Zinc oxide nanoparticles for ultraviolet photodetection

Zinc Oxide ( ZnO ) nanoparticles were created by a top-down wet-chemistry synthesis process ( ZnO - A ) and then coated with polyvinyl-alcohol (PVA) ( ZnO - U ). In ZnO - U , strong UV emission was apparent while the parasitic green emission, which normally appears in ZnO suspensions, was suppressed. A standard lift-off process via e-beam lithography was used to fabricate a detector by evaporating Aluminum ( Al ) as ohmic electrodes on the ZnO nanoparticle film. Photoconductivity experiments showed that linear current-voltage response were achieved and the ZnO - U nanoparticles based detector had a ratio of UV photo-generated current more than 5 times better than that of the ZnO - A based detector. In addition, non-linear current-voltage responses were observed when interdigitated finger Gold ( Au ) contacts were deposited on ZnO - U . The UV generated current to dark current ratios were between 4 and 7 orders of magnitude, showing better performance than the photodetector with Al contacts. ZnO - U were also deposited on Gallium Nitride ( GaN ) and Aluminum Gallium Nitride ( AlGaN ) substrates to create spectrally selective photodetectors. The responsivity of detector based on AlGaN is twice that of commercial UV enhanced Silicon photodiodes. These results confirmed that ZnO nanoparticles coating with PVA is a good material for small-signal, visible blind, and wavelength selective UV detection.