Production of Nanowires on Semiconductor Surfaces by Ion Bombardment

Abstract

Low energy (typically in the keV regime) ion bombardment of some semiconductor materials can lead to the development of regularly spaced ripples on the surfaces, which with suitable doping procedures, can be employed as nanowires. Although these ripples are reminiscent of those induced by the action of wind on sand dunes or by water currents on the seabed, the mechanisms are different. The formation of the bombardment-induced ripples depends primarily on the material sub-strate. The average distance between the ripples, i.e. ripple wavelength is also a function of ion spe-cies, ion energy, angle of incidence, ion areic dose and substrate temperature. In this paper, some of the reported results on the effect of areic dose on ripples produced by noble gas, oxygen and nitrogen ion bombardment on selected semiconductor materials will be tested against Bradley-Harper theory. Some of the ripple properties can be explained by this analytic theory. The analysis suggests that room temperature bombardment of silicon might be transition regime between those of a low ion areic dose rate at high temperature and a high areic dose rate at low temperature bombardment. For a full understanding of bombardment-induced topography on semiconductor surfaces at room temperature, one will have to resort to the more advances theories, which can only be solved numerically, with all it associated difficulties.