Imaging and spectroscopy of artificial-atom states in core/shell nanocrystal quantum dots

Current imaging scanning tunneling microscopy is used to observe the electr onic wave functions in InAs/ZnSe core/shell nanocrystals. Images taken at a bias corresponding to the s conduction band state show that it is localize d in the central core region, while images at higher bias probing the p sta te reveal that it extends to the shell. This is supported by optical and tu nneling spectroscopy data demonstrating that the s-p gap closes upon shell growth. Shapes of the current images resemble atomlike envelope wave functi ons of the quantum dot calculated within a particle in a box model.