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Tesis sobre el tema "Crystals Apatite. Silicon crystals"

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Publicado: 4 de junio de 2021
Última modificación: 9 de febrero de 2022

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1

Rulis, Paul Michael Ching Wai-Yim. "Computational studies of bioceramic crystals & related materials". Diss., UMK access, 2005.

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Thesis (Ph. D.)--Dept. of Physics and School of Computing and Engineering. University of Missouri--Kansas City, 2005.
"A dissertation in physics and computer networking." Advisor: Wai-Yim Ching. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed March 12, 2007. Includes bibliographical references (leaves 256-267). Online version of the print edition.
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2

Balmforth, Barnaby William. "Silicon photonic crystals for quantum optics applications". Thesis, University of Cambridge, 2009. https://www.repository.cam.ac.uk/handle/1810/252125.

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3

Deng, Xin y 鄧欣. "Positron studies of silicon and germanium nanocrystals embedded in silicon dioxide". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B41508749.

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4

Deng, Xin. "Positron studies of silicon and germanium nanocrystals embedded in silicon dioxide". Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B41508749.

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5

Van, Hoose Ashley Elizabeth. "Apatite Crystal Populations of the 1991 Mount Pinatubo Eruption, Philippines: Implications for the Generation of High Sulfur Apatite in Silicic Melts". PDXScholar, 2012. https://pdxscholar.library.pdx.edu/open_access_etds/123.

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On June 15, 1991, Mount Pinatubo, Philippines, ejected 20 million tonnes of sulfur dioxide into the atmosphere, significantly impacting global climate and stratospheric ozone. Recharging basaltic magma mixed into the 50 km³ dacitic magma reservoir 6 to 11 km beneath Mount Pinatubo, and triggered the 1991 eruption. The result of the magma mixing was a hybrid andesite with quenched basalt inclusions that erupted as a dome between June 7 and June 12. On June 15, approximately 5 km³ of anhydrite-bearing magma was erupted from the main phenocryst-rich, dacitic reservoir. This study will utilize this extraordinary framework of the 1991 Pinatubo eruption to investigate the systematics of sulfur uptake by apatite in order to further develop apatite as a monitor for magmatic sulfur. In the dacite and hybrid andesite, apatite occurs as individual phenocrysts (up to ~200 μm diameter) or included within anhydrite, hornblende, and plagioclase phenocrysts. In the basaltic magmatic inclusions, apatite is found as acicular microphenocrysts. Electron microprobe data collected on apatite yield low- (0.7 wt.% SO₃) apatites in all juvenile products, and show that two distinct populations of apatites exist: "silicic" apatites (hosted in dacite and andesite) and basalt apatites. Apatites crystallizing from silicic melt have predominantly low- to medium-sulfur contents, but high-sulfur apatites with as much as 1.2-1.7 wt.% SO₃ occur sporadically as inclusions in plagioclase, hornblende, Fe-Ti oxide, and anhydrite. These concentrations are much higher than what could be achieved through equilibrium crystal-melt partitioning at pre-eruption conditions (760±20°C, 220MPa, NNO+1.7, 77 ppm S in melt inclusions) and a partition coefficient of 13. Apatite in the basalt is always sulfur-rich with compositions forming a continuous array between 0.7 to 2.6 wt.% SO₃. The population of apatite that crystallized from silicic melt has elevated cerium, fluorine, and chlorine and lower magnesium concentrations (average dacite values in wt.%: 0.21 Ce₂O₃, 1.4 F, 1.1 Cl, & 0.14 MgO) relative to the population of apatite from the basalt (average basalt values in wt.%: 0.05 Ce₂O₃, 1.0 F, 0.78 Cl, & 0.22 MgO). LA-ICP-MS trace element data also show distinct apatite populations between silicic and basalt apatites. Silicic apatites have elevated REE concentrations (La avg. = 750 ppm), lower Sr (avg.= 594 ppm), and a pronounced negative Eu anomaly (avg. Eu/Eu* = 0.57) relative to basalt apatites (avg. values: 217 ppm La, 975 ppm Sr, and Eu/Eu* = 1.16). The correlation of EMP sulfur data and LA-ICP-MS trace element data show no difference between high-S and low-S silicic apatites. These compositional systematics rule out the possibility that sulfur-rich apatite from dacite are inherited from mafic magma. Sulfur element maps of apatites show no evidence of S-diffusion from anhydrite hosts. Areas of high-S concentrations show complicated patterns that suggest multiple periods of sulfur enrichment. High-S silicic apatites are likely the product of "fluid-enhanced crystallization" from early enrichment of a SO₂ rich fluid phase from the underplating basalt, which occurred prior to or at anhydrite saturation. This fluid phase is the only possible sufficient source of sulfur for generating high-S apatites in a cool, "wet", dacitic melt. The dynamics of apatite sulfur enrichment via "fluid-enhanced crystallization" is yet unclear and requires further experimental laboratory investigation.
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6

Rao, Yeswanth Lakshman. "A process for hydrogenation of silicon carbide crystals". Master's thesis, Mississippi State : Mississippi State University, 2001. http://library.msstate.edu/etd/show.asp?etd=etd-04102001-131544.

