Characterisation of Polycrystalline thin Films of Tellurium

Abstract

Structural, electrical and optical characterisations were performed on tellurium film deposited under high vacuum conditions on ultrasonically cleaned Coming glass 7059 substrates. SEM and TEM studies reveal the polycrystalline nature of deposited tellurium films. At steady state high field conditions, space charge limited conduction is believed to have occurred due to the existence of a fast decaying density of trapping states in the energy gap. The DC conductivity is believed to exhibit a TV' 4 law dependence below room temperature, giving a value of 2x10-1 6 eV/m 3 for conduction states close to the Fermi level. From the power law dependence on frequency of AC conductivity, the barrier for bipolaron hopping is estimated to 0.33eV. Optical absorption in 9nm thick tellurium samples is due to direct transitions both allowed and forbidden producing two edges, the first one at 4eV and the other at about 0.5eV, respectively.