The UV-laser induced heating effect on photoluminescence from ZnO nanocrystals deposited on different substrates

Photoluminescence (PL) from ZnO nanocrystals deposited on silicon, sapphire and glass substrates was measured at different temperatures and UV-laser excitation densities. Our studies show that the PL properties of the nanocrystals are a strong function of the ultraviolet laser excitation density and the thermophysical properties of the substrates used. Even at low temperatures (10-30 K), high-power laser illumination can heat the top layer of nanocrystals up to 100 K. The heating effect induced by laser illumination results in a saturation behaviour of the PL intensity with increasing excitation density. It is determined that the degree of the saturation depends on the substrates' thermophysical properties.