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Unraveling the Impurity Location and Binding in Heavily Doped Semiconductor Nanocrystals: The Case of Cu in InAs Nanocrystals
journal contribution
posted on 2013-07-03, 00:00 authored by Yorai Amit, Hagai Eshet, Adam Faust, Anitha Patllola, Eran Rabani, Uri Banin, Anatoly I. FrenkelThe doping of colloidal semiconductor
nanocrystals (NCs) presents
an additional knob beyond size and shape for controlling the electronic
properties. An important problem for doping with aliovalent elements
is associated with resolving the location of the dopant and its structural
surrounding within small NCs, an issue directly connected with self-purification.
Here we used a postsynthesis diffusion-based doping method for introducing
Cu impurities into InAs quantum dots. X-ray absorption fine structure
(XAFS) spectroscopy experiments along with first-principle density
functional theory (DFT) calculations were used to probe the impurity
sites. The concentration dependence was investigated for a wide range
of doping levels, helping to derive a self-consistent picture where
the Cu impurity occupies an interstitial site within the InAs lattice.
Moreover, at extremely high doping levels, Cu–Cu interactions
are identified in the XAFS data. This structural model is supported
by X-ray diffraction data, along with the DFT calculation. These findings
establish the reproducibility of the diffusion-based doping strategy
giving rise to new opportunities of correlating the structural details
with emerging electronic properties in heavily doped NCs.