Growth Behavior of Ni on Hydrogen-Etched WS2 Surface.

Abstract

Transition metal dichalcogenides (TMDs) are 2D materials in which the layers are stacked together by van der Waals forces. Although TMDs are expected to be promising for electronic applications, forming a uniform electrode on them is challenging because of the low adhesion forces between metals and TMDs. This study focuses on improving the quality of metal electrodes by introducing atomic H to create surface defects, using Ni on WS2 as an example. The detailed effects of H etching and subsequent Ni growth were investigated using scanning tunneling microscopy (STM) and synchrotron-based X-ray photoemission (XPS) techniques. Our studies reveal that introducing point defects of ∼3.05 × 1011 cm-2 on the WS2 surface, results in a significant shift in Ni growth from the Volmer-Weber to a near Frank-van der Merwe mode. The origin of the change is the bond formation between the Ni and W atoms, which is expected to realize ohmic contact. The optimization of metal-TMD interfaces offers valuable insights for advanced applications.