessed electrode PDs is fabricated by the PEC etching technique, and the roughness of active layer is 31 % lower than as-grown material, which means the etching damage is low. For Pt/InxGa1-xN (x=0.37, 0.60, and 0.85) recessed electrode MSM PDs, the photocurrent to dark current contrast ratios are 480.6, 228.8, and 2208.7, respectively. It is found that the improvement of the photocurrent to dark current contrast ratios are 55.8~94.4 times higher for recessed electrode MSM PDs than planar MSM PDs. Compared with the ICP etching technique, it is found that the improvement of the photocurrent to dark current contrast ratio by PEC technique is 2.66 times higher than ICP process. Therefore, the design for recessed electrode MSM PDs by PEC etching is confirmed to enhance the device performance.
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Yu, Wan-Ting, and 游菀婷. "Research on Chemical Wet Etching and Polishing and Surface Roughness of AT-cut Quartz Wafer." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/96859261528062193704.
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碩士國立彰化師範大學
機電工程學系所
104
In recent years, the need of consumer electronics increases because of industrial demand, and furthermore, effects the requirement of oscillators. Quartz crystal oscillator can get accurate clock signal with the piezoelectric effect oscillation. The range of oscillation frequency, which is made by quartz wafer, is from MHz to several hundred MHz, and the mode of oscillation is TSM (Thickness Shear Mode). However, in a traditional fabrication was based on mechanical cutting and polishing process, which is difficult to increase the oscillation frequency anymore. Therefore, a novel process was propose in this research. In this research, using the chemical wet etching and polishing process to reduce the thickness to reach the ideal oscillation frequency, 60MHz, and discussed the surface roughness of AT-cut quartz wafer for depicting the frequency response characteristics. In his research, a novel notion of etching and polish was proposed. In the process of etching and polish, the ultrasound was used to enhance the effect of etching and the fluidity of polish solution. Compared the process with stirring magnet, we used the conditions, first soaked the wafer in mixed solution of HF (49%) and NH4F (40%) or 36℃ HF (23%) for two hours, and then soaked in the solution of 36℃ HF (11.5%) for one hour. After the polishing process, we use the WYKO NT-2000 non-contact optical profiler to measure the surface roughness of AT-cut quartz wafer, and using the ViTiny UM06 electron microscope to measure the thickness. Form the measurement data, the etching rate and oscillation frequency can be clearly explain. Finally, use the HP AgilentE5100B high speed network analyzer to measure the oscillation frequency and frequency characteristics. After the process of polishing and chemical wet etching, we can find the best experimental parameters, which is using 36 ℃ HF (23%) for etching with ultrasonic vibration and 36 ℃ HF (11.5%) for polishing. The surface roughness can reach 53.1 nm, and the transparency is relatively better. In the Frequency response characteristics, the main frequency is more obvious, and the least parasitic frequency. The real oscillation frequency is 33.38 MHz, it has 3.98MHz error with the formula. We can have the AT-cut quartz wafer with better roughness, transparency, and less spurious by adjusted the experimental and theoretical parameters.
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Skolo, Kholiswa Patricia. "Controlled wet-chemical dissolution of simulated high-temperature reactor coated fuel particles." Diss., 2012. http://hdl.handle.net/2263/29908.
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High-temperature reactors make use of tri-structural coated fuel particles as basic fuel components. These TRISO particles consist of fissionable uranium dioxide fuel kernels, about 0.5 mm in diameter, with each kernel individually encased in four distinct coating layers, starting with a porous carbon buffer, then an inner pyrolytic carbon (IPyC) layer, followed by a layer of ceramic silicon carbide (SiC) and finally an outer pyrolytic carbon layer (OPyC). Collectively, the coating layers provide the primary barrier that prevents release of fission products generated during burn up in the UO2 fuel kernel. It is crucial to understand how the fission products contained within the fuel interact with the coating layers and how they are distributed within the fuel. The first step commonly performed to obtain the information on distribution is removal of the coating layers. The purpose of this study was to investigate the possible use of wet chemical etching techniques with the aim of removing the coating layers of ZrO2 coated fuel particles in a controlled way and to establish experimental parameters for controlled dissolution of irradiated fuel particles. Stepwise dissolution of coated fuel particle coating layers, containing zirconia kernels has been investigated by chemical etching experiments with acidic solutions of different mixtures. The heating methods used include heating by conventional methods, hot plates and a muffle furnace, a reflux-heating system and microwave-assisted digestion. The etching mixtures were prepared from a number of oxidizing acids and other dehydrating agents. The capability of each reagent to etch the layer completely and in a controlled manner was examined. On etching the first layer, the OPyC, the reflux heating method gave the best results in removing the layer, its advantage being that the reaction can be carried out at temperatures of about 130 ºC for a long time without the loss of the acid. The experimental results demonstrated that a mixture composed of equal amounts of concentrated nitric and sulfuric acid mixed with chromium trioxide dissolves the OPyC layer completely. The most favourable experimental conditions for removal of OPyC from a single coated fuel particle were identified and found to depend on the etching solution composition and etching temperature. Light microscopy yielded first-hand information on the