Structure and composition of Cu-doped CdSe nanocrystals using soft X-ray absorption spectroscopy

The local structure and composition of Cu ions dispersed in CdSe nanocrystals is examined using soft X-ray absorption near edge spectroscopy (XANES). Using Cu L-edge XANES and X-ray photoelectron measurements (XPS), we find that the Cu ions exist in the Cu(I) oxidation state. We also find that the observed Cu Ledge XANES signal is directly proportional to the molar percent of Cu present in our final material. Se Ledge XANES indicates changes in the Se density of states with Cu doping, due to a chemical bonding effect, and supports a statistical doping mechanism. Photoluminescence (PL) measurements indicate that Cu ions may act as deep electron traps. We show that XANES, XPS, and PL are a powerful combination of methods to study the electronic and chemical structure of dopants in nanostructured materials.