by electron beam irradiation*

In recent years, the trigonal-prismatic transition-metal dichalcogenides (TMDs) have been extensively studied due to a wide range of physical properties and applications. Scanning transmission electron microscopy (STEM) is a powerful tool for the investigation of material systems at the atomic level and the imaging of defect configurations. Moreover, STEM can be used to induce and modify defects. We will show that, using STEM, round multivacancy holes of various diameters and densities can be easily formed and stabilized in WSe₂, but not in other TMDs like WS₂. We report density-functional-theory (DFT) calculations to investigate the structure and stability of the observed defects in WSe₂. We construct a comprehensive model to explain how the observed stable defects form and grow in different TMDs by calculating formation energies, displacement thresholds, and electronic structures. The demonstrated control of high-density uniform multivacancies has potential for applications relating to molecular translocation.