Advances in microlithography, dry etching, scaling of devices, ion-implantation, process control, and computer aid design brought the integrated circuit technology into the era of VLSI circuits. Those circuits are characterized by high packing density, improved performance, complex circuits, and large chip sizes. Interconnects and their spacing dominate the chip area of VLSI circuits and they degrade the circuit performance through the unacceptable high time delays. Multilayer metallization enables shorter interconnects, ease of design and yet higher packing density for VLSI circuits. It was shown in this dissertation that, tungsten films deposited in a cold-wall LPCVD reactor offer viable solution to the problems of VLSI multilayer interconnects. Experiments showed that LPCVD tungsten films have good uniformity, high purity, low resistivity, low stress-good adherence and are readily patterned into high resolution lines. Moreover, a multilayer interconnect system consisting of three layers of tungsten metallization followed by a fourth layer of aluminum metallization has been designed, fabricated and tested. The interlevel dielectric used to separate the metal layers was CVD phosphorus doped silicon dioxide. Low ohmic contacts were achieved for heavily doped silicon. Also, low resistance tungsten-tungsten intermetallic contacts were obtained. In addition to excellent step coverage, high electromigration resistance of interconnects was realized. Finally, CMOS devices and logic gates were successfully fabricated and tested using tungsten multilayer metallization schemes.

A pair of light beams that have orthogonal polarizations and equal intensity can be generated through reflection and refraction of a monochromatic light at a dielectric surface. Sytematic procedures to design beam splitters which can produce such output light beams are described in this thesis. Two designs that are of particular interest are prismatic substrates coated by a single layer and a double layer of thin films. Specific examples of each beam splitter in the visible and infrared are included. The performance of each beam splitter as a function of incidence angle, film thickness, and wavelength is also discussed.

No description available.

<div>Because of the limited reserve of fossil fuels and issues brought up by their combustion, the demand on renewable energy is considerably increasing. Solar energy is one of the most promising renewable energy sources considering the large amount of solar irradiation received by Earth and solar cell is such a device that allows us to directly convert sunlight directly into electricity. In this thesis, kesterite (I2-II-IV-IV4) system is the main focus as the light absorber material in thin film solar cells.</div><div><br></div><div>Cu2ZnSn(S,Se)4 (CZTSSe) has been first studied intensively. However, due to the band tailing resulting from Cu-Zn anti-site defects, further improvement on power conversion efficiency of this material has been hindered. Substituting Cu with Ag is expected to solve this problem by decreasing this defect density as a result of the high formation energy of Ag-Zn antisite defects. Herein, different concentrations of Ag are used to substitute Cu in the kesterite system through a nanoparticle-ink route for the fabrication of light absorber thin films. For Ag-alloying concentration less than 50%, it suggests that the Ag can induce inhomogeneity as well as secondary phase formation during nanoparticle formation. Moreover, Ag alloying is shown to enlarge the grain size and reduce film roughness after selenization, which are beneficial for the optoelectronic properties and device performance.</div><div><br></div><div>Additionally, the synthesis process for kesterite Ag2ZnSnS4 nanoparticles is explored. AZTS nanoparticles are achieved by solvent-thermal reaction. The reaction pathway during reaction is investigated by different material characterization methods to shed light on the Ag-based nanoparticle synthesis. The final nanoparticles obtained have high crystallinity and homogeneous composition, demonstrating great potential as light absorber materials. Also, the sulfide nanoparticles are converted into selenide thin films in Se vapor at elevated temperature (selenization). The selenization conditions, including temperature, heating ramp and selenization time, are optimized for the pure phase kesterite AZTSe thin films with large and dense grains. The optoelectronic properties are explored on these films and an initial research already demonstrates a 0.35% power conversion efficiency as the first solution processed AZTSe device.</div><div><br></div><div>In summary, multiple material characterization techniques are utilized to understand the microstructure evolution, phase transformation, and composition change for solution-processed nanoparticles and their resulting thin films. The material characteristics, process methods and film optoelectronic properties are associated for the future analysis and development of kesterite thin films for photovoltaic applications.</div><div><br></div>

