Effect of surface roughness and morphology on sputtering yield
Abstract
The purpose of the present study is to investigate the impact of surface roughness on the sputtering yield of materials as a function of incident energy and angle. Material sputtering yield from ion bombardment is by far one of the most commonly studied topics. In most of the past research, bombarded surfaces are assumed to be flat and smooth in computer simulation or assumed to be exact self-similar fractals in analytical studies. However, both assumptions are not close enough to the true material surfaces. In this research, we developed an innovative way to describe the surfaces by combing the random fractal surface in computer graphics area with the ion bombardment simulation code: Ion Transport in Materials and Compounds (ITMC). With this new method, we can construct different levels of roughness on the surface and observe how the sputtering yield will change with incident ion angle and energy. Intensive literature review for both experimental and theoretical recent work is done and summarized in this study. Mathematical background information for fractal geometry, roughness exponent and fractal Brownian motion are carefully described and explained. The developed random fractal model has been tested against various experimental results and it is demonstrated that the model is suitable to describe the behavior of surface roughness. Surface roughness exponent of 0.53 for fractal surface with 5 keV argon ions incident on iron surface is simulated and compared to experimental data to optimize the mesh size in ITMC. Then, computer simulation of 5 keV argon bombarding graphite target and 1 keV argon ions bombarding silicon target are also compared to experimental data. All results are explained and discussed carefully for physical understanding and to avoid possible errors. Through this computer simulation approach, it is quite adequate to use the developed random fractal model to simulate the roughness behavior of material surfaces.
Degree
M.S.
Advisors
Hassanein, Purdue University.
Subject Area
Nuclear engineering|Materials science
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