Optical transitions in silicon nanocrystals near structural transition region to amorphous silicon

Abstract

Employing electroreflectance (ER) spectroscopy, we have studied optical transitions in Si nanocrystals with an emphasis on the relation between the optical transition energy and the mean crystal size. The ER features are observed between 1.1 and 3.1 eV arising from the optical transitions associated with the confined electron–hole (e–h) pairs. Interestingly, the lowest optical transition energy obtained from Si nanocrystals near structural transition region to amorphous Si are smaller than that found in Si nanocrystals with a mean crystal size of 1.3 nm. A systematic explanation in terms of a simple effective mass approximation (EMA) model has been done for the behavior.