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7

Schonbrun, Ethan. "Negative refraction and anomalous propagation in silicon photonic crystals". Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3256376.

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8

Lee, Grace W. (Grace Wang). "Optical absorption of bismuth silicon oxide (Bi₁₂SiO₂₀) crystals". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/114089.

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Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2001.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 23).
The purpose of this work is to characterize the optical absorption in bismuth silicon oxide (Bi₁₂SiO₂₀) crystals grown using the Bridgman technique and to identify electronic transitions responsible for absorption. Optical measurements were taken in the range of 0.4 - 11 pm at 300 K and 77 K using a spectrometer. The results show that near the band edge, there is evidence of indirect transitions at 2.3 eV and excition transitions at 1.8 eV. Low temperature measurements revealed peaks of free carrier absorption in the visible light range at 1.7 eV and 2.1 eV. Illuminated samples at low temperature revealed empty donor levels in the visible range at 1.6-1.9 eV and 2.1 eV, indicating the presence of the photochromic effect and photorefractivity.
by Grace W. Lee.
S.B.
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9

Brody, Jed. "Doping dependence of surface and bulk passivation of multicrystalline silicon solar cells". Diss., Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04082004-180041/unrestricted/brody%5Fjed%5F200312%5Fphd.pdf.

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10

Naseh, Sasan. "Experimental investigation of anisotropic etching of silicon in tetra-methyl ammonium hydroxide". Thesis, Connect to online version, 1995. http://0-wwwlib.umi.com.mercury.concordia.ca/cr/concordia/fullcit?pMQ90888.

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11

Ghosh, Kunal. "Modeling of amorphous silicon/crystalline silicon heterojunction by commercial simulator". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 48 p, 2009. http://proquest.umi.com/pqdweb?did=1654493871&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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12

Jamois, Cécile. "Silicon-based planar photonic crystals for application to dispersion compensation". [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972527796.

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13

Hobbs, Neil Townsend. "Anisotropic etching for silicon micromachining". Thesis, Virginia Tech, 1994. http://hdl.handle.net/10919/40632.

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Silicon micromachining is the collective name for several processes by which three dimensional structures may be constructed from or on silicon wafers. One of these processes is anisotropic etching, which utilizes etchants such as KOH and ethylene diamine pyrocatechol (EDP) to fabricate structures from the wafer bulk. This project is a study of the use of KOH to anisotropically etch (lOO)-oriented silicon wafers. The thesis provides a thorough review of the theory and principles of anisotropic etching as applied to (100) wafers, followed by a few examples which serve to illustrate the theory. Next, the thesis describes the development and experimental verification of a standardized procedure by which anisotropic etching may be reliably performed in a typical research laboratory environment. After the development of this procedure, several more etching experiments were performed to compare the effects of various modifications of the etching process. Multi-step etching processes were demonstrated, as well as simultaneous doublesided etching using two different masks. The advantages and limitations of both methods are addressed in this thesis. A comparison of experiments performed at different etchant temperatures indicates that high temperatures (800 C) produces reasonably good results at a very high etch rate, while lower temperatures (500 C) are more suited to high-precision structures since they produce smoother, higher-quality surfaces.
Master of Science

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14

McDonald, Andrew Michael Carleton University Dissertation Geology. "The crystal structures of three minerals: phosinaite-(Ce), abenakiite-(Ce) and yoshimuraite, with remarks on the crystal chemistry of silicophosphates". Ottawa, 1992.

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15

Işık, Nebile Güneş Mehmet. "The effects of deposition conditions on the low energy absorption spectrum of microcrystalline silicon thin films prepared by HWCVD method/". [s.l.]: [s.n.], 2005. http://library.iyte.edu.tr/tezler/master/fizik/T000340.pdf.

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Thesis (Master)--İzmir Institute Of Technology, İzmir, 2005.
Keywords: Microcrystalline silicon, absorption, spectroscopy, defect, dual beam photoconductivity. Includes bibliographical references (leaves. 81-86).
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16

Morton, Jonathan Andrew Scott. "2D photonic crystals to enhance up-conversion emission for silicon photovoltaics". Thesis, Heriot-Watt University, 2016. http://hdl.handle.net/10399/3110.

