Dominant conduction mechanism in TaOx-based resistive switching devices

Abstract

Temperature dependence of DC and AC conductance in Pt/TaOx/Ta2O5/Pt stacking cells is investigated to clarify conduction mechanism of TaOx-based resistive switching (RS) cells in an initial state. It is semi-quantitatively revealed that band conduction and Mott's variable range hopping are dominant at low frequency, and that small polaron tunneling is dominant at high frequency around room temperature. The cell size dependence of the cell conductance at the different frequencies indicates that introduction of a metal-rich TaOx layer forms filamentary conductive paths in a sub-stoichiometric Ta2O5 layer without applying voltage by diffusion of oxygen vacancies. The formation of conductive paths by introduction of the TaOx layer leads to forming-free RS.