Identification and\nManipulation of Atomic Defects\nin Monolayer SnSe

SnSe, an environmental-friendly group-IV monochalcogenide\nsemiconductor,\ndemonstrates outstanding performance in various applications ranging\nfrom thermoelectric devices to solar energy harvesting. Its ultrathin\nfilms show promise in the fabrication of ferroelectric nonvolatile\ndevices. However, the microscopic identification and manipulation\nof point defects in ultrathin SnSe single crystalline films, which\nsignificantly impact their electronic structure, have been inadequately\nstudied. This study presents a comprehensive investigation of point\ndefects in monolayer SnSe films grown via molecular beam epitaxy.\nBy combining scanning tunneling microscopy (STM) characterization\nwith first-principles calculations, we identified four types of atomic/molecular\nvacancies, four types of atomic substitutions, and three types of\nextrinsic defects. Notably, we have demonstrated the ability to convert\na substitutional defect into a vacancy and to reposition an adsorbate\nby manipulating a single atom or molecule using an STM tip. We have\nalso analyzed the local atomic displacement induced by the vacancies.\nThis work provides a solid foundation for engineering the electronic\nstructure of future SnSe-based nanodevices.