Thesis advisor: Dunwei Wang / Non-aqueous Li-O2 batteries promise the highest theoretical specific energy among all rechargeable batteries. It is the only candidate that can be comparable with the internal combustion engine in terms of gravimetric energy density. This makes Li-O2 batteries preferable in the application of electric vehicles or drones. However, the materialization of this technology has been hindered by the poor cycling performance. The major reason for the degradation of the battery at the current research stage has been identified as the decomposition of the electrolyte and the cathode. These parasitic reactions will lower the yield of the desired product and induce huge overpotential during the recharge process. By carefully examining the degradation mechanism, we have identified the reactive oxygen species as the culprit that will corrode the cathode and attack the organic solvents. While parallel efforts have been devoted to reduce the reactivity of these species toward electrolyte, the main focus of this thesis is to identify suitable material platforms that can provide optimum performance and stability as cathodes. A bio-inspired wood-derived N-doped carbon is first introduced to demonstrate the benefit of hierarchical pore structures for Li-O2 cathodes. But the instability of the carbon cathode itself limits the lifetime of the battery. To improve the stability of carbon, we further introduce a catalytic active surface coating of FeOx on a three dimensionally ordered mesoporous carbon. The isolation of carbon from the reactive intermediates greatly improves the stability of the cathode. Yet the imperfections of the protection layer on carbon calls for a stable substrate that can replace carbon. TiSi2 is explored as the candidate. With the decoration of Pd catalysts, the Pd/TiSi2 cathode can provide extraordinary stability toward reactive oxygen species. But this composite cathode suffers from the detachment of the Pd catalyst. A Co3O4 surface layer is further introduced to enhance the adhesion of the catalyst, which doubles the lifetime of the cathode. To achieve a fully stable cathode, Ru catalyst with stronger adhesion on TiSi2 directly is explored and identified to be robust in the operating conditions of Li-O2 batteries. The expedition for stable cathodes in Li-O2 batteries is expected to provide a clean material platform. This platform can simplify the study in evaluating the effectiveness of catalysts, the reaction mechanism at the cathode and the stability of the electrolyte. Toward the end of this thesis, an exploration is made to enable rechargeable Mg metal battery with a conversion Br2 cathode. This new system can avoid the dendritic growth of Li metal by the adoption of Mg as the anode and can promise better cathode kinetics by forming a soluble discharge product. / Thesis (PhD) — Boston College, 2017. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis advisor: Krzysztof Kempa / Thesis advisor: Zhifeng Ren / In the past few decades, accompanied by the fascinating development of micro- and nano-fabrication techniques, the successful integration of subwavelength optics and multilayer structures has led to a number of remarkable discoveries. In this work, I present both experimental and theoretical investigations of the optics of thin metallic films with micro-/nano-scale perforations in the UV-VIS-IR ranges. Different fabrication techniques are employed, including nanosphere lithography, grain boundary lithography, crack templates, and sintered nanoparticles. The optical properties these films are studied, revealing important relation between optical response and the film geometry. This includes the evolution of plasmonic resonances in a series of periodic arrays of holes in a metallic film, with hole sizes increasing gradually until an array of islands is achieved. This evolution is an analog of the percolation problem, and critical phenomena are observed at the percolation threshold. Multilayer broad-band electromagnetic absorbers are also designed and fabricated based on the study of these perforated films. Parallel with these observations, an analytical coherence model is proposed to bridge the subwavelength and superwavelength limits. Such a model also provides an alternative way to handle thin random structures, avoiding large quantity of numerical computation. These studies can find applications in the design of sensors, ultrathin solar cells and transparent electrodes, as well as in applications where random structures are widely used. / Thesis (PhD) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

Este trabalho tem por objetivo a investigação de atenuação de ondas acústicas superficiais (OAS) em filmes finos granulares supercondutores de PbO e Pb depositados por sputtering reativo em substratos piezoelétricos de LiNbO3 e quartzo (ST). As medidas de atenuação de OAS em função da temperatura foram efetuadas para diferentes potências de radiofreqüência, e em freqüência variando de 550 MHz a aproximadamente 700 MHz. A atenuação de OAS medida em filme granular de chumbo (550&#197), dotada de alta resistividade de filme (de 1000 &#937/&#9001) se manifesta piezoeletricamente induzida e proporcional à resistividade do filme. No estado supercondutor esta medida de atenuação excede esta simples relação. Esta atenuação excedente é atribuída à resistência local produzida pela presença de dipolos de vórtice-antivórtice / The subject of this work is the investigation of surface acoustic waves (SAW) on superconducting Pb and PbO granular thin films deposited by sputtering on piezoelectric substrate (LiNbO3 and quartz ST). The SAW attenuation was measured as a function of the temperature (1,3K to 20K) for different r.f. Power, in frequencies from 550 MHz to 700 MHz. The SAW attenuation, measured on granular lead film (550 &#197) with high sheet resistivity (1000 &#937/&#9001) appears to be piezoelectrically induced and should be proportional to the sheet resistivity. In the superconducting state the measured attenuation exceeds this simple relation. This excess attenuation is ascribed to the local resistance produced by the presence of vortex-antivortex dipoles

