Ultrahigh vacuum deposition of CdSe nanocrystals on surfaces by pulse injection

Abstract

The fabrication of thin films of colloidal semiconductor nanocrystals is attracting muchattention due to their exceptional optoelectronic properties. This requires the developmentof new methods for depositing nanocrystals under well-controlled conditions. Here, wereport the use of the pulse injection method to deposit CdSe nanocrystals under ultrahighvacuum (UHV) on clean and well-ordered surfaces. The deposition of nanocrystals has beentested by x-ray photoelectron spectroscopy (XPS) and near edge x-ray absorption finestructure spectroscopy. Special attention has been paid to the preparation of verypure solutions of CdSe nanocrystals using cadmium stearate, trioctylphosphineoxide (TOPO) and the TOP/Se adduct for the nanocrystals synthesis followed bydissolution in pentane. It has been found that CdSe nanocrystals adsorb with similarsticking coefficients on graphite, hydrogenated silicon (100) and hydrogenateddiamond (100) surfaces. Furthermore, the XPS analysis has revealed that thesurface of the CdSe nanocrystal is Cd rich, which has important consequencesfor the optical and chemical properties. This ability to deposit semiconductornanocrystals under UHV conditions on clean and well-ordered surfaces opens up newperspectives for studying in a reliable manner all their chemical, electronic and opticalproperties.