Theoretical studies of the positron mobility in diamond

Abstract

The positron mobility is calculated in diamond as a function of temperature taking into account acoustic phonon, optic phonon and impurity scattering processes. For acoustic phonon scattering the positron deformation potential has been calculated from volume derivatives of the electron and positron chemical potentials which were obtained using the pseudopotential technique and the frozen-core approximation respectively. The present calculations agree reasonably well with the experimental data in the high temperature region where the mobility is dominated by acoustic phonon scattering. At temperatures below 100 K we find that neutral impurity scattering can not explain the flat response of the data. Ionised impurity scattering while explaining the magnitude of the mobility cannot correctly explain the dependence of low temperature. The effect of positron shallow trapping on ionised impurities is discussed.