Electrical conductivity and electric polarization in In2O3 − δ: Sr at different oxygen contents

Abstract

The electrical characteristics of strontium-doped indium oxide have been experimentally investigated in the case of deviations from the stoichiometric composition with respect to oxygen. Doping considerably decreases the electrical conductivity of In2O3 and makes it extremely highly sensitive to variations in the oxygen content. A small oxygen deficiency of the samples corresponds to the high-resistance state, which is formed as a result of the decrease in the concentration of charge carriers and the transparency of potential barriers at the grain boundaries. It has been found that the oxygen deficiency in In2O3 − δ: Sr restores a high n-type electrical conductivity, which is consistent with the concepts of oxygen vacancies as shallow donors. For a sufficient oxygen deficiency, the potential barriers do not manifest themselves; however, as the oxygen content increases, there arises a potential relief that leads to a set of remarkable effects: the specific nonlinearity and hysteresis of the current-voltage characteristic, which are caused by the tunneling transparent potential barriers; an increase in the permittivity to 13.3 at a frequency of 105 Hz and at a temperature T = 77 K; and the temperature anomalies of the measured parameters, which are associated with the topological phase transition to a spatially inhomogeneous conductance of the samples. It has been revealed that, for small deviations from the stoichiometric composition with respect to oxygen, not only the active component but also the capacitive component of the conductance of In2O3 − δ: Sr exhibit a sensitivity to the pressure and composition of the gas medium.