Vapor treatment as a new method for photocurrent enhancement of UV photodetectors based on ZnO nanorods

Metal-semiconductor-metal ultraviolet photodetectors have been made with array of Zinc Oxide nanorods (ZnO NRs). The effect of glycerol/ethylene glycol (EG) vapor treatment on the photocurrent has been investigated. A hydrothermal method has been used for the growth of ZnO NRs and vapor annealing has been performed on the as-prepared ZnO NRs. The photodetectors based on treated ZnO NRs have shown photocurrent enhancement about 4.5 times higher than that of untreated ones at a bias of 5 V under UV illumination. The mechanism of photocurrent enhancement of treated ZnO NRs was investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and UV-vis spectrophotometer. The results indicate that NRs are almost similar in general appearance but different in the number density. The number densities of treated ZnO NRs increase due to the splitting of thicker NRs into the thinner ones. In vapor treatment, solvent vapor molecules can fit in between the coalescent NRs, form a crack and then split them away. The UV-vis absorption spectra of treated ZnO NRs show higher peaks in the UV region compared to untreated ones. These improvements of optical and electrical properties of ZnO NRs make them more suitable for application in UV photodetection.