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This thesis investigates the application of 2D photonic crystals to enhance the emission of up-conversion layers to improve the efficiency of silicon photovoltaics. Two up-conversion material compositions are of particular interest in this work: erbium doped titanium dioxide (TiO2:Er) and erbium doped yttrium fluoride (YF3:Er). The 2D photonic crystals under investigation are composed of TiO2:Er and air; and YF3:Er and silicon. These nano-structures are investigated using both simulation and experimental methods. Further work in this thesis analyses the properties of the highly conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) for use as a transparent electrode and thin film electrically conductive adhesive for the application of silicon photovoltaics. The design and geometrical parameters for the 2D photonic crystals were optimised through simulations (plane wave expansion and finite-difference time-domain), before the structures were experimentally fabricated and optically characterised. The novel analysis of the refractive index of the prepared up-conversion materials using ellipsometry was a key step in the design of the photonic crystal structures. A maximum photoluminescence enhancement of 3.79 times was observed for the 980 nm emission profile, however this could not be successfully attributed to a photonic crystal effect. The optical, mechanical and electronic properties of PEDOT:PSS were characterised for thin film samples, using novel ellipsometry analysis.
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17

Shankar, Raji. "Mid-Infrared Photonics in Silicon". Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10988.

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The mid-infrared wavelength region (2-20 µm) is of great utility for a number of applications, including chemical bond spectroscopy, trace gas sensing, and medical diagnostics. Despite this wealth of applications, the on-chip mid-IR photonics platform needed to access them is relatively undeveloped. Silicon is an attractive material of choice for the mid-IR, as it exhibits low loss through much of the mid-IR. Using silicon allows us to take advantage of well-developed fabrication techniques and CMOS compatibility, making the realization of on-chip integrated mid-IR devices more realistic. The mid-IR wavelengths also afford the opportunity to exploit Si's high third-order optical nonlinearity for nonlinear frequency generation applications. In this work, we present a Si-based platform for mid-IR photonics, with a special focus on micro-resonators for strong on-chip light confinement in the 4-5 μm range. Additionally, we develop experimental optical characterization techniques to overcome the inherent difficulties of working in this wavelength regime. First, we demonstrate the design, fabrication, and characterization of photonic crystal cavities in a silicon membrane platform, operational at 4.4 μm (Chapter 2). By transferring the technique known as resonant scattering to the mid-IR, we measure quality (Q) factors of up to 13,600 in these photonic crystal cavities. We also develop a technique known as scanning resonant scattering microscopy to image our cavity modes and optimize alignment to our devices. Next, we demonstrate the electro-optic tuning of these mid-IR Si photonic crystal cavities using gated graphene (Chapter 3). We demonstrate a tuning of about 4 nm, and demonstrate the principle of on-chip mid-IR modulation using these devices. We then investigate the phenomenon of optical bistability seen in our photonic crystal cavities (Chapter 4). We discover that our bistability is thermal in origin and use post-processing techniques to mitigate bistability and increase Q-factors. We then demonstrate the design, fabrication, and characterization grating-coupled ring resonators in a silicon-on-sapphire (SOS) platform at 4.4 μm, achieving intrinsic Q-factors as high as 278,000 in these devices (Chapter 5). Finally, we provide a quantitative analysis of the potential of our SOS devices for nonlinear frequency generation and describe ongoing experiments in this regard (Chapter 6).
Engineering and Applied Sciences
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18

Ramanachalam, M. Swaminathan. "Correlation of defects and electrical properties in Si and ZnO". Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/19675.

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19

Armstrong, Jeffrey Lee. "Reaction of carbonyl-and nitrogen-containing molecules on Si(100) and fluxless solder re-flow on polycrystalline Cu surfaces /". Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.

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20

Yeldandi, Satish. "Development of fabrication processes for Si and GaN photonic crystal structures". Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5915.

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Thesis (M.S.)--West Virginia University, 2008.
Title from document title page. Document formatted into pages; contains xi, 99 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 80-83).
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21

Tang, Xiaoli Dong Jianjun. "Theoretical study of thermal properties and thermal conductivities of crystals". Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SUMMER/Physics/Dissertation/Tang_Xiaoli_9.pdf.

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22

Chen, Yang. "A universal species ion implantation model for implants into topographically complex structures with multiple materials". Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3025007.

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23

Rey, Isabella H. "Active slow light in silicon photonic crystals : tunable delay and Raman gain". Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/3356.

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In the past decade, great research effort was inspired by the need to realise active optical functionalities in silicon, in order to develop the full potential of silicon as a photonic platform. In this thesis we explore the possibility of achieving tunable delay and optical gain in silicon, taking advantage of the unique dispersion capabilities of photonic crystals. To achieve tunable optical delay, we adopt a wavelength conversion and group velocity dispersion approach in a miniaturised engineered slow light photonic crystal waveguide. Our scheme is equivalent to a two-step indirect photonic transition, involving an alteration of both the frequency and momentum of an optical pulse, where the former is modified by the adiabatic tuning possibilities enabled by slow light. We apply this concept in a demonstration of continuous tunability of the delay of pulses, and exploit the ultrafast nature of the tuning process to demonstrate manipulation of a single pulse in a train of two pulses. In order to address the propagation loss intrinsic to slow light structures, with a prospect for improving the performance of the tunable delay device, we also investigate the nonlinear effect of stimulated Raman scattering as a means of introducing optical gain in silicon. We study the influence of slowdown factors and pump-induced losses on the evolution of a signal beam along the waveguide, as well as the role of linear propagation loss and mode profile changes typical of realistic photonic crystal structures. We then describe the work conducted for the experimental demonstration of such effect and its enhancement due to slow light. Finally, as the Raman nonlinearity may become useful also in photonic crystal nanocavities, which confine light in very small volumes, we discuss the design and realisation of structures which satisfy the basic requirements on the resonant modes needed for improving Raman scattering.
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24

