Core-level photoemission study of the InAs/CdSe nanocrystalline system

We have applied the technique of core-level photoemission spectroscopy with synchrotron radiation to a study of the interface in the colloidally prepared InAs/CdSe core/shell nanocrystal system. We find that As-Se and In-Se chemical bonds dominate the interface which we may describe as ``Se rich.'' The surface states observed for In and As of the pure InAs nanocrystals are successfully removed by growth of the CdSe shell layer. We discuss how the removal of these ``surface charge traps'' causes a large increase in the photoluminescence yield compared with that of the pure InAs nanocrystal.