Optoelectronics of Atomic Dopants in 2D Semiconductors

Substitutional doping is a versatile approach for tailoring desired functionalities in 2D semiconductors. Unlike conventional semiconductors, dopants in 2D systems often possess a high activation energy due to reduced screening, leading to apparently minor effects on the host's electronic properties, even at relatively high concentrations. In this presentation, we will delve into the distinctive impact of atomic dopants on the optical, electrical, and optoelectrical characteristics of 2D semiconductors in contrast to traditional semiconductors. As an illustrative example, we will demonstrate that a single atomic impurity significantly enhances the local out-of-plane conductivity of 2D semiconductors by up to two orders of magnitude through resonant-assisted tunnelling. This breakthrough enables the rapid quantification of selected impurities in the dilute limit (&lt;10^10 cm^(-2)) under ambient conditions, leveraging conductive atomic force microscopy [1]. Additionally, we will elucidate how atomic impurities create a narrow impurity band that facilitates in-plane conduction beyond a critical concentration. We conclude by showcasing the photovoltaic effect generated by individual atomic impurity dipoles within homobilayers of doped transition metal dichalcogenides, as observed using photoconductive atomic force microscopy.<br/>[1] Vu et al. “Single atomic point defect conductivity for dilute impurities imaging in 2D semiconductors” <i>ACS Nano</i>, 17, 15648 (2023)