Investigation of a nanocrystalline silicon phase embedded in SiOx thin films grown by pulsed laser deposition

Abstract

The formation of nanocrystalline silicon clusters in SiOx thin films has been investigated by means of micro-Raman and Fourier transform infrared spectroscopic techniques. The samples were deposited, by means of pulsed laser ablation of a silicon target in a controlled oxygen gas environment, on substrates heated up to 883 K. Experimental results show that, by appropriately varying the deposition parameters, it is possible to achieve a fully coordinated silicon dioxide phase with the contemporary development of a nanometer-sized crystalline silicon phase and/or an amorphous one. Comparison between the effect of a relatively high substrate temperature and of a post-deposition annealing treatment have been exploited. From the line-shape analysis of the silicon TO vibrational mode Raman band, crystalline silicon volume fractions up to 90% have been estimated, while the nanocrystalline cluster sizes remained almost constant around 3.5 nm. A good agreement between our results and the predictions of silicon nanoclusters formation by a silicon atom diffusion-controlled mechanism has been found.