Avella, Paola. "Characterisation of silicon photomultipliers coupled to inorganic scintillating crystals for timing applications". Thesis, University of Surrey, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.580335.

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Silicon Photo multipliers (SiPM) are solid-state photo detectors made of a matrix of Avalanche Photodiodes working in Geiger mode (GM-APD). Each APD behaves as a binary device, giving in output a standardised signal if fired by one or more photons. However, the device as a whole is an analog device, giving in output a pulse proportional to the number of incident photons. For this reason, the SiPM can be considered as a solid-state equivalent of the traditional Photomultiplier Tube (PMT), with the advantage of single photon counting capability, improved detection efficiency at wavelengths that better suit scintillating crystals' output and of compactness, ruggedness as well as easier production technology. Moreover, being a solid state device, the SiPM is also insensitive to magnetic fields and characterised by an intrinsic timing resolution which makes it a good candidate for fast timing applications. The motivation behind this thesis is the study of a system made of inorganic scintillating crystals readout by various types of SiPMs with specific interest in timing applications. The characterisation of various SiPMs with different total area and pixel sizes is discussed. The main result of this analysis is the measurement of the parameters of these photo detectors that allows the simulation of their output pulses, which ultimately determine the single photon response and hence the intrinsic performance limit of the device. In particular, it was found that coherent light improves the timing performances of SiP Ms, due to an improvement in signal to noise ratio, while almost maintaining the single photon response. For this reason, the Intrinsic and Coincidence Time Resolution (ITR and CTR respectively), i.e. the variance on the time the detector takes to respond to a light stimulus and the uncertainty introduced in the measurement of the time coincidence, were measured using a femtosecond laser. For both quantities, values ofthe order of tens of ps were found optimising the parameters of a low pass Butterworth filter and of a time stamp pick-up algorithm which is the digital equivalent of a Constant Fraction Discriminator, for two Hamamatsu MPPCs with different total area and same pixel size. Finally the characterisation of various size LYSO crystals readout by SiPMs is also reported. This study gives information on the timing and energy properties of a Gamma sensitive system and allows the understanding of the characteristics that the optimum scintillating crystal readout by SiPMs should have to optimise the coincidence time and energy resolution. Values of the CTR for a system made of two LYSO crystals with size 3 x 3 x 10 mm ' readout by a pair of MPPCs with 25 uu: pixel size and 3 x 3 mm'' total area, were found of the order of 300 ps. Hence, this detector system appears as a good candidate for timing applications involving the detection of coincident gamma rays, particularly in applications like the Time-of- Flight Positron Emission Tomography, where an excellent timing resolution imply very good spatial resolution and hence superior quality of the final image.
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25

Giannattasio, Armando. "Interaction of oxygen and nitrogen impurities with dislocations in silicon single-crystals". Thesis, University of Oxford, 2004. http://ora.ox.ac.uk/objects/uuid:41cf8568-8411-4a85-8788-7d390307c7c3.

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An experimental technique based on the immobilisation of dislocations by segregation of impurity atoms to the dislocation core (dislocation locking) has been developed and used to investigate the critical conditions for slip occurrence in Czochralski-grown and nitrogen-doped floating-zone-grown silicon crystals. The accumulation of nitrogen and oxygen impurities along a dislocation and the resulting dislocation locking effect has been investigated in silicon samples subjected to different annealing conditions. In particular, the stress needed to unlock the dislocations after their decoration by impurities has been measured as a function of annealing duration and temperature. The approach used in this study has allowed the determination of new diffusivity data for oxygen and nitrogen in silicon in the technologically important range of temperatures 350-850°C. No other data covering such wide temperature range are available in the literature. In addition to transport properties, the binding energy of an impurity atom to a dislocation in silicon has been deduced from the experimental data in the case of oxygen and nitrogen impurities. A discussion in terms of the impurity species responsible for transport (monomers or dimers) and dislocation locking is also presented. The role of oxide precipitates in the generation of glide dislocation loops and the parameters affecting the occurrence of slip have been investigated in silicon samples containing precipitates of different sizes and different morphologies. The fundamental parameters deduced in this work have been used to develop a numerical model to investigate the effect of different heat treatments on the mechanical properties of silicon wafers containing a controlled distribution of impurities. This model has then been used to simulate real wafer processing conditions during device fabrication to show how they may be modified to increase dislocation locking. It is hoped that these results will have relevance to how wafers are processed in order to minimise or eliminate dislocation multiplication and consequent warpage.
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26

Li, Yang Yang. "Porous silicon photonic crystals as hosts for polymers, biopolymers, and magnetic nanoparticles /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3153688.

