Browsing by Subject "defect"
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Item Defect site prediction based upon statistical analysis of fault signatures(Texas A&M University, 2004-09-30) Trinka, Michael RobertGood failure analysis is the ability to determine the site of a circuit defect quickly and accurately. We propose a method for defect site prediction that is based on a site's probability of excitation, making no assumptions about the type of defect being analyzed. We do this by analyzing fault signatures and comparing them to the defect signature. We use this information to construct an ordered list of sites that are likely to be the site of the defect.Item Heteroepitaxial Self Assembling Noble Metal Nanoparticles in Monocrystalline Silicon(2013-08-13) Martin, Michael S.Embedding metal nanoparticles in crystalline silicon possesses numerous possible applications to fabricate optoelectronic switches, increase efficiency of radiation detectors, decrease the thickness of monocrystalline silicon solar panels and investigate fundamental properties. Noble metal nanoparticles made of gold or silver are grown in cavities in monocrystalline silicon formed by helium ion implantation and high temperature annealing at depth greater than 500 nm from the surface. Metals are introduced into the system by low energy ion implantation or physical vapor deposited thin film on the surface, and diffused into cavities by heat treatment. Nanoparticles nucleate on the inner surface of cavities heteroepitaxially and form face centered cubic crystal structure in the case of silver. Excessive heat treatment causes metal to be emitted from nanoparticles into bulk after trapping and nanoparticle formation. Helium ion implantation, annealing and diffusion heat treatment conditions have been optimized so that residual crystalline damage, point defects and dislocations, is reduced in monocrystalline silicon substrate.Item Influence of defects on thermal and mechanical properties of metals(2009-05-15) Kamani, Sandeep KumarThe crystallization/freezing and melting phenomena are critical in processing of chemicals and materials. Although melting is a very fundamental problem, the mechanism behind it has not been completely answered satisfactorily. Hence its study becomes very important. Perfect crystals do not exist; therefore it is very important to include the effect of defects in the above mentioned processes. The purpose of this work is to employ molecular simulation to further extend the understanding of theories of melting with respect to defects. We studied the melting and freezing process for a model system of copper with and without defects. We studied point defects (1, 2, 4, 8 vacancies and 1, 2, 4, 8 interstitials), line defects (edge dislocation) and surface defects (grain boundary) using molecular dynamics simulations. Constant stress-constant temperature ensemble with atmospheric pressures is employed. Various properties like average volume, density, potential energy and total energy are obtained as a function of temperature for each system. Most of the properties vary linearly before and after the phase transitions. During the transition process they show a dramatic change. This change is a sign of phase transition. The phase transition temperatures obtained from the single phase simulations are not the true melting (or freezing) points as there is some amount of superheating (or supercooling). Coexistence phase simulations are also done for the case of copper with no defects to find the true melting point. Most of the literature dealing with melting/crystallization on the basis of atomistic simulation does not include the influence of the presence of defects. Thus this work has a bearing on the various theories of melting.