Comments on the scattering of charged particles by single crystals. (1–3) IV. Quasichanneling, flux peaking and atom location

Abstract

Attention is drawn to barrier tip states which are set up when a collimated beam of charged particles enters a crystal. Such states, well known in quantum mechanical theories for the scattering of charged particles by crystals, are not contained in classical theories where immediate separation into channeled and random beams is assumed. For heavy particles barrier tip states describe ions which are neither channeled nor random. In Rutherford back scattering spectra with planar crystallographic alinement these quasichanneled ions give rise to a damped oscillatory yield with depth. Suggestions are made for the application of quasichanneling to studies of stopping powers and interatomic potentials, as well as to radiation damage, diffusion in alloys, thermal decomposition and in-depth stoichiometry investigations. A note of caution is sounded on the interpretation of conventional low resolution experiments involving lattice location of shallow implanted atoms by flux peaking, and of areas under damage or surface peaks. A contribution to sputtering yields from quasichanneled ions is pointed out.