Thermal growth and structural and optical characterization of indium tin oxide nanopyramids, nanoislands, and tubes

In-doped SnO2 microtubes as well as Sn-doped In2O3 (ITO) nano- and microislands have been grown by thermal treatment of compacted SnO2–In2O3 powders under argon flow at 1350 °C in a catalyst-free process. The SnO2 tubes contain about 1 at. % of In, even when the In content in the starting mixture was as high as 52 at. %. However, the ITO nanoislands and nanopyramids, grown preferentially on the faces and edges of the tubes, present an In content up to six times higher than the tubes. Spatially resolved cathodoluminescence shows a higher emission from the Sn-rich structures, so that the In-rich ITO nanoislands show dark contrast in the CL images. CL spectra show that the main emission bands in both, Sn-rich and In-rich, structures, are related to oxygen deficiency. X-ray photoelectron spectroscopy shows differences between the tubes and the nanoislands in the O (1s) spectral region. In particular, a component at 531.9 eV of the O (1s) signal appears enhanced in the In-rich islands.