Engineering of forming-free resistive switching characteristics in ZrO₂ films

The variation of forming-free resistive switching (RS) characteristics modulated by thermal annealing was investigated in ZrO₂ films fabricated by electron beam evaporation. A typical forming-free behavior with pristine resistance comparable to that of the high resistance state (HRS) was observed in the as-deposited devices. Whereas, the resistance was further reduced to a state with initial resistance even lower than the low resistance state (LRS) after annealing in N₂ ambient and a larger resistance ratio was verified in the annealed devices. Both devices exhibited stable bipolar RS without any forming step, which has great potential for memory applications. A possible RS mechanism associated with adjusting of oxygen vacancy formation and migration was proposed to explain these distinct forming-free behaviors. It is expected that controllable forming-free characteristics and improved device performance may be obtained by further optimizing the distribution and density of oxygen vacancies via post-annealing. (paper)