Intrinsic gap states in semiconductor nanocrystals

We demonstrate the existence of intrinsic gap states in bare and capped sem iconductor nanocrystals within multiband effective mass theory. These state s originate from Shockley-like surface states which, in small nanocrystals, extend over the entire crystal volume, facilitating their observation in a bsorption as well as in photoluminescence. The conditions under which such intrinsic states might be observed are discussed in light of the theory dev eloped and analysis of the band parameters of direct gap semiconductors.