High-resolution $L_{\mathrm{I}\mathrm{I}\mathrm{I},\mathrm{I}\mathrm{I}}$ absorption spectra are presented for well-characterized films of amorphous and crystalline silicon. The crystalline spectrum shows features which are related to the detailed conduction-band structure of silicon. These features are not seen for the amorphous material presumably because of the lack of long-range order. The amorphous spectrum rises less steeply than the crystalline and has a broad peak near threshold.

• Received 6 December 1971

DOI:https://doi.org/10.1103/PhysRevLett.28.497