Sub-Monolayer Ablation of II-VI Semiconductor Surfaces

Abstract

The pulsed laser ablation of compound semiconductors using above-bandgap radiation has been the subject of numerous experimental [1-4] and theoretical investigations [5]. Significant progress has been made in understanding the phenomenology of the ablation process, but many questions remain about the nature of the elementary ablation mechanism. It has recently been shown [5,6] that measurements of the velocity and angular distributions of particles ejected from the surface of a compound semiconductor during laser irradiation can be used to infer the energetics and dynamics of particle desorption, and thus provide useful information about the ablation mechanism. However, the interpretation of those experiments can be seriously complicated by the influence of near-surface collisions and changes in the surface structure and composition on the characteristics of the ejected particles. For example, multiple gas phase collisions have lead to inconsistencies between theoretical predictions [5] and experimental results [2] which show that the ejected products are characterized by translational temperatures that depend strongly on the angle and mass of the desorbed species. Likewise, the effect of surface damage on the behavior of the ejected particles may be manifested by non-stoichiometric and unstable yields, complex angular distributions, and flux characteristics arising from bulk diffusion processes.