A systematic study of the nitridation of SnO 2 nanowires grown by the vapor liquid solid mechanism

Abstract

SnO 2 nanowires (NWs) with diameters of 50 nm and lengths ≥10 μm have been grown at 800 °C on 1.0 nm Au/Si(001) via the vapor liquid solid mechanism and the low pressure chemical vapor deposition. These exhibited clear peaks in the X-ray diffraction corresponding to the tetragonal rutile crystal structure of SnO 2 and a broad-symmetric photoluminescence (PL) spectrum, centered around 560 nm due to structural-related defect states, energetically located in the upper half-band-gap of SnO 2. We find that post-growth thermal annealing of the SnO 2 NWs over a broad range of temperatures, i.e. 4001000 °C and high flow of O 2 does not change their crystal structure or optical properties. In contrast the nitridation of SnO 2 NWs using NH 3 leads to their elimination above 500 °C. Lower temperatures did not favor the nitridation even using extended nitridation times, hydrogen, lower ramp rates or a two-step-temperature process which are effective in the case of In 2O 3 and Ga 2O 3. However the nitridation of SnO 2 NWs was promoted by HCl, supplied in-situ via the sublimation of NH 4Cl, which reacts with Sn and SnO 2 leading to the formation of the intermediate SnCl 4, which reacts in turn with NH 3 giving tin nitride at temperatures between 400 and 500 °C. We discuss the effect of the nitridation and thermal annealing on the PL spectra. © 2011 Elsevier B.V. All rights reserved.