Light emission characteristics from silicon nanoparticles consisting o
f a crystalline core encased in an amorphous oxide shell are presented
. The particles were thermally oxidized in the open atmosphere at 800
degrees C for times from 5 to 160 min in order to decrease the Si core
dimensions. Photoluminescence spectra, at low excitation levels, reve
al that the light emission shifts to shorter wavelengths as the oxidat
ion time is increased. At high excitation levels, photoluminescence sp
ectra show little or no shift. These results indicate that there are a
t least two mechanisms involved with light emission from Si nanopartic
les, one associated with quantum size effects and another which is ind
ependent of size distribution. (C) 1994 American Institute of Physics.