Atomic Defect Quantification by Lateral Force Microscopy

Atomic defects in two-dimensional (2D) materials impact electronic and optoelectronic properties, such as doping and single photon emission. An understanding of defect-property relationships is essential for optimizing material performance. However, progress in understanding these critical relationships is hindered by a lack of straightforward approaches for accurate, precise, and reliable defect quantification on the nanoscale, especially for insulating materials. Here, we demonstrate that lateral force microscopy (LFM), a mechanical technique, can observe atomic defects in semiconducting and insulating 2D materials under ambient conditions. We first improve the sensitivity of LFM through consideration of cantilever mechanics. With the improved sensitivity, we use LFM to locate atomic-scale point defects on the surface of bulk MoSe₂. By directly comparing LFM and conductive atomic force microscopy (CAFM) measurements on bulk MoSe₂, we demonstrate that point defects observed with LFM are atomic defects in the crystal. As a mechanical technique, LFM does not require a conductive pathway, which allows defect characterization on insulating materials, such as hexagonal boron nitride (hBN). We demonstrate the ability to observe intrinsic defects in hBN and defects introduced by annealing. Our demonstration of LFM as a mechanical defect characterization technique applicable to both conductive and insulating 2D materials will enable routine defect-property determination and accelerate materials research.