On the Origin of Surface Traps in Colloidal II–VI Semiconductor Nanocrystals

Abstract

One of the greatest challenges in the field of semiconductor nanomaterials is to make trap-free nanocrystalline structures to attain a remarkable improvement of their optoelectronic performances. In semiconductor nanomaterials, a very high number of atoms is located on the surface and these atoms form the main source of electronic traps. The relation between surface atom coordination and electronic structure, however, remains largely unknown. Here, we use density functional theory to unveil the surface structure/electronic property relations of zincblende II–VI CdSe model nanocrystals, whose stoichiometry and surface termination agree with recent experimental findings. On the basis of the analysis of the surface geometry and the recent classification of the ligand surface coordination in terms of L-, X-, and Z-type ligands, we show that, contrary to expectations, most under-coordinated “dangling” atoms do not form traps and that L- and X-type ligands are benign to the nanocrystal electronic structure. On ...