Characterization of Pb xMn 1− xS thin films prepared by flash evaporation technique

Abstract

Electron diffraction investigations carried out on flash evaporated lead manganese sulphide films with lead concentration x varied in the range 0.16 ≤ x ≤ 0.84, grown on freshly cleaved single crystal KCl substrates maintained at temperature T s of 65, 130, 165, 225 °C, indicate that these films have epitaxial growth with 〈100〉 zone axis orientation of the grains in all films and with a single phase fcc structure. The single phase fcc lattice indicates the presence of ternary materials of the type Pb x Mn 1− x S in the films. The structural characteristics of the films are explained by the atom-by-atom condensation process. Optical absorption studies reveal the presence of a single absorption edge indicating the presence of a single material phase and corroborate the presence of Pb x Mn 1− x S alloys in the films. The direct optical band gap of the film materials varies between 2.26 eV and 0.52 eV as the Pb concentration x is changed from 0.16 to 0.84. The room temperature dc resistivity of the films increases with T s and decreases with increase in Pb concentration x. The variation of resistivity is explained on the basis of a predominant grain boundary conduction mechanism.