nl025890q_si_001.pdf (27.47 kB)
Electronic Structure and Luminescence of 1.1- and 1.4-nm Silicon Nanocrystals: Oxide Shell versus Hydrogen Passivation
journal contribution
posted on 2003-01-09, 00:00 authored by Zhiyong Zhou, Louis Brus, Richard FriesnerThe difference between oxide and hydrogen passivation of small Si nanocrystals is explored by all-electron, hybrid functional DFT calculations
with unrestricted geometry optimization. Oxide passivation lowers the band gap by about 2.4 eV for Si35 cores and by about 1.5 eV for Si66
cores. The oxide-passivated nanocrystals have optically forbidden, indirect-gap-type transitions whereas the hydrogen-passivated nanocrystals
have optically allowed, direct-gap-type transitions. The HOMO and LUMO are delocalized in both species. This result explains the experimental
observation that hydrogen-passivated Si nanocrystals luminesce in the blue whereas oxide-passivated Si nanocrystals luminesce in the yellow-red.