Micro-nano scale imaging and the effect of annealing on the perpendicular structure of electrical-induced VO2 phase transition

Abstract

It was research hotspot that how to lower the threshold switching voltage (Vth), especially for the perpendicular structure of electrical-induced VO2 insulator-metal phase transition (MIT). This structure can reduce the Vth to the orders of 10−1 V. In micro-nano scale, combined with results of resistance change versus temperature, X-ray photoelectron spectroscopy measurements and conductive atomic force microscope, we had confirmed that V3+ was an important factor for electrical-induced VO2 thin MIT. On the one hand, joule heating produced by conductive V3+ region induced the surrounding VO2 region phase transition. On the other hand, with the annealing time increased from 0 min to 2 min at 470 °C in H2/N2 mixture gases, V3+ contents increased, thin film surface conductive areas increased, thin film resistance decreased, and finally resulted in threshold switching voltage decreased. Our experimental results were consistent with theory analysis. However, when the annealing time was too long (≥3 min), VO2 thin film threshold switching behavior disappeared, and current was linearly increased with voltage.