Blue-shifted stimulated emission from ZnO films deposited on SiO2 by atomic layer deposition

ZnO films were prepared by atomic layer deposition upon a SiO2 layer on a Si substrate and treated by rapid thermal annealing. The optically-pumped random lasing actions with low threshold values were observed in the ZnO films on SiO2/Si substrates. With the decrease in ZnO film thickness or the increase in post-annealing duration, the stimulated emission shifted toward the shorter wavelength and the lasing threshold increased. The results can be attributed to the inter-diffusion between ZnO and SiO2, which causes the modification of bandgap renormalization in ZnO.