Study of the Interface and Radial Dopant Position in Semiconductor Heterostructures Using X-ray Absorption...

Two questions that remain a challenge in the field of colloidal doped core/shell nanomaterials of different morphologies are the nature of the interface and the radial location of the dopant ion due to the diffusion within the lattice. Using a model system of Cu-doped CdSe/CdS quantum dots, we develop an in-depth understanding of the extended X-ray absorption fine structure (EXAFS) spectra of the dopant and host atoms to address both issues. Our findings suggest that the interface is not sharp, in agreement with the nonstructural studies in the literature. Local structure analysis around the Cu dopant ion confirms that Cu drifts out from the core toward the outer region in the absence of the shell but stays mostly in the core after the formation of a sufficiently thick interfacial barrier (∼2 monolayers). This study highlights the significance of EXAFS spectroscopy in understanding the nature of the interface in nanomaterials.