Electroreflectance study of silicon nanocrystals

Electroreflectance (ER) measurements were performed on Si nanocrystals with a crystal size of about 1–3 nm to reveal their electronic structure. Interband transitions arising from confined electron–hole (e–h) pairs were observed clearly at room temperature as the discrete features located between 1.2 and 3.1 eV. Theoretical analyses elucidated the reduced mass, kinetic energies and Coulomb attraction energies of the confined e–h pairs. Extra ER features were also observed from Si nanocrystals at 3.4 eV, indicating that E1(E0') direct gaps remain in the Si nanocrystals. Moreover, effects on ER signals of impurity doping and oxidation, which usually influence optical properties, are described. The ER technique is also applied to plasma-deposited Si thin films. Finally, an extended experimental technique, grazing-angle-incident polarized ER spectroscopy, is demonstrated.