Voltage-amplitude-controlled complementary and self-compliance bipolar resistive switching of slender filaments in Pt/HfO2/HfOx/Pt memory devices

Abstract

Complementary resistive switching (CRS) in single devices without internal electrodes is attractive in high-density memory applications because it simplifies fabrication and avoids the complicated controlling and matching needed when using two resistive switching (RS) devices, as in conventional CRS devices. To improve the performance of such devices, however, the CRS mechanism must be understood further. Here, the authors report on voltage-amplitude-controlled CRS and self-compliance opposite-polarity bipolar RS in Pt/HfO2/HfOx/Pt memory devices. In these devices, CRS showed an almost symmetrical current–voltage hysteresis loop. Both the set voltages and hopping conduction mechanism of the high resistance states in both the bipolar RS were consistent with those of the CRS. An excess current beyond Ohmic conduction appeared before the reset switching in the bipolar RS. To interpret the characteristics of the CRS and bipolar RS, the authors propose a slender conductive filament model. According to this model, a limited oxygen vacancy (Vo) source, high Vo diffusion barrier, small film thickness, and concentrated electric field all contribute to the formation of slender filaments and to CRS operations. The model also suggests that a slender filament might form in a layer of multilayer junctions, which allows for different layers to play specific roles and improve device performance.