Electronic Structure of Silicon Nanocrystals Passivated with Nitrogen and Chlorine

The electronic structure of small (∼1 nm) silicon nanocrystals passivated with nitrogen and chlorine is explored using density funcional theory calculations. The HOMO−LUMO gap of 3.2 and 3.3 eV, calculated for the fully nitrogen [Si 35 (NH 2 ) 36 ] and chlorine passivated (Si 35 Cl 36 ) nanocrystals, respectively, correlate quite well with experimental observations describing the blue and/or white photoluminescence and electroluminescence of silicon nanocrystals, embedded in chlorinated silicon nitride films. On the other hand, the ionization energy and the electron affinity allow us to study the electron transfer properties of these systems. The charge-transfer capacity of these nanocrystals is modified in opposite directions with respect to hydrogen-passivated nanocrystals, becoming good electron acceptors with Cl passivation and good electron donors with NH 2 passivation.