Gallium antimonide (GaSb) is a promising low-bandgap binary substrate for the fabrication of various infrared-based optoelectronic devices, particularly thermophotovoltaics (TPV). In order to make GaSb-based technologies like TPV more widely available, non-epitaxial dop- ing methods for GaSb must be pursued. Ion implantation is relatively unexplored for GaSb, and can offer advantages over the more common method of zinc diffusion, including higher flexibility with regards to substrate type and control over the resulting doping profile. Pre- vious work has shown beryllium (Be+) implantation to be a suitable method for fabricating a diode in an n-type GaSb substrate, opening the possibility for other ions to be considered for implanting into both n-type and p-type substrates. This work identifies sulfur (S+) as another species to investigate for this purpose. To do so, material and electrical characterization was done on S+ and beryllium implanted GaSb films grown onto a semi-insulating gallium arsenide (GaAs) substrate. X-ray Diffraction spectroscopy (XRD) and Atomic Force Microscopy (AFM) indicate that the post-implant anneal of 600 for 10 s repaired the implant damage in the bulk material, but left behind a damaged surface layer composed of coalesced vacancies. While the beryllium implant resulted in moderate doping concentrations corresponding to an activation percentage near 15 %, Hall Effect data showed that implanting S+ ions induced a strongly p-type behavior, with hole concentrations above 1 × 19 cm^3 and sheet hole densities 3.5 times higher than the total implanted dose. This strong p-type behavior is attributed to the remaining lattice damage caused by the implant, which induces a large density of acceptor-like defect states near the valence band edge. This technique was used on an unintentionally-doped p-type GaSb substrate to create a + /p junction. The implant process succeeded in producing a potential barrier similar to that of a hole-majority camel diode with a thin delta-doped region suitable for collecting diffused carriers from the p-type substrate. A post-fabrication etching process had the effect of strongly increasing the short circuit current density to as high as 41.8 mA/cm^2 and the open circuit voltage as high as 0.21 V by simultaneously removing a high carrier recombination surface layer. This etching process resulted in a broadband spectral response, giving internal quantum efficiencies greater than 90 %. / Doctor of Philosophy / Thermophotovoltaics (TPV) is a technology that converts light and other forms of electromagnetic energy into electrical power, much like a typical solar panel. However, instead of sunlight, the energy source used in a TPV system is a terrestrial heat source at a temperature range of 1250–1750 ◦C, whose radiation is primarily infrared (IR). The IR-absorbing qualities and commercial availability of the compound semiconductor gallium antimonide (GaSb) have made it a key component in the development of absorber devices for TPV-related systems. GaSb-based devices have most often been fabricated using epitaxy, a method in which layer(s) of material are ‘grown’ in a layer-by-layer fashion atop a substrate GaSb wafer to induce an interface between negatively-charged (n-type) and positively-charged (p-type) regions. In order to improve upon the scalability of TPV production, device fabrication methods for GaSb that avoid the use of epitaxy are sought after as a lower-cost alternative. In this work, sulfur ion implantation is examined as one of these methods, in which elemental sulfur ions are injected at a high energy into a p-type GaSb substrate. The implanted ions then alter the charge characteristics at the surface of the material, producing an electric field from which a photovoltaic (PV) device can be fabricated. The results of this study showed that by implanting sulfur ions, an extremely p-type (p++) layer was formed at the surface of the GaSb substrate, which was attributed to residual damage induced by the implant process. The resulting interface between the p++ surface and the moderately p-type GaSb substrate was found to induce an electric field suitable for a PV device. Removing the excess surface damage away from the device’s metal contacts resulted in an improvement in the output electrical currents, with measured values being significantly higher than that of other devices made using more common non-epitaxial fabrication methods. The success of this work demonstrates the advantages of using a p-type GaSb substrate in place of an n-type substrate, and could help diversify the types of TPV-related devices that can be produced.

Malgré son grand potentiel, l’énergie photovoltaïque n’arrive pas encore à trouver une grande place dans le paysage énergétique mondial. Elle se heurte à deux problèmes de taille : le coût et le rendement. Les cellules solaires à base du silicium multicristallin (mc-Si) perdent beaucoup de leur rendement à cause de la présence des impuretés métalliques. Plusieurs recherches ont montré que les cavités induites par implantation ionique sont efficaces dans le piégeage des impuretés. Mais les techniques utilisées dans l’implantation n’ont pas permis à ce procédé de se développer dans l’industrie à cause de leur coût élevé. Le plasma immersion ion implantation (PIII) est une technique bas coût qui permet d’implanter de grandes surfaces. Elle est utilisée dans le traitement de surface à l’échelle industrielle, mais à ce jour aucune étude n’a montré son utilisation dans le piégeage des impuretés dans le silicium. Dans cette thèse nous avons créé des cavités dans le mc-Si par implantation d’hydrogène par PIII. Plusieurs techniques de caractérisation ont été utilisées afin d’étudier le mécanisme de formation de ces cavités. La MET, la photoluminescence et les positons ont été utilisées pour avoir un maximum d’informations sur la nature et l’évolution des défauts créés par implantation d’hydrogène. Nous avons également étudié la différence entre les cavités formées par PIII et celles formées par implantation classique. Les cavités formées ont été utilisées, par la suite, pour le piégeage des impuretés métalliques présentes dans le mc-Si (Cu, Fe, Cr et Ni). Les résultats obtenus par SIMS ont monté l’efficacité de notre procédé dans le piégeage des impuretés métalliques. / Extraction of silicon metal impurities to be used for photovoltaic by plasma immersion ion implantation (PII)

