Implications of orbital hybridization on the electronic properties of doped quantum dots: the case of Cu:CdSe.
This paper investigates how chemical dopants affect the electronic properties of CdSe quantum dots (QDs) and why a model that incorporates the concepts of orbital hybridization must be used to understand these properties. Extended X-ray absorption fine structure spectroscopy measurements show that copper dopants in CdSe QDs occur primarily through a statistical doping mechanism. Ultraviolet photoemission spectroscopy (UPS) experiments provide a detailed insight on the valence band (VB) structure of doped and undoped QDs. Using UPS measurements, we are able to observe photoemission from the Cu d-levels above VB maximum of the QDs which allows a complete picture of the energy band landscape of these materials. This information provides insights into many of the physical properties of doped QDs, including the highly debated near-infrared photoluminescence in Cu doped CdSe QDs. We show that all our results point to a common theme of orbital hybridization in Cu doped CdSe QDs which leads to optically and electronically active states below the conduction band minimum. Our model is supported from current-voltage measurements of doped and undoped materials, which exhibit Schottky to Ohmic behavior with Cu doping, suggestive of a tuning of the lowest energy states near the Fermi level.
Department of Physics, Illinois Institute of Technology, Chicago, IL 60616, USA.
Joshua T
JT
Wright
Department of Physics and Astronomy, University of Maine, Orono, ME 04469, USA.
Kyle
K
Forsythe
Department of Physics and Astronomy, University of Maine, Orono, ME 04469, USA.
Jamie
J
Hutchins
Department of Physics and Astronomy, University of Maine, Orono, ME 04469, USA and Laboratory for Surface Science and Technology, University of Maine, Orono, ME 04469, USA. robert.meulenberg@maine.edu.
Robert W
RW
Meulenberg