Improvement of ultraviolet photoresponse of bent ZnO microwires by coupling piezoelectric and surface oxygen adsorption/desorption effects

Abstract

Localized ultraviolet photoresponse properties of bent ZnO microwires bridging two perfect Ohmic contacts in both atmospheric and high vacuum (8 × 10⁻⁶ torr) environments have been investigated for the first time to explore the bending strain effect on the photoelectrical properties of ZnO. It is found that the ZnO microwire has higher photoconductivity and faster rising speed when photo-excitation is localized at the bending region in an atmospheric environment, while the rising speeds are almost the same when photo-excitations are localized at the bending and straight regions under vacuum. The bending strain induced improvement of the UV photoresponse in air was well explained by considering the coupling of piezoelectric effects and the surface oxygen adsorption/desorption procedure on the bent ZnO microwire. Our results are valuable for designing and fabricating strain modulated photoelectrical micro/nano-devices.