surface features of the samples. It allowed fast comparison of etched and untreated sample features. The outer surface of particles prior to chemical etching of the outer pyrolytic carbon layer appeared black in colour with an even surface compared to the etched surfaces which appeared to have an uneven metallic grey, shiny texture. The scanning electron microscope (SEM) examination of the chemically treated outer carbon layer samples gave information on the microstructure and it demonstrated that the outer pyrolytic carbon layer could be readily removed using a solution of HNO3/H2SO4/CrO3, leaving the exposed SiC layer. Complete removal of the layer was confirmed by energy dispersive X-ray spectroscopic (EDS) analysis of the particle surface. For etching the second layer, the silicon carbide layer, microwave-assisted chemical etching was the only heating technique found to be useful. However, experimental results demonstrated that this method has limited ability to digest the sample completely. Also common chemical etchants were found to be ineffective for dissolving this layer. Only fluoride containing substances showed the potential to etch the layer. The results show that a mixture consisting of equal amounts of concentrated hydrofluoric and nitric acid under microwave heating at 200 ºC yielded partial removal of the coating and localized attack of the underlying coating layers. The SEM analyses at different intervals of etching showed: partial removal of the layer, attack of the underlying layers and, in some instances, that attack started at grain boundaries and progressed to the intra-granular features. The SEM results provide evidence that etching of the silicon carbide layer is strongly influenced by its microstructure. From these findings, it is concluded that etching of the silicon carbide under the investigated experimental conditions yields undesirable results and that it does not provide complete removal of the layer. This method has the potential to etch the layer to some extent but has limitations. CopyrightDissertation (MSc)--University of Pretoria, 2013.
Chemical Engineering
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Chen, Jian-you, and 陳建佑. "Fabrication of Large-area Periodic Arrays of Single-crystalline Silicon Nanorods by Chemical Wet Etching Processes." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/45706381201509235121.
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碩士國立中央大學
化學工程與材料工程研究所
97
In the present study, we have demonstrated that large-area, length-tunable arrays of vertically aligned Si nanorod arrays were successfully produced on (001)Si substrates by using the PS nanosphere lithography combined with the Au-assisted selective chemical etching process. The crystal structures, formation kinetics, surface wetting behaviors, and optical properties of the Si nanorods produced have been investigated. The SEM and TEM examinations revealed that the diameter of the Si nanorods produced was very uniform and observed to be approximately 126 nm, corresponding to that of RIE-reduced PS sphere mask used. Based on the analyses of the TEM image and the corresponding SAED pattern, it can be concluded that all the produced Si nanorods were single crystalline and the Si nanorods formed along the [001] direction. After a series of cross-sectional SEM examinations, the length variations of Si nanorods produced with etching time for various reaction temperatures were obtained. By measuring the formation rates of Si nanorods at different reaction temperatures, the activation energy for the linear formation of Si nanorods could be determined from an Arrhenius plot to be about 76.7 kJ/mole. The results of the water contact angle measurements indicated that the surfaces of HF-treated Si nanorod arrays exhibited strong hydrophobicity with water contact angle of 125°-150°. The hydrophobic behavior of the HF-treated Si nanorods was discussed in the context of the Cassie model. The UV-Vis analysis results indicated that Si substrate with Si nanorod arrays exhibited low reflection properties (﹤5％) over the visible light range (400-800 nm).
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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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Lo, Min-Hsin, and 羅閔馨. "Sapphire removal and patterned sapphire substrates fabrication on GaN light emitting diode utilizing wet chemical etching technology." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/15038180323087161699.
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碩士國立臺灣大學
光電工程學研究所
96
Recently, wide-bandgap semiconductors have been attracting great interest for applications to optoelectronic devices such as light-emitting diodes (LEDs), for last few years, InGaN/GaN-based blue light-emitting diodes (LEDs) have been successfully fabricated and following comes the epochal of white light LED. However, for future illumination applications, it is very important topic to further enhance the external quantum efficiency of LED. In this research, sapphire removal and patterned sapphire substrates (PSS) were fabricated utilizing wet chemical etching technology. A 3H2SO4：1H3PO4 volume mixture was used as the etchant to etch the sapphire substrates with 280 °C, and we obtain three different kinds of PSS LED. The experiment results indicate that 1.3 micron cylinder PSS LED has 49 % efficiency enhancement than conventional LED at 20 mA injection current. In order to fabricate vertical-electrode LED, unlike the common technology, laser lift-off, we tried the commutative etching method to do the sapphire removal experiments employing 5H2SO4：1H3PO4 and 2H2SO4：1H3PO4 as the etchant. The etching rate ratio (RSapphire / Ru-GaN) is achieved 15. We may fabricate vertical-electrode LED utilizing the commutative etching method to remove the sapphire substrates in the future.
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Tsai, Hung-Yao, and 蔡弘堯. "Fabrication of V-grooved and Textured Single-Crystalline Silicon by Wet Chemical Etching for Buried Contact Solar Cell Applications." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/vrxs7h.
