The effects of low-energy scattering on positron implantation

Abstract

Existing Monte‐Carlo models are capable of simulating the behavior of positrons incident at keV energies, then following the energy loss process to arbitrary final kinetic energies of from 20 eV to 100 eV. In the present work we describe a Monte‐Carlo simulation of the final stages of positron thermalization in Al, from 25 eV to thermal energies, via the mechanisms of conduction‐electron and longitudinal acoustic phonon scattering. We show that the later stages of thermalization can have important effects on the stopping profiles and mean depth. We describe a novel way to obtain information about positron energy loss by considering the time‐evolution of a point‐concentration (delta‐function distribution) of positrons. We examine, for the first time in the context of a positron Monte‐Carlo calculation, the effects of a positive positron work function. Finally, we discuss some issues relating to the agreement of Monte‐Carlo calculations with experimental data.