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27

Ahmad, S. A. "Theoretical studies of the structures of defects in silicon germanium and other crystals". Thesis, University of Surrey, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354752.

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28

CHINCHOLI, ASHWIN. "PARALLEL FABRICATION OF PHOTONIC CRYSTALS USING INTERFERENCE LITHOGRAPHY". University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1115996014.

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29

Kim, Sangcheol. "Fabrication of active and passive terahertz structures". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 60 p, 2006. http://proquest.umi.com/pqdweb?did=1203570961&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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30

Olivier, Ezra Jacobus. "Analysis of the extended defects in 3C-SiC". Thesis, Nelson Mandela Metropolitan University, 2008. http://hdl.handle.net/10948/730.

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The dissertation focuses on the analysis of the extended defects present in as-grown and proton bombarded β-SiC (annealed and unannealed) grown by chemical vapour deposition (CVD) on (001) Si. The proton irradiation was done to a dose of 2.8 × 1016 protons/cm2 and the annealing took place at 1300°C and 1600°C for 1hr. The main techniques used for the analysis were transmission electron microscopy (TEM) and high resolution TEM (HRTEM). From the diffraction study of the material the phase of the SiC was confirmed to be the cubic beta phase with the zinc-blende structure. The main defects found in the β- SiC were stacking faults (SFs) with their associated partial dislocations and microtwins. The SFs were uniformly distributed throughout the foil. The SFs were identified as having a fault vector of the type 1/3 <111> with bonding partial dislocations of the type 1/6 <121> by using image simulation. The SFs were also found to be predominantly extrinsic in nature by using HRTEM analysis of SFs viewed edge-on. Also both bright and dar-field images of SFs on inclined planes exhibited symmetrical and complementary fringe contrast images. This is a result of the anomalous absorption ratio of SiC lying between that of Si and diamond. The analysis of the annealed and unannealed irradiated β-SiC yielded no evidence of radiation damage or change in the crystal structure of the β-SiC. This confirmed that β-SiC is a radiation resistant material. The critical proton dose for the creation of small dislocation loops seems to be higher than for other compound semiconductors with the zinc-blende structure.
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31

Walker, Zane Harry. "Kinetics of the reaction of intrinsic and N-type silicon with atomic and molecular bromine and chlorine". Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/32378.

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The etching of silicon by atomic and molecular chlorine and bromine was studied as a function of etchant pressure and reaction temperature. Various types of silicon were employed in the etching experiments including intrinsic and n-type polycrystalline silicon as well as the (100) face of intrinsic single crystal silicon. The pressures of Cl₂ and Br₂ varied from 0.1 to 30 Torr and the partial pressure of Cl and Br atoms was between 0.08 and 0.2 Torr. Temperatures of between 365 and 600°C were required for CI₂ and Br₂ etching, while lower temperatures of 25 to 470°C were sufficient for the more reactive Cl and Br atoms. The reaction between silicon and Br atoms was shown to be first order with respect to the partial pressure of atoms and a first order dependence was assumed for Cl atom etching. The rate constants were determined for the Cl and Br atom etching of intrinsic and n-type polycrystalline silicon, with a dopant concentration of 5x10¹⁸ atoms cm⁻³. The reactivity of Cl atoms with n-type silicon was approximately 90 times greater than with intrinsic silicon. This enhancement in reaction rate is primarily due to an increase in the preexponential factor in k₁, with the activation enthalpy for the process remaining unchanged at approximately 28 kJ mol⁻¹. For Br atom etching, the reaction rate for the n-type silicon was over 300 times greater than for intrinsic silicon and was characterized by activation enthalpies of 55 and 63 kJ mol⁻¹ respectively. The enhancement in reactivity can also be attributed principally to an increase in the preexponential factor. The preexponential factors for the rate constants are larger than those expected, based on the collision frequencies of Cl and Br atoms. This is interpreted as evidence for a preadsorption step in these reactions. The reactions of silicon with CI₂ and Br₂ were found to display a complex pressure dependence. The etch rates varied linearly with (etchant pressure)¹′² and the intercepts from a linear regression of the data were slightly negative. To account for the half order pressure dependencies observed in these etching reactions, a reversible dissociative adsorption mechanism is proposed whereby Br₂ (or CI₂) is dissociatively adsorbed, in a reversible reaction, onto the silicon surface yielding two atoms bound to the surface. This step is then followed by a first order reaction leading to the formation of a species which is either gaseous product or some precursor which forms that product in a subsequent non rate-determining step. From the slopes of etch rate versus (pressure)¹′² plots, composite half order rate constants were calculated and from the intercepts it was possible to evaluate the rate constant for dissociative adsorption of the halogen molecules. At high etchant pressures, where the reaction was half order with respect to Br₂ (or CI₂), a half order "composite" rate constant characterized the etching reaction. Values for the half order rate constant were determined for a number of wafers at various temperatures. From the temperature dependencies of these rate constants, activation enthalpies of 131±8 and 116±7 kJ mol⁻¹ were calculated for Br₂ and CI₂ etching of intrinsic polycrystalline silicon respectively. A value of 121±7 kJ mol⁻¹ was deterrnined for the Br₂ etching of silicon (100). Higher reaction rates were observed for the etching of n-type polycrystalline silicon, with greater enhancements observed for Br₂ relative to Cl₂ etching. The enhancements in etch rates were found to be principally due to a lower activation enthalpy for the half order rate constant. An activation enthalpy for the composite rate constant of 82±3 kJ mol⁻¹ was determined for Cl₂ etching of n-type silicon with a dopant atom concentration of 5x10¹⁸ atoms cm⁻³. Br₂ etching of the same wafer yielded an activation enthalpy of 86±3 kJ mol⁻¹. At low pressures, the reaction becomes first order and the temperature dependence of the corresponding first order rate constant yielded activation enthalpies of 109 and 83 kJ mol⁻¹ for intrinsic and n-type polycrystalline silicon.
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32

