Atom Probe Tomography Analysis of Ag Doping in 2D Layered Material (PbSe)(BiSe).

Impurity doping in two-dimensional (2D) materials can provide a route to tuning electronic properties, so it is important to be able to determine the distribution of dopant atoms within and between layers. Here we report the tomographic mapping of dopants in layered 2D materials with atomic sensitivity and subnanometer spatial resolution using atom probe tomography (APT). APT analysis shows that Ag dopes both BiSe and PbSe layers in (PbSe)(BiSe), and correlations in the position of Ag atoms suggest a pairing across neighboring BiSe and PbSe layers. Density functional theory (DFT) calculations confirm the favorability of substitutional doping for both Pb and Bi and provide insights into the observed spatial correlations in dopant locations.