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22442号 / 工博第4703号 / 新制||工||1734(附属図書館) / 京都大学大学院工学研究科原子核工学専攻 / (主査)教授 斉藤 学, 教授 神野 郁夫, 准教授 松尾 二郎 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The aim of this work is to analytically treat the dynamic ion behavior during the evolution of the ion matrix sheath, considering the industrial application plasma source ion implantation for both planar and cylindrical targets, and then to de-velop a code that simulates this dynamic ion behavior numerically. If the sepa-ration between the electrodes in a discharge tube is small, upon the application of a large potential between the electrodes, an ion matrix sheath is formed, which fills the whole inter-electrode space. After a short time, the ion matrix sheath starts moving towards the cathode and disappears there. Two regions are formed as the matrix sheath evolves. The potential profiles of these two regions are derived and the ion flux on the cathode is estimated. Then, by us-ing the finite-differences method, the problem is simulated numerically. It has been seen that the results of both analytical calculations and numerical simula-tions are in a good agreement.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

No description available.

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.

The sub-surface region of chemical vapour deposition (CVD) diamond was transformed by C+ ion implantation followed by isochronal annealing up to 1200 oC. Different implantation regimes and with different energies at different implantation temperatures would give different thicknesses were studied. This enabled a study in the evolution of the stiffness of the damaged layer as a function of annealing. The technique of choice for this study was the non-destructive Brillouin light scattering (BLS) utilizing two scattering geometries; indirectly scattered phonons (Kr¨uger-type geometry) for temperature anneals up to 600 oC, and the conventional surface ripple mechanism up to 1200 oC. It has been argued that surface acoustic waves (SAW) on a transparent medium are enhanced by applying a thin metallic reflective layer on the surface, this study has showed that opacity of the substrate is key. In fact, bulk modes with SAW-like characteristics emanating from indirect photon scattering off phonons after reflection at the smooth reflective back of the sample dominated down to transmission below 5% which was observed after annealing between 500-600 oC (low annealing temperatures). The other complementing techniques employed to understand the changing structure of the ion implanted diamond were Raman spectroscopy, electromagnetic transmission in the visible range, electron energy loss spectroscopy (EELS) and high-resolution transmission electron microscopy (HRTEM) in addition to theoretical techniques: transport of ions in matter (TRIM), finite element modelling (FEM) and elastodynamic Green’s functions. Although the electronic techniques showed a structurally changing material at the low annealing temperatures, the optical ones did not show significant changes in the ion-damaged material possibly due to lack of distinct interface between the pristine diamond and the ion irradiated region at these lower annealing temperatures.

by Ranganathan Venugopal. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (p. 150-165). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Hui Yat Wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves 106-108). / Acknowledgments / Abstract / Chapter 1. --- Introduction --- p.1 / Chapter 2. --- Theory / Chapter 2.1 --- Optical Waveguide --- p.4 / Chapter 2.1.1 --- Optical Waveguide Classification / Chapter 2.1.2 --- Theoretical Analysis of 2-dimensional Step Index Waveguides / Chapter 2.2 --- Optical Waveguides Measurement --- p.18 / Chapter 2.2.1 --- Refractive Index Measurement / Chapter 2.2.2 --- Loss Measurement / Chapter 2.3 --- Ion Implantation and Annealing --- p.36 / Chapter 2.4 --- Refractive Index Change --- p.40 / Chapter 3. --- Equipments and Their Experimental Setup / Chapter 3.1 --- Light Source-Laser Diode --- p.42 / Chapter 3.2 --- Ellipsometry Measurement System --- p.45 / Chapter 3.2.1 --- Ellipsometry Measurement System and its Existing Problems / Chapter 3.2.2 --- Improvement of the Original System / Chapter 3.2.3 --- System Calibration / Chapter 3.3 --- Reflectance Measurement System --- p.51 / Chapter 3.3.1 --- System Design and Setup / Chapter 3.3.2 --- System Calibration / Chapter 3.4 --- End-Coupling Measurement System --- p.56 / Chapter 3.4.1 --- System Setup / Chapter 3.4.2 --- System Calibration / Chapter 4. --- Experiment / Chapter 4.1 --- Samples Preparation --- p.77 / Chapter 4.2 --- Refractive Index Measurement by Ellipsometer --- p.80 / Chapter 4.3 --- Refractive Index Measurement by Reflectance --- p.84 / Chapter 4.4 --- Waveguide Measurement --- p.88 / Chapter 4.4.1 --- Fiber-Waveguide Coupling / Chapter 4.4.2 --- Lens-Waveguide Coupling / Chapter 5. --- Results and Discussion / Chapter 5.1 --- Refractive Index Change and Waveguide Formation --- p.94 / Chapter 5.2 --- Mechanism of Refractive Index Change --- p.100 / Chapter 6. --- Conclusion --- p.103 / Chapter 7. --- Improvement and Extension --- p.105 / Reference --- p.106 / Appendices / Chapter A. --- Thick.m --- p.VI / Chapter B. --- Distrib.m --- p.IX