Bistability and metastability of oxygen vacancies in amorphous Al2O3: A possible origin of resistance switching mechanism

Abstract

Vacancies in oxides play important roles in material performances of electronic devices, and they are recently considered to be a source of the bistable resistance switching effects of amorphous oxides. Here, we show theoretically that an O vacancy in amorphous alumina has two distinct types of atomic and electronic structures with an energy barrier between them when neutrally charged, acting to be a microscopic switcher between deep and shallow levels in the bandgap as a bistable defect. It is also found that such a bistable switching of O vacancy states does not work in the α-Al2O3 crystal, unveiling a peculiar nature to amorphous structures.