Origin of enhanced conductivity in low dose ion irradiated oxides

Abstract

Significant resistivity variations have previously been observed in oxides subjected to relatively low ion irradiation doses, nominally insufficient to generate the amount of bulk defects needed to explain the phenomena. In an effort to unveil the underlying mechanisms, we performed a systematic comparative study of the resistivity evolution in In2O3-based oxides as a function of low ion doses and ultraviolet (UV) illumination, observing striking correlations. Specifically, we found that irradiation with ∼3 × 1012 Si/cm2 and ∼18 h UV exposure result in similar resistivity drops, interpreted in terms of irradiation/illumination assisted desorption of oxygen containing species from the surface. This was further proven by post-irradiation exposure of one of the samples to an oxygen atmosphere partially restoring the resistivity. Combining the present results with literature data, we conclude that the radiation tolerance of In2O3-based and similar oxides depends on the surface charge modifications, individual defect contributions, and contributions from defect complexes at low, intermediate, and high doses, respectively.