Semi-conductor-to-metal transition and positron annihilation in V2O3

Abstract

Positron lifetime spectra in V2O3 have been recorded in the temperature range (80÷300) °K in which the transition to the metal state occurs. The occurrence of a complex positron time annihilation spectrum is ascribed to annihilations taking place in different positron band states. The positron lifetimesτ1=1.94·10−10s andτ2=4.74·10−10 s are found to be constant in the explored temperature range. This is explained in terms of localization of positron and electron wave functions. The observed behaviour with temperature of the intensities of the decay components is discussed as being due to the screening effect of the conduction electrons on the repulsive action of the V3+ lattice ions.