OPTICAL-SPECTRA OF CRYSTALLINE SILICON PARTICLES EMBEDDED IN AN AMORPHOUS-SILICON MATRIX

Deuterated amorphous silicon films deposited by DC reactive magnetron sputtering were measured by Raman spectroscopy and TEM imaging. The fi lms were found to consist of silicon crystallites embedded in an amorp hous silicon matrix. The sub-band-gap optical spectra of these films w ere recorded using photocapacitance and transient photocurrent spectro scopy. These spectra reveal an amorphous silicon sub-band-gap spectrum together with a unique optical transition in the embedded c-Si partic les. This transition corresponds to valence band electrons being optic ally inserted into empty levels lying within the amorphous silicon mob ility gap. We believe these empty levels are associated either with th e conduction band of the c-Si particles or with defect states at the c rystalline-amorphous boundary. (C) 1998 Elsevier Science B.V. All righ ts reserved.