Unraveling the Impurity Location and Binding in Heavily Doped Semiconductor Nanocrystals: The Case of Cu in InAs Nanocrystals

• Published in: Journal of physical chemistry. C 2013-07, Vol.117 (26), p.13688-13696
• Main Authors: Amit, Yorai, Eshet, Hagai, Faust, Adam, Patllola, Anitha, Rabani, Eran, Banin, Uri, Frenkel, Anatoly I
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Diffusion in nanoscale solids; Diffusion in solids; Electron states and collective excitations in thin films, multilayers, quantum wells, mesoscopic and nanoscale systems; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Materials science; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Physics; Quantum dots; Transport properties of condensed matter (nonelectronic)
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp4032749

The 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.