Global ETD Search

11	Melting in Superheated Silicon Films Under Pulsed-Laser Irradiation Wang, Jin Jimmy January 2016 (has links) This thesis examines melting in superheated silicon ﬁlms in contact with SiO₂ under pulsed laser irradiation. An excimer-laser pulse was employed to induce heating of the ﬁlm by irradiating the ﬁlm through the transparent fused-quartz substrate such that most of the beam energy was deposited near the bottom Si-SiO₂ interface. Melting dynamics were probed via in situ transient reﬂectance measurements. The temperature proﬁle was estimated computationally by incorporating temperature- and phase-dependent physical parameters and the time-dependent intensity proﬁle of the incident excimer-laser beam obtained from the experiments. The results indicate that a signiﬁcant degree of superheating occurred in the subsurface region of the ﬁlm. Surface-initiated melting was observed in spite of the internal heating scheme, which resulted in the ﬁlm being substantially hotter at and near the bottom Si-SiO₂ interface. By considering that the surface melts at the equilibrium melting point, the solid-phase-only heat-ﬂow analysis estimates that the bottom Si-SiO₂ interface can be superheated by at least 220K during excimer-laser irradiation. It was found that at higher laser ﬂuences (i.e., at higher temperatures), melting can be triggered internally. At heating rates of 10¹⁰ K/s, melting was observed to initiate at or near the (100)-oriented Si-SiO₂ interface at temperatures estimated to be over 300K above the equilibrium melting point. Based on theoretical considerations, it was deduced that melting in the superheated solid initiated via a nucleation and growth process. Nucleation rates were estimated from the experimental data using Johnson-Mehl-Avrami-Kolmogorov (JMAK) analysis. Interpretation of the results using classical nucleation theory suggests that nucleation of the liquid phase occurred via the heterogeneous mechanism along the Si-SiO₂ interface. Excimer lasers Thin films Thin films--Effect of radiation on Thin films--Thermal properties Silicon oxide films Materials science Chemistry, Physical and theoretical
12	Photo And Thermal Induced Studies On Sb/As2S3 Multilayered And (As2S3)1-xSbx Thin Films Naik, Ramakanta 07 1900 (has links) (PDF) Chalcogenide glasses have attracted considerable attention due to their infrared transparency, low phonon energy, and high non linear optical properties. They have been explored as promising candidate for optical memories, gratings, switching devices etc. Because of their low phonon energy and high refractive indices, now a days these are used for high efficiency fibre amplifiers. Nevertheless, the availability of amorphous semiconductors in the form of high quality multilayers provides potential applications in the field of micro and optoelectronics. Among amorphous multilayers, chalcogenide multilayers are attractive because of the prominent photoinduced effects. Studies in chalcogenide amorphous multilayer have been directed towards two phenomena. One is photoinduced interdiffusion in short period multilayer systems which finds potential applications in holographic recording and fabrication of phase gratings . The other is photo darkening or photobleaching which is also known in thick films. These multilayers exhibit prominent photoinduced effects, similar to those exhibited by uniform thin films. In spite of its practical usefulness, the mechanism of photoinduced interdiffusion is not properly understood. Since most structural transformations are related to atomic diffusion, understanding of the structural transformation must be based on the diffusion process. The main aim of this thesis is to study the photoinduced diffusion in Sb/As2S3 multilayered films and (As2S3)1-xSbx thin films. In literature, there are reports about the photoinduced interdiffusion in Se/As2S3 and Bi/As2S3 multilayered films, but the mechanisms of photoinduced interdiffusion of these elements are not very clear. Raman scattering and infrared spectroscopy techniques have been used to study the photoinduced interdiffusion in Se/As2S3 and Bi/As2S3 multilayered films by Malyovanik et al. (M. Malyovanik, M. Shiplyak, V. Cheresnya, T. Remeta, S. Ivan, and A. Kikineshi, J. Optoelectron. Adv. Mater. 5, 397 (2003). But many questions remain unanswered. The characteristic spectra of components in the multilayer and those of the diffused layer were rather similar. In the present thesis, photoinduced interdiffusion in Sb/As2S3 multilayered samples are studied by Fourier Transform Infrared spectroscopy (FTIR) at room and low temperature and X-ray photoelectron spectroscopy (XPS). The photoinduced effects in (As2S3)1-xSbx thin films are studied by FTIR, XPS and Raman Spectroscopy. The detailed information about the distribution of electronic states in the absorption edge, localized states and the new bonds formed between the components due to photoinduced interdiffusion elucidated from the above studies will give more insight into the mechanism and kinetics of photoinduced interdiffusion. The thesis consists of seven chapters. References are given at the end of each chapter. Thin Films - Thermal Properties Thin Films - Photonic Properties Amorphous Chalcogenides Chalcogenide Glasses Sb/As2S3 Films (As2S3)1-xSbx Thin Films Se/As2S3 Films Nano-multilayered Film Nanomultilayered Film Solid State Physics
13	Nanolithography on thin films using heated atomic force microscope cantilevers Saxena, Shubham 01 November 2006 (has links) Nanotechnology is expected to play a major role in many technology areas including electronics, materials, and defense. One of the most popular tools for nanoscale surface analysis is the atomic force microscope (AFM). AFM can be used for surface manipulation along with surface imaging. The primary motivation for this research is to demonstrate AFM-based lithography on thin films using cantilevers with integrated heaters. These thermal cantilevers can control the temperature at the end of the tip, and hence they can be used for local in-situ thermal analysis. This research directly addresses applications like nanoscale electrical circuit fabrication/repair and thermal analysis of thin-films. In this study, an investigation was performed on two thin-film materials. One of them is co-polycarbonate, a variant of a polymer named polycarbonate, and the other is an energetic material called pentaerythritol tetranitrate (PETN). Experimental methods involved in the lithography process are discussed, and the results of lithographic experiments performed on co-polycarbonate and PETN are reported. Effects of dominant parameters during lithography experiments like time, temperature, and force are investigated. Results of simulation of the interface temperature between thermal cantilever tip and thin film surface, at the beginning of the lithography process, are also reported. Characterization Deflection Setpoint Grain rearrangement Array Precise positioning Metrology Explosion Explosives Data storage Material Image processing Slow scan disabled Temperature Tip Local In-situ Nanoscale Electrical circuit fabrication Repair Co-polycarbonate Polymers Polycarbonates Energetic materials PETN Simulation Interface Nano-manufacturing Experiment Calibration Raman Frequency Deflagration Decomposition Detonation Build up Pile-up End capped End capping Cross linked Cross-linked Conductivity Microscale MEMS Microcantilever NEMS DPN tDPN Silicon Glass Peak InVOLS Manipulation AFM Atomic force microscope Defense Nanoscale Surface Stiffness Force Scan size Thermal cantilevers Imaging Lithography Nanolithography Thin films Cantilevers Heaters Technology Nanotechnology Scan velocity Scan rate Bake Anneal Pentaerythritol tetranitrate Thin films Thermal properties Atomic force microscopy Microlithography Nanotechnology Surfaces (Technology) Analysis

Page generated in 0.1003 seconds