HOPPING CONDUCTION OF AMORPHOUS INO(X) FILMS IN THE PRESENCE OF AN ELECTRIC HARD GAP IN THE ELECTRON-DENSITY OF STATES

Abstract

Amorphous indium oxide films deep in the insulating regime, show a crossover from the Efros-Shklovskii variable-range-hopping conduction to a simple-activation conduction across a hard gap. The rigid gap, resulting from hardening of the parabolic Coulomb gap near the Fermi level, is extremely insensitive to a magnetic field, which provides strong evidence of its non-magnetic nature.