SnO₂ crystals were fabricated by thermal evaporation of Sn powder at 900°C in an oxygen atmosphere without any catalyst. The growth time was varied in a range of 1 ~ 3 h in order to investigate the morphological change during growth of the crystals. Scanning electron microscopy, X-ray diffractometry, energy dispersive X-ray spectroscopy, and cathodoluminescence spectroscopy were used to characterize the morphologies, crystal structures, and luminescence properties of the SnO₂ crystals. X-ray diffraction analysis showed that the SnO₂ crystals had a rutile crystallographic structure. When the growth time was 1 h, SnO₂ microrods with a rough surface were observed. With an increase of the growth time to 2 h, many nanowires on the SnO₂ microrods such that microrod-nanowire assembly had a cactus-like appearance. When the growth time was further increased to 3 h, micro/nanowires were observed. A strong visible emission peak centered at about 480 nm was observed in the room temperature cathodoluminescence spectra of all the samples.

Keywords: Tin powder, Thermal evaporation, Tin oxide micro-rods, Cactus shape