Boreland, Matt. "Laser crystallisation of silicon for photovoltaic applications using copper vapour lasers". [Sydney : University of New South Wales], 1999. http://www.library.unsw.edu.au/~thesis/adt-NUN/public/adt-NUN1999.0055/index.html.

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33

Evertson, Scott Richard. "Experimental considerations of higher order parametric x-rays from silicon crystals of varying thicknesses". Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23667.

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Generation of parametric X-radiation (PXR) may be described as the Bragg scattering of virtual photons to 2dsin0(B), where 0(B) is the angle between the electronic beam and the crystal plane. Enhanced higher order parametric x-radiation from the <220> and <111> planes of silicon crystals of varying thicknesses were observed. Production of PXR of the order of N=1, and n=2 of the <200> n=1,n=3 and n=4 of the <111> planes of a 44 um and 320 um crystal were observed. Exploiting the formation and attenuation lengths of silicon crystals of various thicknesses, higher order x-radiation production is enhanced relative to the lower energy first order x-ray. Photons of 4.5 to 21 keV have been observed.
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34

Hutt, James. "The origin of equiaxed crystals and the grain size transition in aluminium-silicon alloys /". St. Lucia, Qld, 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16244.pdf.

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35

Khung, Yit Lung y y. khung@unsw edu au. "Porous Silicon Structures for Biomaterial and Photonic Applications". Flinders University. School of Chemistry, Physics and Earth Sciences, 2009. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20090421.145533.

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The primary research aim in this thesis is to demonstrate the versatility of porous silicon based nanomaterials for biomaterial and photonic applications. In chapter 2 of this thesis, the suitability of porous silicon as a biomaterial was investigated by performing different surface modifications on the porous silicon films and evaluating biocompatibility of these surfaces in vitro. The porous silicon surfaces were characteriszed by means of atomic force microscopy (AFM), scanning electron microscopy (SEM), diffuse reflectance infrared spectroscopy (DRIFT) and interferometric reflectance spectroscopy (IRS). Cell attachment and growth was studied using fluorescence microscopy and cell viability assays. Both fabrication of the porous silicon films and subsequent surface modifications were demonstrated. Polyethylene glycol functionalised porous silicon prevented cell attachment, whilst collagen or fetal bovine serum coating encouraged cell attachment. Surface modifications were also performed on porous silicon films with different pore sizes and the influence of pore size and surface modification on primary hepatocyte growth was recorded over a course of 2 weeks by means of laser scanning confocal microscopy (LSCM), toxicity and metabolic assays. On collagen-coated surfaces with average pore sizes of 30 nm, multilayer cells stacks were formed. This stacking behaviour was not observed on samples with smaller pore sizes (10 nm), or in the absence of collagen. Hepatocytes remained viable and functional (judging by a metabolic assay) for 6 days, after which they generally underwent apoptosis. Collagen-coated porous silicon films showed later onset of apoptosis than porous silicon films not coated with collagen or collagen-coated flat silicon.. In chapter 3 of this thesis, the nitrogen laser of a laser desorption/ionization (LDI) mass spectrometer was used to selectively ablate regions on porous silicon films that had been functionalised with a non-fouling polyethylene oxide layer, affording a microscale patterning of the surface. Surface characterization was performed by means of AFM, SEM, LDI mass spectrometry, DRIFT and IRS. This approach allowed the confinement of mammalian cell attachment exclusively on the laser-ablated regions. By using the more intense and focussed laser of a microdissection microscope, trenches in a porous silicon film were produced of up to 50 micron depth, which allowed the construction of cell multilayers within these trenches, mimicking the organization of liver cords in vivo. Fluorescent staining and LSCM was used to study cell multilayer organization. To gain a better understanding of how surface topography influences cell attachment and behaviour, porous silicon films were fabricated containing a gradient of pore sizes by means of asymmetric anodisation (chapter 4). These gradients allowed the investigation of the effect of subtle changes of pore size on cell behaviour on a single sample. Analysis by means of LSCM and SEM showed that pore size can dictate cell size and area as well as cell density. In addition, a region of pore size where cell attachment and proliferation was strongly discouraged was also identified. This information can prove to be useful for designing non-biofouling surface topographies. Using the same asymmetric anodisation setup, photonic mirrors gradients were produced and overlaid over one another to produce multidirectional lateral photonic mirror gradients that display a series of roving spectral features (photonic stop-bands) from each gradient layer (chapter 4). These multidirectional photonic gradients have the potential to serve as optical barcodes or contributing to the development of graded refractive index devices such as lenses for high quality image relay and graded-index optical fibers.
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36

