Fundamental Understanding of Interface Chemistry and Electrical Contact Properties of Bi and MoS.

The interface properties and thermal stability of bismuth (Bi) contacts on molybdenum disulfide (MoS) shed light on their behavior under various deposition conditions and temperatures. The examination involves extensive techniques including X-ray photoelectron spectroscopy, scanning tunneling microscopy (STM), and scanning tunneling spectroscopy (STS). Bi contacts formed a van der Waals interface on MoS regardless of deposition conditions, such as ultrahigh vacuum (UHV, 3 × 10 mbar) and high vacuum (HV, 4 × 10 mbar), while the oxidation on MoS has been observed. However, the semimetallic properties of Bi suppress the impact of defect states, including oxidized-MoS and vacancies. Notably, the n-type characteristic of Bi/MoS remains unaffected, and no significant changes in the local density of states near the conduction band minimum are observed despite the presence of defects detected by STM and STS. As a result, the Fermi level () resides below the conduction band of MoS. The study also examines the impact of annealing on the contact interface, revealing no interface reaction between Bi and MoS up to 300 °C. These findings enhance our understanding of semimetal (Bi) contacts on MoS, with implications for improving the performance and reliability of electronic devices.