Growth Behavior of\nNi on Hydrogen-Etched WS<sub>2</sub> Surface

Transition metal dichalcogenides (TMDs) are 2D materials\nin which\nthe layers are stacked together by van der Waals forces. Although\nTMDs are expected to be promising for electronic applications, forming\na uniform electrode on them is challenging because of the low adhesion\nforces between metals and TMDs. This study focuses on improving the\nquality of metal electrodes by introducing atomic H to create surface\ndefects, using Ni on WS<sub>2</sub> as an example. The detailed effects\nof H etching and subsequent Ni growth were investigated using scanning\ntunneling microscopy (STM) and synchrotron-based X-ray photoemission\n(XPS) techniques. Our studies reveal that introducing point defects\nof ∼3.05 × 10<sup>11</sup> cm<sup>–2</sup> on the\nWS<sub>2</sub> surface, results in a significant shift in Ni growth\nfrom the Volmer–Weber to a near Frank-van der Merwe mode. The\norigin of the change is the bond formation between the Ni and W atoms,\nwhich is expected to realize ohmic contact. The optimization of metal–TMD\ninterfaces offers valuable insights for advanced applications.