Resistive-switching memory with ultralow-power consumption is very promising technology for next-generation data storage and high-energy-efficiency neurosynaptic chips. Herein, Ta2O5−x-based multilevel memories with ultralow-power consumption and good data retention were achieved by simple Gd-doping. The introduction of a Gd ion, as an oxygen trapper, not only suppresses the generation of oxygen vacancy defects and greatly increases the Ta2O5−x resistance but also increases the oxygen-ion migration barrier. As a result, the memory cells can operate at an ultralow current of 1 μA with the extrapolated retention time of >10 years at 85 °C and the high switching speeds of 10 ns/40 ns for SET/RESET processes. The energy consumption of the device is as low as 60 fJ/bit, which is comparable to emerging ultralow-energy consumption (<100 fJ/bit) memory devices.

Resistive-switching (RS) memories with good performance and flexibility are demonstrated in p-type amorphous CuAlOx. The nature of conducting filaments (CFs) is studied via the dependence of RS behaviors on the oxygen concentration of CuAlOx. It is observed that with increasing oxygen concentration, (1) both resistance-states and switching-voltages reduce, showing an opposite trend to popular n-type oxide devices; and (2) a transition from non-degenerate to degenerate states occurs in CFs. These observations indicate that the CFs are composed of Cu-vacancy shallow acceptors. The oxygen-concentration dependence of CFs' resistance results from the change of Cu-vacancy content, rather than CFs' size or number.