Modeling of Particle-Surface Reflections Including Surface Roughness Characterized by Fractal Geometry

J. Nucl. Mater., 162-164, 904-909 (1989).

Ruzic, D. N., Chiu, H. K.

The interactions of ions and neutral atoms with surfaces are important for all edge plasma calculations. However, current models treat surfaces as virtually flat two-dimensional objects. To solve this problem in a realistic manner, surface roughness has been added into the TRIM and Embedded Atom Method (EAM) computer codes through the use of fractals. A fractal is a geometric construct with noninteger dimension. Real surfaces have fractal dimensions between 2 and 3 which can be determined experimentally by using the BET gas adsorption method. Inclusion of surface roughness is particularly important at energies below 100 eV and at grazing angles of incidence. Results show that at grazing incidence the particle number and energy reflection coefficients are reduced by a factor of approximately two when even small amounts of surface roughness are included in the models.