Room temperature photo-induced phase transitions of VO2 nanodevices

Abstract

We have successfully fabricated VO₂ nanodevices using a photo-induced phase transition mechanism under an ultraviolet-light (λ = 365 nm, I = 7 μW cm⁻²). On the obtained VO₂ nanowires, the photo-induced insulator-to-metal (IM) phase transition occurred from monoclinic (insulator or semiconductor) to tetragonal (metal) structures at room temperature. The photocurrent-to-dark current ratio of the nanodevice was 285 with ultra-fast response and recovery times of 1.3 and 4.5 ms, respectively, at a UV light intensity of 7 μW cm⁻² . As the UV light intensity increased to 2.33 mW cm⁻², a maximum photocurrent-to-dark current ratio of 719 was observed. A high-resolution transmission electron microscopy (HRTEM) image indicates that the nanowires grew along the [100] axis as a single crystal. The VO₂ nanowires were then fabricated into field-effect transistor (FET) devices. High electron mobilities of 29 and 7.93 cm² V⁻¹ S⁻¹ were obtained with UV on (2.33 mW cm⁻²) and off, respectively. The electrical properties of the photo-induced IM phase transitions of the VO₂ nanowires were investigated.