Abstract

We report optical absorption and electroabsorption measurements on silicon microcrystallites with dimensions from 40 to 100 Å. Silicon microcrystals of well-defined dimensions were prepared by thermal annealing of periodic amorphous multilayers consisting of amorphous silicon and silicon dioxide sublayers prepared by plasma-assisted chemical vapor deposition. The crystallite size is controlled by the thickness of the amorphous silicon sublayers. This novel class of material possesses many properties intermediate between bulk crystals and disordered or amorphous materials. Optical absorption for hν < 3 eV is significantly higher than that of bulk crystals possibly due to absorption in interstitial material between crystallites. Relaxation of Δk = 0 crystal momentum rules for optical transitions leads to broadening and shift of critical points in optical modulation spectra. Quantum confinement of electronic states may also lead to energy shifts in optical spectra.

© 1987 Optical Society of America