Nonvolatile resistance switching in amorphous In–Zn–O films

In amorphous In–Zn–O thin films we found a polar reversible sharp transition between a high-resistance state (HRS) with insulating properties and a degenerated semiconducting or metallic low-resistance state (LRS). The switching with resistance ratio up to 103 is completely similar to the colossal electrical resistance (CER) phenomenon, discovered in the highly correlated oxides with the structure of perovskite. We suggest that the polar reversible resistance switching occurs due to the electric field induced oxygen exchange between high-resistance thin interface part and low-resistance thick bulk part of In–Zn–O. The oxygen exchange changes the donor concentration (oxygen vacancies) in the transition layer which leads to the Fermi level shift. The transition between hopping and band conductivity occurs when the Fermi level crosses the mobility edge.