Zhang, Zichen. "Phase-only nematic liquid crystal on silicon devices". Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610052.

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37

Blood, Arabella M. "A study of the electrical properties of defects in silicon". Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298320.

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38

Murphy, Robert Clayton. "Effects of material inhomogeneity on the terminal characteristics of polycrystalline silicon solar cells /". Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.

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39

Ho, King-fung y 何競豐. "Some positron annihilation studies on highly doped and supersaturated N-type silicon". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B30287108.

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40

Hardy, Julie. "Novel materials based on functionalised silsesquioxanes". n.p, 2000. http://library7.open.ac.uk/abstracts/page.php?thesisid=43.

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41

Wu, Hao. "Fundamental investigations of cutting of silicon for photovoltaic applications". Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45855.

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Crystalline silicon (Si) wafers used as substrates in the semiconductor and photovoltaic (PV) industries are traditionally manufactured using a multi-wire slurry sawing (MWSS) technique. Due to its high productivity potential, the fixed abrasive diamond wire sawing (DWS) technique is of considerable interest to Si wafer producers. Although both sawing techniques are currently used in the industry, a fundamental understanding of the underlying process is still lacking, particularly for diamond wire sawing. Consequently, optimization of the wire sawing process is carried out largely based on experience and trial and error. This thesis aims to develop a systematic fundamental understanding of diamond wire sawing of Si materials used for PV applications. First of all, a comparative analysis of the characteristics of silicon wafers cut by slurry and fixed abrasive diamond wire sawing is presented. The analysis results indicate that fixed abrasive diamond wire sawing may be a viable alternative to slurry wire sawing. Modeling and experimental studies of single grit diamond scribing of Si are proposed to shed light on the basic cutting mechanisms. Although Si is brittle at room temperature, it is possible to properly control the cutting conditions to obtain a completely ductile mode of material removal. The effects of material anisotropy, abrasive grit shape, friction condition and external hydrostatic pressure on the ductile-to-brittle mode transition in cutting of single crystal Si (sc-Si) are systematically investigated. Multicrystalline Si (mc-Si) based solar cells take up the majority of the global PV market. Hard inclusions (Silicon carbide and Silicon nitride) in multicrystalline Si (mc-Si) ingots may cause wire breakage and negatively impact the process, surface/subsurface morphology and mechanical properties of the resulting wafer. Their effects are experimentally studied through the single grit diamond scribing on the mc-Si sample with high density of inclusions. Finally, it is identified that there is a correlation between the high dislocation density and the increase of fracture toughness in mc-Si. The increase in fracture toughness leads to greater capability of ductile mode of cutting and higher specific scribing energy in the brittle fracture regime. Results of these fundamental investigations are expected to generate useful knowledge for optimizing the diamond wire sawing process in order to achieve high productivity and minimum surface/subsurface damage.
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42

Venezia, Vincent C. "Evolution of Vacancy Supersaturations in MeV Si Implanted Silicon". Thesis, University of North Texas, 1999. https://digital.library.unt.edu/ark:/67531/metadc277663/.

