Structure and electrophysical properties of thin-film SnO₂–In₂O₃ heterostructures

The structure and electrical properties of In₂O₃ and SnO₂ oxide semiconductors and heterostructures based on them has been experimentally investigated. The films were prepared by the method of layer-by-layer deposition using the ion-beam sputtering. The transition from the two-phase film of amorphous SnO₂ and In₂O₃ islands, formed during the layer-by-layer deposition, to a multilayer structure consisting of the amorphous SnO₂ and In₂O₃ continuous layers occurs with an increase in the bilayer thickness. The electrophysical properties of the (SnO₂/In₂O₃)₆₉ heterostructures are determined by the transition from the random distribution of SnO₂ and In₂O₃ amorphous phases to a multilayer structure and the temperature range of measurement. For all studied systems, a consistent change in the prevailing mechanism of conductivity is observed at temperatures from 77 to 300 K. In (SnO₂/In₂O₃)₆₉ thin films with a bilayer thickness h_bl < 2.5 nm, change of the prevailing conduction mechanism takes place according to the next sequence: variable range hopping conduction over localized states near the Fermi level, hopping conduction over the nearest neighbors and hopping transfer of carriers excited into localized states near the band edges at temperatures close to room temperature.