A discussion on ion implantation and hyperfine interactions - The range and energy loss of implanted ions

Abstract

Since the early experiments of Rutherford at the beginning of the century there have been many measurements of the rate of energy loss, and, in recent years, the distribution profile of ions implanted into more or less amorphous media. The theoretical aspects of atomic penetration were established long ago by Bethe and Bohr, and have been extended over the past decade by Lindhard and his collaborators. Despite this progress, there are still important features concerning the mechanism of the energy loss of charged particles in matter which are poorly understood. There are two contributions to the energy loss, due to nuclear collisions and electronic collisions, and Lindhard has just discussed the degree to which these may be regarded as separable. The first type of collision dominates at low energies and is responsible for most of the angular dispersion of the ions. By developing a unified range theory in which a simple velocity-proportional Thomas─Fermi formula is used for the electronic stopping and a power-law dependence is assumed for nuclear stopping, Lindhard, Scharff & Schiøtt (1963) have provided universal formulae for ion ranges and range straggling. Some sensitive experiments by Jespersgård & Davies (1967) on range distributions of 24 Na, 42 K, 85 Kr and 133 Xe in amorphous Al 2 O 3 show good agreement with these formulae for energies up to about 100 keV. At higher energies the observed ranges were consistently somewhat higher, by as much as 30% at 1 MeV.