Defect Engineering in Two‐Dimensional Materials: Writing, Characterization, and Device Function

Recent progress in defect engineering of two‐dimensional (2D) materials has enabled increasingly controlled routes for defect introduction, more sensitive approaches to defect characterization, and a clearer understanding of how written defect landscapes influence device behavior. This review discusses methods for defect writing, including focused ion beams, electron‐beam‐assisted processes, plasma treatment, and defect‐activated etching, together with the principal techniques used to resolve the resulting defect landscape such as Raman and photoluminescence spectroscopy, electron microscopy, atomic force microscopy, secondary‐electron imaging, and transport measurements. The effects of these defects on charge transport, photoresponse, resistive switching, and neuromorphic operation are then considered. A consistent conclusion across the literature is that device performance depends not only on defect density but also on defect type, spatial distribution, and chemical environment. More broadly, the field is shifting from viewing defects primarily as a source of degradation to using them as functional elements in 2D devices.