Tungsten Oxide Adhesion Layer for Low Resistance Hole Contacts to WSe₂

The dangling-bond-free surfaces of transition metal dichalcogenides (TMDs) fundamentally challenge the creation of strongly bonded metal contacts. Commonly used interfacial adhesion layers, such as titanium, have unfavorable band alignment to the valence band of TMDs. Here, we introduce tungsten oxide (WO_x) as an interfacial adhesion layer for low resistance hole contacts on monolayer WSe₂. We show that the WO_x adhesion layer exhibits a 2-fold increase in adhesion force on both WSe₂ and SiO₂ surfaces compared to the conventional titanium adhesion layer while enabling a low hole contact resistance of R_c = 0.2 kΩ·μm on monolayer WSe₂. This work provides a method to facilitate a robust and reliable way to create highly adhesive contacts on atomically smooth TMD surfaces that are suitable for large-scale integration.