Nanoscale photocurrent mapping by current-sensing AFM

K Priya Madhuri, K Bramhaiah and Neena S John,
Mater. Res. Express 2016, 3, 035004

The electrical properties of ultra-thin films of ZnO nanoparticles and their hybrid with reduced graphene oxide (rGO), prepared at a liquid/liquid interface, are investigated. The photocurrent distribution in ZnO and rGO–ZnO films at nanoscale under UV irradiation is explored using conducting atomic force microscopy (C-AFM). At the rGO–ZnO interface, ohmic contact is achieved rather than the Schottky junction encountered in bare ZnO with a metal electrode. Enhancement of the photocurrent is observed in both cases and the photoresponse mapping by C-AFM reveals an inhomogeneous current distribution at the nanoscale that is associated with various ZnO nanostructures in the film. While a small population of the nanostructures contributes higher photocurrents in bare ZnO film, the majority of the photoresponsive ZnO nanostructures provide high photoresponse in rGO–ZnO. This nanoscale electrical study gives insights into the local current contribution from individual nanostructures toward bulk electrical properties and can aid in understanding photovoltaic device performances.