Coexisting photoluminescence of Si and Ge nanocrystals in Ge/Si thin film

Abstract

Thin films of composite germanium/silicon (Ge/Si) were prepared by pulsed laser ablation alternately on Ge and Si materials on a rotary target, followed by vacuum deposition of the ablated materials on an ultraclean glass substrate. X-ray diffraction and atomic force microscopy phase analysis confirmed that the film structure consisted of a mixture of Si and Ge nanoparticles which could exist in two possible phases. Most of the particles are of less than 30 nm in diameter even after the sample was annealed at 500 °C for 6 h. With different excitation light of wavelengths 280 and 380 nm the composite film yielded independent photoluminescence emissions corresponding, respectively, to the Si and Ge nanoparticles which did not interfere with each other. These results demonstrate that there was very little interaction between the Si and Ge emissions arising from their coexisting mixture in the thin film, even after high temperature annealing of the film in the atmosphere. It opens up the possibility for application of the Si/Ge composite film in multiple function optoelectronic devices.