High-performing visible-blind photodetectors based on SnO/CuO nanoheterojunctions.

We report on the significant performance enhancement of SnO thin film ultraviolet (UV) photodetectors (PDs) through incorporation of CuO/SnO nanoscale heterojunctions. The nanoheterojunctions are self-assembled by sputtering Cu clusters that oxidize in ambient to form CuO. We attribute the performance improvements to enhanced UV absorption, demonstrated both experimentally and using optical simulations, and electron transfer facilitated by the nanoheterojunctions. The peak responsivity of the PDs at a bias of 0.2 V improved from 1.9 A/W in a SnO-only device to 10.3 A/W after CuO deposition. The wavelength-dependent photocurrent-to-dark current ratio was estimated to be ~ 592 for the CuO/SnO PD at 290 nm. The morphology, distribution of nanoparticles, and optical properties of the CuO/SnO heterostructured thin films are also investigated.