by Tang Yeung Shun. / On t.p., "2", u "3", "7-x", and O"3" are subscripts following "growth of" in the title. / Parallel title in Chinese characters. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves 87-89). / Chapter Chapter 1 ： --- Introduction --- p.1 / Chapter Chapter 2 : --- Preparation of Thin Films --- p.10 / Chapter Chapter 3 : --- Structural Analysis / Chapter 3.1 --- Setup of XRD --- p.14 / Chapter 3.2 --- θ-2θ Scan --- p.17 / Chapter 3.3 --- Rocking Curve --- p.27 / Chapter 3.4 --- Pole Figure --- p.29 / Chapter 3.5 --- Off-axis Scan --- p.33 / Chapter 3.6 --- Grazing Incidence X-ray Diffraction --- p.53 / Chapter 3.7 --- Percentage of (110) Phase --- p.59 / Chapter 3.8 --- Lattice Parameters --- p.63 / Chapter Chapter 4 : --- Transport Properties / Chapter 4.1 --- Experimental --- p.66 / Chapter 4.2 --- Results --- p.68 / Chapter Chapter 5 : --- Surface Morphology --- p.75 / Chapter Chapter 6 : --- Discussion --- p.80 / Chapter Chapter 7 : --- Conclusions --- p.85 / References --- p.87 / Appendix A : Powder Diffraction Patterns of YBCO System

by Sou Ka Hou. / On t.p. "2', "3", and "T" are subscript following "deposition of" in the title. / Parallel title in Chinese characters. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1992. / Includes bibliographical references (leaves [88]). / Chapter 1. --- Introduction --- p.1 / Chapter 2. --- Computer-controlled sputtering system for deposition of high Tc thin films --- p.10 / Chapter 2.1 --- Introduction --- p.10 / Chapter 2.2 --- Vacuum system --- p.12 / Chapter 2.3 --- Gas flow control --- p.16 / Chapter 2.3.1 --- Design --- p.16 / Chapter 2.3.2 --- Flow control --- p.18 / Chapter 2.4 --- Gas pressure control --- p.21 / Chapter 2.4.1 --- Gauges --- p.21 / Chapter 2.4.2 --- Control method --- p.21 / Chapter 2.5 --- "Sputtering, guns and deposition control" --- p.24 / Chapter 2.5.1 --- Types --- p.24 / Chapter 2.5.2 --- Orientation of the sputter gun --- p.26 / Chapter 2.5.3 --- Dual magnetron gun system --- p.26 / Chapter 2.5.4 --- Deposition control system --- p.27 / Chapter 2.6 --- Substrate holder and temperature control --- p.30 / Chapter 2.6.1 --- Substrate holder --- p.30 / Chapter 2.6.2 --- Substrate temperature control --- p.31 / Chapter 2.7 --- Interlock protection --- p.34 / Chapter 2.8 --- Control program --- p.35 / Chapter 3. --- The presputtering effect --- p.39 / Chapter 3.1 --- Presputtering effect (a review) --- p.39 / Chapter 3.2 --- Emission spectroscopy on sputtered materials --- p.48 / Chapter 3.3 --- Experimental --- p.49 / Chapter 3.4 --- Emission spectra --- p.53 / Chapter 3.4.1 --- Effect of sputter power source --- p.53 / Chapter 3.4.2 --- Effect of gas ratio --- p.58 / Chapter 3.4.3 --- Effect of gas pressure --- p.64 / Chapter 3.4.4 --- Study of presputtering effect --- p.67 / Chapter 3.4.5 --- Monitoring the evaporation rate by the spectral line intensities --- p.71 / Chapter 4. --- Conclusion and discussion --- p.75 / Chapter Appendix A. --- Motor control --- p.77 / Chapter Appendix B. --- Thin film deposition --- p.82

by Poon Sai Keung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1978. / Includes bibliographical references (leaves 92-94).