Defect-Engineered WSe2 Surface to Improve the Growth of Semimetal-Like Sn Contact

Transition metal dichalcogenides (TMDs) are promising for further device scaling. However, their practical application is hindered by high contact resistance at the metal–TMD interface. This issue originates from the van der Waals (vdW) gap, which introduces a tunneling barrier, and from metal-induced gap states (MIGS), which lead to Fermi-level pinning (FLP). Two approaches have been proposed to reduce the contact resistance: employing semimetal electrodes to suppress MIGS and introducing chalcogen vacancies to create non-van der Waals (non-vdW) contacts. In this work, we combine these two strategies by investigating the growth of Sn, a metallic electrode that exhibits reduced FLP and semimetal-like contact behavior on the defect-engineered WSe2, a relatively p-type TMD. Defects were introduced via ion bombardment, and the control parameters of acceleration energy and ion species (Ar+ and Ne+) were systematically studied to assess their effects on defect-creation efficiency. It is found that defect density strongly depends on the bombardment conditions, with Ne+ and lower acceleration energies leading to more efficient defect formation. Furthermore, we compared the growth behavior of Sn on defective and pristine WSe2 surfaces, and Sn islands preferentially nucleate at defect sites, indicating enhanced interaction between Sn and WSe2 due to defect-mediated nucleation. These results demonstrate that defect engineering promotes Sn nucleation and the formation of a highly covered Sn layer on WSe2, providing a structural pathway toward the realization of semimetal-like contacts with reduced contact resistance in 2D semiconductor devices.