Shape-selective synthesis and photoluminescence of SnO2 nanostructures under different catalyst conditions

We have successfully synthesized various SnO 2 nanostructures on p-type Si (100) substrates via three different processes: (1) using an as-deposited Au thin-film catalyst, (2) by adjusting the particle size of the Au catalyst via annealing treatment, and (3) without using any Au catalyst. Scanning electron microscopy images indicate that nanostructures processed by methods (1) and (2) show wire-like morphology. The rod-like nanostructures obtained under “catalyst-free” conditions in method (3) present square cross sections and faceted surfaces. Transmission electron microscopy analysis shows that the SnO 2 nanostructures obtained from processes (1) and (2) are single crystalline, while those from process (3) are polycrystalline with tetragonal SnO 2 structures. Investigations on the room-temperature photoluminescence (PL) spectra reveal that the PL intensity and energy of the individual SnO 2 nanostructures differ significantly according to the synthesis method. The SnO 2 nanostructures synthesized using the “thin-film catalyst” method show a somewhat broad blue (440 nm) and an orange (620 nm) emission peak. The PL emission of the nanomaterial obtained through the “annealed catalyst” process (2) was considerably enhanced near 620 nm. The “catalyst-free” process (3) resulted in a material with only very weak orange emission at 620 nm and without any blue emission. Based on these results, the growth, microstructure, and PL mechanism of SnO 2 nanostructures are discussed in this paper.