Individual Vanadium Dopants Form Deep In-Gap States in Monolayer WS2.

Point defects in atomically thin materials have a strong impact on physical properties, and those that induce in-gap states are advantageous for quantum information science and engineering (QISE). However, dopant engineering consisting of well-controlled synthesis and robust identification of in-gap states is challenging. In this work, we addressed this challenge by first using finely tuned chemical vapor deposition to incorporate vanadium dopants into monolayer WS2 (V-WS2). Next, we utilized a suite of scanning probe microscopy techniques to identify and characterize individual dopants. The latter included conductive atomic force microscopy (cAFM), low-temperature scanning tunneling microscopy and spectroscopy (STM/STS), and scanning transmission microscopy (STEM) and unambiguously revealed that vanadium dopants form deep in-gap states 0.35 eV above the valence band maximum (VBM) in V-WS2. Our experimental results are well supported by first-principles calculations and taken together demonstrate that V-WS2 is a promising platform for QISE applications.