EFFECTS OF VACUUM ANNEALING ON THE OPTICAL-PROPERTIES OF POROUS SILICON

The effects of vacuum annealing on the optical absorption spectra in t he visible and infrared ranges, photoluminescence intensity, and conce ntration of paramagnetic centers in free-standing porous silicon films were investigated in a temperature range of 100-600 degrees C. It was found that heat-induced hydrogen desorption decreased the porous sili con band gap, which suggests that band-gap energy depends on hydrogen coverage of nanoparticles. The annealing also leads to increasing conc entration of defects that were identified as silicon dangling bonds. T he energy distribution of the dangling-bond states was estimated from the absorption spectrum. (C) 1996 American Institute of Physics.