LAUSR

We compared the resistive switching performances of built-in graded oxygen concentration TaOx films and uniform TaOx films under the 100 μA compliance current. The device with a graded oxygen concentration demonstrates increased low resistance and high resistance states, as well as improved stability without the need of higher switching voltages. Using the pulse mode, the switching voltages were confirmed to be less than 1.0 V for the pulse widths of 100 ns and 50 ns and less than 3.3 V for that of 10 ns, showing great advantages over previous reports. The remarkably high performances are due to the built-in oxygen concentration gradient, which results in an electric-field gradient and temperature along conduction paths, confining the rupture/reformation of the random conductive filaments to the customized highest oxygen concentration zone.