Cathodoluminescence spectroscopy of single SnO2 nanowires and nanobelts

1D semiconducting SnO2 nanoribbons in form of nanowires and nanobelts with a lateral size ranging from 50 to 700 nm and length of several hundreds of micrometers are studied by Cathodoluminescence in the Scanning Electron Microscope and Transmission Electron Microscopy. Experimental High Angle Annular Dark Field imaging suggests compositional modulations along the (100) direction in agreement with recent theoretical predictions. Single nanobelt and nanowire cathodoluminescence spectroscopy reveals the presence of a broad emission made of two sub-bands centered at about 460 nm and 580 nm at room temperature. No near band edge emission is found. This result is assigned to a major role of surface effects with respect to bulk properties. CL spectroscopy carried out at different temperatures and Sn vapour pressure, before and after thermal treatments in Oxygen atmosphere and under electron beam irradiation show that the integrated intensity of the sole emission at 580 nm changes. A red and blue shift of about 20 urn are found respectively for the two bands by decreasing the temperature. A correlation between Oxygen vacancies and the cathodoluminescence emission peak at 580 nm is discussed.