Literatura académica sobre el tema "Breakdown (Electricity)"

<p>An experimental evaluation of the breakdown characteristics of the nonunifonn electric fields established between two spheres and between two points in a crossflow was conducted and the results were then compared to the breakdown characteristics in quiescent air. The aluminum spheres used in this investigation ranged in diameter from 0.635 em to 2.54 em. The points had a radius of curvature of 0.5 mm. The velocities of the crossflow ranged from 23 mls to 58 mls and the gap distances ranged from 0.5 cm to 2.0 cm. Photography was used to determine the effect of the crossflow on the luminous spark for all electrodes. The sparking voltages in the crossflow were a function of the crossflow velocity, electrode size and gap distance. It was concluded that the most significant increase of sparking voltages in a crossflow, as compared to the same configuration in quiescent air, was for the point-point gap at a distance of 2.0 cm for a 58 mls crossflow. As the electrodes were increased in size, the effect of a given crossflow decreased. For the 2.54 cm spheres with a 58 mls crossflow, there was actually a decrease in the sparking voltage as compared to its counterpart in quiescent air. The photographs showed a significant deflection of the spark in the direction of the crossflow for the point-point gap, but no significant deflection was detected for the other electrode geometries.<br>Master of Science

In this work, we have investigated numerical techniques to determine the breakdown behavior of complex semiconductor devices using two-dimensional simulation. In particular, we have augmented the device simulator SEPSIP with a capability for handling single and multiple floating field rings, and for handling devices with slanted edges. We have furthermore improved the grid width selection algorithm in SEPSIP. A capability for plotting equi-field contours was added to the code. Finally, all system dependencies were removed from the SEPSIP code, and a new version of SEPSIP (Version 2.0) was generated which can be executed on any PC/XT, PC/AT, or PC/386 compatible computer. This eliminates the need for transfering files back and forth between the PC, which had formerly been used as an I/O processor, and the VAX, which was used for numerically intensive computations. It also makes the code more accessible to scientists and engineers who are working in this important research area.

This thesis describes an experimental investigation and analysis of two topical problems in condensed matter physics: 1.) the effect of a magnetic field on quantum states of an electron bound to a shallow donor impurity in a quantum well heterostructure and 2.) the breakdown of the quasi-dissipationless state of the integer quantum Hall effect. Two introductory chapters describe important material parameters and the experimental equipment and techniques used. Magneto-tunneling spectroscopy (MTS) is used to probe the spatial form of the eigenfunction of electrons bound in the ground state of a shallow Si-donor impurities in a GaAs/(A1Ga)As quantum well. An in-plane magnetic field, B[subscript] |, acts to tune the k-vector of the tunnelling electron through the effect of the Lorentz force. The variation with B [subscript] | of the tunnel current through the donor ground state provides a map of the Fourier transform, |ψ(k)| [superscript]2, of the probability density of the ground state donor wavefunction in real space. By applying a strong magnetic field component, B [subscript] ||, parallel to the direction of tunnel current, it is possible to magneto-compress the donor function in real space. The magneto-compression is investigated using MTS and the data are analysed in terms of a simple model, which is critically discussed. The breakdown of the integer quantum Hall effect is investigated by measuring the variation of the voltage drop Vxx along the direction of current flow for a range of currents and magnetic fields and for a number of sample geometries including Hall bars with narrow channels. The data are discussed in terms of two complementary models of breakdown: the bootstrap electron heating model and magneto-exciton formation at a charged impurity. Evidence is found for both types of breakdown depending on the type of sample used and on experimental parameters. For samples with constrictions, it is found that in the breakdown region the value of Vxx measured across a pair of contacts on one side of the Hall bar can differ substantially from that measured on the other side. A model based on magneto-exciton formation at impurities is proposed to explain this unexpected effect. The thesis concludes with a brief summary and suggestions for future work.

This dissertation summarizes the research performed towards the development, analysis, and testing of two new sample configurations used for characterizing dielectric materials over a wide band of frequencies. In the two configurations, a cylindrical cavity completely filled with a sample of the dielectric material of interest is used. The two configurations are the following: 1. The cylindrical cavity is adapted to the end of a transmission line and the reflection coefficient is measured. The complex permittivity of the dielectric sample is then derived from the measured reflection coefficient information. 2. The cylindrical cavity is placed between two transmission lines. The complex permittivity of the dielectric material can be computed from either the measured reflection coefficient or the measured transmission coefficient. The full field analysis of these configurations is carried out and the solution is obtained using the method of moments. Computer simulation experiments are performed to test the sensitivity of these techniques and predict their performance. Actual experiments on some dielectric materials with known dielectric properties are performed for verification. The first configuration is also used to characterize two thick film dielectric materials. These configurations proved to provide solutions to the many problems with the conventional configurations found in the literature.<br>Ph. D.

The impact of physical design characteristics on backend dielectric reliability was modeled. The impact of different interconnect geometries on backend low-k time dependent dielectric breakdown was reported and modeled. Physical design parameters that are crucial to backend dielectric reliability were identified. A methodology was proposed for determining chip reliability but combining the insights gathered by modeling the impact of physical design on backend dielectric breakdown. A methodology to model variation in device parameters and characteristics was proposed. New methods of electrical and physical parameter extraction were proposed. Models that consider systematic and random source of variation in electrical and physical parameters of CMOS devices were proposed, to aid in circuit design and timing analysis.

Transport Properties of Wide Band Gap Semiconductors Louis Tirino III 155 pages Directed by Dr. Kevin F. Brennan The objective of this research has been the study of the transport properties and breakdown characteristics of wide band gap semiconductor materials and their implications on device performance. Though the wide band gap semiconductors have great potential for a host of device applications, many gaps remain in the collective understanding about their properties, frustrating the evaluation of devices made from these materials. The model chosen for this study is based on semiclassical transport theory as described by the Boltzmann Transport Equation. The calculations are performed using an ensemble Monte Carlo simulation method. The simulator includes realistic, numerical energy band structures derived from an empirical pseudo-potential method. The carrier-phonon scattering rates and impact ionization transition rates are numerically evaluated from the electronic band structure. Several materials systems are discussed and compared. The temperature-dependent, high-field transport properties of electrons in gallium arsenide, zincblende gallium nitride, and cubic-phase silicon carbide are compared. Since hole transport is important in certain devices, the simulator is designed to simulate electrons and holes simultaneously. The bipolar simulator is demonstrated in the study of the multiplication region of gallium nitride avalanche photodiodes.