Schottky enabled enhanced UV photo-detection based on vertically aligned ZnO nanowire coated with TiO2-GO nanocomposites

Here we report the UV detection properties of vertically well aligned zinc oxide (ZnO) nanowires (NWs) coated with titanium dioxide-graphene oxide (TiO2-GO) nanocomposites which are fabricated by easy, cost-effective simple chemical methods comprised of sol-gel spin coating and chemical bath deposition. The films are deposited on fluorine-doped tin oxide (FTO) coated glass substrates with varied GO content of 0 %, 5 %, 10 % and 15 %. The formation of Schottky junction is evident from the non-linear current-voltage characteristics of FTO/ZnO NWs-GO/Ag configuration. Both the ideality factor (η) and the potential barrier height of the junction decreases with increased GO content in the film. Under UV irradiation (λ∼365 nm, power 8.0 μW), the ideality factor reduces from 9.40 to 8.71 and the potential barrier height decreases from 0.54 eV to 0.49 eV when 15 % GO is incorporated in ZnO NWs-TiO2 films. The built-in electric field in the ZnO NWs/TiO2-GO nanocomposites facilitates the separation of electron-hole pairs, resulting in a significant improvement of photocurrent and high photo-responsivity of up to 13.52 A/W at low bias (0.5 V) with rapid response time (0.89 s) and fast recovery time (1.66 s). When varying concentrations of GO are added to ZnO NWs/TiO2 nanocomposites, significant improvements in responsivity, as well as quick response and recovery time, are observed. Impedance spectra are measured under dark and UV light to investigate the role of GO in modulating the electrical properties of the ZnO NWs/TiO2-GO, a suitable hybrid nanostructure for optoelectronic application.