Semiconductor-to-metal transition in platinum dichalcogenides induced by niobium dichalcogenides

Metallizing 2D semiconductors is a crucial research area with significant applications, such as reducing the contact resistance at metal/2D semiconductor interfaces. This is a key challenge in the realization of next-generation low-power and high-performance devices. While various methods exist for metallizing Mo- and W-based 2D semiconductors like MoS₂ and WSe₂, effective approaches for Pt-based ones have been lacking. This study demonstrates that platinum dichalcogenides (PtX₂, X = Se or Te) undergo a semiconductor-to-metal transition when grown on niobium dichalcogenides (NbX₂, X = Se or Te). PtX₂/NbX₂ heterostructures were fabricated using molecular beam epitaxy (MBE) and characterized by Raman spectra, scanning transmission electron microscopy (STEM) and scanning tunneling microscopy/spectroscopy (STM/STS). Raman spectra and STEM confirm the growth of 1T-phase PtX₂ and 1H-phase NbX₂. Both 2D STS mapping and layer-dependent STS show that regardless of their layer numbers, both pristine semiconducting PtSe₂ and PtTe₂ are converted to metallic forms when interfacing with NbSe₂ or NbTe₂. Density functional theory (DFT) calculations suggest that the metallization of PtSe₂ on NbX₂ and PtTe₂ on NbTe₂ results from interfacial orbital hybridization, while for PtTe₂ on NbSe₂, it is due to the strong p-doping effect caused by interfacial charge transfer. Our work provides an effective method for metallizing PtX₂ semiconductors, which may lead to significant applications such as reducing the contact resistance at metal electrode/2D semiconductor interfaces and developing devices like rectifiers, rectenna, and photodetectors based on 2D Schottky diodes.