Hopping conduction near the metal-insulator transition in amorphous indium oxide

Abstract

We present conductivity data for a range of amorphous indium oxide samples and analyse the region of activated conductivity in an attempt to identify hopping processes. The results suggest that, in highly resistive samples, conduction is by variable-range hopping in a Coulomb gap, the localized states being deep in the gap and related to the disorder. In more conductive material, there appears to be a trend towards Mott hopping as the Fermi level rises towards the conduction band.