Scanning tunneling spectroscopic studies revealed the quantum-confinement effects in Ge nanocrystals formed with ultrahigh density (> 1012 cm-2) by Ge deposition on ultrathin Si oxide films. With decreasing crystal size, the conduction band maximum upshifted and the valence band minimum downshifted. The energy shift in both cases was about 0.7 eV with the size change from 7 to 2 nm. This shows that the energy band gaps of Ge nanocrystals increased to ∼1.4 eV with decreasing size. This size dependence can be explained by the quantum-confinement effect in Ge nanocrystals.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)