Suppression of UV photoluminescence in sandwich-structured Si/C composite films

Abstract

Thin films of composite silicon/carbon (Si/C) were prepared by pulsed-laser ablation alternately on C and Si materials on a rotary target, followed by vacuum deposition of the ablated materials on an ultra-clean glass substrate. The film structure consisted of alternate nanolayers of Si nanocrystals and amorphous C, with a fairly sharp demarcation boundary between adjacent layers forming well-defined sandwich structures. At room temperature, this composite nanolayered structure was found to yield much lower photoluminescent (PL) emission in the ultra violet region (300-390 nm) in comparison with that obtained for pure Si or for Si/Al2O3 thin films (see ZHU Y., WANG H. and ONG P.P., J. Phys. D, 33 (2000) 1965, and ZHU Y. and ONG P.P., J. Phys. Condens. Matter, 13 (2001) L1). The suppression mechanism of the UV PL emission appeared to occur in the interfacial surfaces between adjacent crystalline Si and amorphous C layers. It provides a possible way to selectively filter out the usually undesirable UV component of the PL emission from the silicon nanoparticles.