Crystallite size-modulated exciton emission in SnO2 nanocrystalline films grown by sputtering

SnO2 nanocrystalline films with different crystallite sizes were grown by direct current sputtering. All the films show radiative recombination of free exciton (FX) and surface exciton (SX) with emission peaks varied from 330 to 338 nm and from 364 to 375 nm, respectively. The emission intensities of FX and SX versus crystallite size, excitation intensity, and temperature were also investigated. It was found that the emission intensities of both FX and SX increase with the decrease of the crystallite size of the films. In addition, the crystallite size has significant influence on the emission intensity of FX than SX. A model was also established to describe the relationship between crystallite size and excitonic emission intensity. From the temperature-dependent photoluminescence spectra, the activation energies of FX and SX are deduced.