Low temperature electrical resistivity studies in lead thin films

Abstract

Thin lead films of thickness, 100 nm, 150 nm, 200 nm and 250 nm have been deposited using electron beam evaporation technique at room temperature onto glass substrates under high vacuum conditions. Films were investigated for electrical resistivity at low temperatures from 77 K to 300 K. Resistivity variation with temperature indicates transition from metallic to semiconductor behavior. Transition temperature increased with increasing film thickness. Temperature coefficient of resistance in the metallic region has been determined for all the four films. Using Arrhenius relation, activation energy for conduction in metallic region has been determined. Mott's small polaron hopping model has been employed to determine activation energy in the semiconducting region. In a film of 250 nm thick, deviation from Mott's small polaron hopping model for below 100 K was noted and that has been considered under Mott's variable range hopping model. The complete understanding of electrical properties of Pb films has been necessitated by the fact that the band gap in CdS decreases when Pb is incorporated into it, which in turn can be used to fabricated large efficient solar cells. It is for the first time that lead films of the present thickness have been investigated for low temperature resistivity. © 2013 Sumy State University.