Vacancies selectively induced and specifically detected on the two sublattices of the intermetallic compoundMoSi2

Abstract

In the present study vacancies were selectively induced on the Si or predominantly on the Mo sublattices of ${\mathrm{MoSi}}_{2}$ single crystals by low-temperature irradiation with electrons of low or high energies. These vacancies were specifically detected by employing two-detector Doppler broadening measurements of the positron-electron annihilation \ensuremath{\gamma} quanta in addition to positron lifetime studies. Positron lifetime studies show that two kinds of vacancies on either the Si or the Mo sublattices were induced in ${\mathrm{MoSi}}_{2}$ by 0.5- or 3-MeV electron irradiation. After 0.5-MeV electron irradiation Doppler broadening spectra characteristic for Mo are detected, which shows that the vacancies with the 139 ps positron lifetime are located on the Si sublattice. After 3-MeV electron irradiation, only Si atoms were detected to surround the vacancy with the 156 ps positron lifetime, which demonstrates that in this case positrons are predominantly trapped by vacancies on the Mo sublattice. In the present experiment the selective introduction of vacancies and the detection of their location on different sublattices have proven to be a promising technique for specifically studying atomic defects in solids with a complex structure.