Full textAbstract:
碩士國立虎尾科技大學
機械與機電工程研究所
100
In this work, v-grooved and textured single-crystalline silicon were demonstrated by the tetramethyl ammonium hydroxide/ isopropyl alcohol (TMAH/IPA) and the KOH/IPA mixed wet chemical solutions, respectively, for the buried contact solar cell applications. The silicon dioxide was used as the etching barrier of TMAH. The tuning conditions include TMAH solution concentrations and the treated temperatures. The results suggest that the etching rate increases with increasing TMAH concentration below 15%. However, the etching rate decreases with increasing TMAH concentrations above 15%. Moreover, the etching rate increase with increasing treated temperature of TMAH solutions. The uniformities of textured surfaces were achieved by decreasing etching rate of KOH/IPA solutions. The lower etching rate can be obtained by adding the IPA into KOH solution. Experimental results indicate that the v-groove with texturization provide excellent light trapping and can be used as a promising metal contact for applications in buried contact solar cells.
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Lin, Yao-hsing, and 林耀星. "Fabrication of Site- and Size-controllable Periodic Arrays 2D Well-ordered Si Nanostructures by Plasma Modified Nanosphere Lithography and Chemical Wet Etching Processes." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/23119866571253488366.
Full textAbstract:
碩士國立中央大學
化學工程與材料工程研究所
100
The present study has demonstrated the successful fabrication of density-, size- and shape-controllable Si nanostructure arrays on Si substrates of different orientation by using plasma modified nanosphere lithography and anisotropic wet etching process. The morphologies, crystal structures, compositions, optical and surface properties of the Si nanostructure arrays produced have been systematically investigated by SEM, AFM, TEM, SAED, EDS, XPS, UV-Vis and contact angle analyses. For the fabrication of periodic Si nanohole arrays, we take advantage of O2 plasma RIE treatment, which allows us simultaneously to adjust the diameter of PS nanospheres template and to form a passivation a-SiOx layer on Si serving as the etching mask. The shapes, sizes and positions of Si nanoholes that formed on Si substrates could be tuned by adjusting the diameters of the colloidal nanospheres and the KOH etching time. On the other hand, by combining the plasma modified nanosphere lithography, selective chemical etching process or metal silicide formation, large-area, size- and height-tunable Si nanocone arrays were also successfully fabricated on (001), (110) and (111)Si substrates in this study. From the water contact angle measurements, the surface of HF-treated Si nanohole and nanocone arrays exhibited hydrophobic characteristics. The hydrophobic behavior of Si nanostructures could be explained by the Cassie model. Furthermore, UV-Vis spectroscopic measurements revealed that the nanostructured Si surfaces exhibit strong antireflection properties.The enhanced antireflection properties can be attributed to the light trapping effect resulting from the nanostructure-arrayed Si surfaces.
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Katsaros, Georgios [Verfasser]. "Investigation of the properties of SiGe islands by selective wet chemical etching and scanning probe microscopy = Untersuchung der Eigenschaften von SiGe-Halbleiterinseln durch selektives nasschemisches Ätzen und Rastermikroskopie / vorgelegt von Georgios Katsaros." 2006. http://d-nb.info/980199514/34.
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Röper, Stephanie. "Strukturuntersuchungen an biologischen Materialien mit Hilfe rasterkraftmikroskopiebasierender Nanotomographie." Doctoral thesis, 2010. https://monarch.qucosa.de/id/qucosa%3A19527.
Full textAbstract:
Ziel ist die räumliche Abbildung biologischer Materialien (Knochen, Kollagenfibrillen und Zähne) hinsichtlich deren Struktur auf der Nanometerskala mit Hilfe der Nanotomographie. Die Nanotomographie ist eine moderne dreidimensionale Volumenabbildungsmethode auf der Nanometerskala basierend auf der Rasterkraftmikroskopie. Für die Nanotomographie wurden Ätzprotokolle an Zähnen, Kollagenfibrillen und Knochen entwickelt, die einen gleichmäßigen Abtrag bewirken. Lineare Verschiebungen der aufgenommenen Schichten werden mit Hilfe der manuellen Registrierung korrigiert und zu einem Volumenbild rekonstruiert. Ein zentrales Ergebnis sind dabei erste hochaufgelöste Volumenbilder einzelner Kollagenfibrillen im nativen Knochen. Neben der konventionellen Nanotomographie wird ein Ansatz zur automatisierten Nanotomographie mit einer Auflösung von 10 nm am Beispiel des menschlichen Knochens und Zahnes demonstriert. Mit Hilfe von mikroskopischen und elektronenmikroskopischen Techniken wurden die verschiedenen Strukturebenen des humanen Zahn und Knochens abgebildet und die räumlichen Strukturen der TM-AFM-Bilder auf der Mikro- und Nanometerskala eingeordnet. Darüber hinaus konnte mit Hilfe analytischer Messmethoden die chemische Zusammensetzung des kortikalen nativen Knochens erfasst werden und Änderungen durch das Ätzen detektiert werden.