Figure 1: Bipolar resistive switching of Pt(TE)/a-GaO_x/ITO(BE) devices.

(a) I-V characteristics of a 90-nm a-GaO_x film during a 30-times voltage-sweep cycle of 0→+2→−2→0 V at a sweep rate v_sw=0.05 V s⁻¹ and a temperature of 25 °C. The curves measured with TE diameter=200 μm and BE area=1 × 1 cm² for the 1st sweeping cycle (yellow), 2–10th cycles (red), 11–20th cycles (blue) and 20–30th cycles (green). The numbered arrows indicate the direction of the switching cycles (counter figure-eight loops). (b) TE area scaling of the current of LRS at −1.7 V (white triangles) and HRS at +1.7 V (black triangles). The solid lines for both plots show linear scaling with a slope of 1. (c) I-V characteristics of 90 nm films measured at v_sw of 0.05 V s⁻¹ with various bias amplitudes. (d) Variable hysteretic I-V loops of a-GaO_1.1 thin films with thickness of 50 and 90 nm, measured at 25 °C with various voltage-sweep rates v_sw in the range of 0.005–500 V s⁻¹. The numbers in each graph denote the hysteretic area (V A cm⁻²) of the loop. a-GaO_x thin films can reveal non-hysteresis curves, counter figure-eight loops, triangular loops and quasi-abrupt switching-like loops as depending on v_sw.