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High-energy Si implantation into silicon creates a net defect distribution that is characterized by an excess of interstitials near the projected range and a simultaneous excess of vacancies closer to the surface. This defect distribution is due to the spatial separation between the distributions of interstitials and vacancies created by the forward momentum transferred from the implanted ion to the lattice atom. This dissertation investigates the evolution of the near-surface vacancy excess in MeV Si-implanted silicon both during implantation and post-implant annealing. Although previous investigations have identified a vacancy excess in MeV-implanted silicon, the investigations presented in this dissertation are unique in that they are designed to correlate the free-vacancy supersaturation with the vacancies in clusters. Free-vacancy (and interstitial) supersaturations were measured with Sb (B) dopant diffusion markers. Vacancies in clusters were profiled by Au labeling; a new technique based on the observation that Au atoms trap in the presence of open-volume defects. The experiments described in this dissertation are also unique in that they were designed to isolate the deep interstitial excess from interacting with the much shallower vacancy excess during post-implant thermal processing.
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43

Sanchis, Kilders Pablo. "Coupling techniques between dielectric waveguides and planar photonic crystals". Doctoral thesis, Universitat Politècnica de València, 2008. http://hdl.handle.net/10251/1854.

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El objetivo de esta tesis es la investigación de estructuras y técnicas de acoplo para minimizar las pérdidas de acoplo entre guías dieléctricas y cristales fotónicos planares. En primer lugar se ha estudiado el modelado del acoplo entre guías dieléctricas y guías en cristal fotónico así como la influencia de los principales parámetros del cristal en la eficiencia de acoplo. Se han obtenido expresiones cerradas para las matrices de reflexión y transmisión que caracterizan totalmente el scattering que ocurre en el interfaz formado entre una guía dieléctrica y una guía en cristal fotónico. A continuación y con el fin de mejorar la eficiencia de acoplo desde guías dieléctrica de anchura arbitraria, se ha propuesto como contribución original una técnica de acoplo basada en la introducción de defectos puntuales en el interior de una estructura de acoplo tipo cuña realizada en el cristal fotónico. Diferentes soluciones, incluida los algoritmos genéticos, han sido propuestas con el objetivo de conseguir el diseño óptimo de la configuración de defectos. Una vez conseguido un acoplo eficiente desde guías dieléctricas a guías en cristal fotónico, se ha investigado el acoplo en guías de cavidades acopladas. Como contribución original se ha propuesto una técnica de acoplo basada en la variación gradual del radio de los defectos situados entre cavidades adyacentes. Además, se ha realizado un riguroso análisis en el dominio del tiempo y la frecuencia de la propagación de pulsos en guías acopladas de longitud finita. Dicho estudio ha tenido como objetivo la caracterización de la influencia de la eficiencia del acoplo en los parámetros del pulso. Finalmente, se han presentado los procesos de fabricación y resultados experimentales de las estructuras de acoplo propuestas.
Sanchis Kilders, P. (2005). Coupling techniques between dielectric waveguides and planar photonic crystals [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/1854
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44

Morris, Christopher J. "Capillary-force driven self-assembly of silicon microstructures /". Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/5963.

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45

Garcia, Victoria. "Effect of dislocation density on residual stress in polycrystalline silicon wafers". Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22621.

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46

Yurdanur, Tasel Elif. "Elemental Analysis Of Materials Including Silicon (100) And (111) Crystals With Single And Double Pulsed Libs". Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12614304/index.pdf.

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Laser Induced Breakdown Spectroscopy (LIBS) which is used to determine the elemental content of various samples, inspects the emission spectroscopy of samples of interest for searching certain elements or identifying the unknown content. In this study, spectroscopic analyses of various kinds of metals, namely, Cu, Fe, Mo, Ti, W, some compounds such as CuBe, ZnSe, ZnS, GaSe, some semimetals like Si, Ge and even gases were investigated by means of a compact-commercial portable LIBS system and an independently constructed experimental set-up consisting of a single pulse system and various kinds of double pulse configurations using Nd:YAG lasers. The contributions of this thesis to the LIBS community can be classified into two main groups- which are experimental and code development. One of the experimental contributions was the investigation of the different crystal surfaces of silicon in which dangling bond density were taken into account for a more precise comparison of atomic emissions. The second experimental contribution was the polarization experiments by which polarization dependency, to some extent, was demonstrated. The third and final one was the orthogonal double pulse configuration with a 45 o incidence angle for both lasers in opposite directions by which it was shown that the positioning becomes straightforward yielding the desired reproducible results. The second major contribution was to develop a basic code for analyzing the experimental data more accurately. In conclusion, by means of the different experimental approaches, factors relating to the enhancement in intensity were investigated and as a result of developing the code, flexibility in upgrading the constraints of element searching was obtained and the updating of the database was accomplished.
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47

Lin, Keh-moh. "Computer aided floating zone growth of germanium silicon crystals in a resistance heated multi-zone furnace". [S.l. : s.n.], 2002. http://www.freidok.uni-freiburg.de/volltexte/603.

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48

Hashimura, Akinori. "Single-crystal silicon HARPSS capacitive beam resonators". Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/15798.

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49

Wang, Licai. "Crystalline silicon thin film growth by ECR plasma CVD for solar cells". Thesis, London South Bank University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297927.

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50

Andrews, Gordon Todd. "Elastic and structural properties of supported porous silicon layers". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0004/NQ42470.pdf.

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