Michigan Technological University
Department of Physics

is pleased to announce the

Graduate Students Series Spring 2004

James D. Chye

Physics Graduate Student
Michigan Technological University
Advisor: Dr. David F. Nitz

Determining Primaries in the Highest Energy Cosmic Rays

The Auger Observatory is being built to detect the highest energy cosmic
rays. While reconstructing the arrival direction is relatively straight
forward and determining the total energy is fairly well understood, the
nature of the primary is more difficult to discern. Interpretation of the
data is required to separate different species of primary. I will discuss
techniques under refinement for the determination of the primaries through
analysis of single station digital signal traces. It will take several years
for the observatory to collect sufficient statistics for the final
determination and application. The techniques are being tested now through
simulation.

Haiying He

Physics Graduate Student
Michigan Technological University
Advisor: Dr. Ravindra Pandey

Molecular Modeling of Diffusion of Water
in Amorphous Silicon Carbide

Silicon Carbide (SiC) is a material of choice for devices operable under
extreme conditions, such as high temperature, high electric fields, high
frequency, and high power. In this respect, it has distinct advantages over
the traditional silicon-based counterparts. Amorphous SiC films can be
produced at low temperatures (T < 500 °C) with excellent properties like
extraordinary electronic properties, good mechanical resistance, high
hardness, very high thermal stability and chemical inertness. However, in a
large number of technological applications, water has been found to be the
main cause of oxidation and corrosion, leading to the degradation of
SiC-based devices and their properties. It is, therefore, extremely
important to evaluate the water permeability of SiC, specifically for thin
films of amorphous SiC.

In this work, we have studied the permeability of the water molecule in this
material using the molecular orbital theory and a cluster model for thin
films of amorphous SiC. In the cluster model, the local structure of
amorphous SiC is described by a model constructed from rings of the -Si-C-
elemental units. The calculated activation energy for diffusion of the
molecular water is found to vary with the chosen ring-size. In this model
of fully saturated network, the water molecule does not either break up or
attach to the SiC network along the diffusion path, and the energy barrier
for diffusion mainly depends on the local ring topology of the network.

Thursday, April 8, 2004

4:00 p.m., Fisher 139

Refreshments will be served

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