Abstract
Metal–semiconductor contacts remain one of the key bottlenecks limiting the performance of two-dimensional transition metal dichalcogenide (TMD) devices, largely due to Fermi-level pinning (FLP) at the interface. While defect-induced gap states can be mitigated through improved fabrication, intrinsic mechanisms such as metal-induced gap states (MIGS) and interface dipoles remain difficult to suppress. In this report, I will present an STM/STS-based study of metal-surface modification as a strategy to engineer metal–TMD contacts and reduce FLP at the atomic scale.
I will first discuss the motivation for using scanning tunneling microscopy and spectroscopy to study contact physics. Besides, metal surface modification strategy is considered as a promising approach for suppressing MIGS. I then examine two initial model systems involving Se-modified Au surfaces. However, these two methods do not meet the practical conditions for device fabrication and introduce additional uncertainties.
To better reproduce realistic device fabrication conditions, I then investigated WSe₂ on Au₁₋ₓSeₓ alloy contacts. STM/STS measurements, together with theoretical calculations, show that this modified metal surface can suppress both defect-induced gap states and MIGS, shift the electronic structure toward p-type alignment, and reduce FLP. These results provide direct microscopic evidence that metal-surface engineering is an effective route for improving metal–TMD contacts and establish a basis for future work toward a broader framework for contact design.
Anyone interested is welcome to attend.