Photoluminescence and highly selective photoresponse of ZnO nanorod arrays

• Well-aligned ZnO nanorod arrays with high quality were grown on the Si substrate via a hydrothermal method.
• The green emission enhanced whereas the UV emission quenched along with the red emission after annealing in air.
• The mechanisms for the changes of emissions in PL spectra were examined.
• A new and simple approach was created to fabricate the MSM UV photodetectors based on the ZnO nanorod arrays.
• The UV photodetectors showed highly different photoresponses between short-wavelength UV and near-band-edge UV.

Well-aligned ZnO nanorod arrays were grown on the Si substrate via a hydrothermal method. Room-temperature photoluminescence (PL) measurements of the nanorods show that after annealing in air, the green emission enhances whereas the ultraviolet (UV) emission quenches along with the near-infrared emission. The mechanisms for the changes of emissions in the PL spectra were discussed and investigated. A new and simple method was created to fabricate the metal–semiconductor–metal (MSM) photodetectors based on ZnO nanorod arrays. The current–voltage (I–V) curve of the device shows double Schottky diode characteristics in the dark, and it transforms to Ohmic under UV illumination. The photogenerated current under 365-nm UV illumination is almost 25 times higher than that under 254-nm UV illumination, which is due to the easier recombination of electron–hole pairs under 254-nm UV irradiation.