Synthesis of Nb‐Doped‐WS₂–NbS₂: A Degenerate‐Semiconductor–Metal Heterostructure

Abstract

The synthesis of semiconductor–metal (S–M) heterostructures comprising semiconducting (S)‐transition metal dichalcogenides (TMDs) and metallic (M)‐TMDs via chemical vapor deposition (CVD) has emerged as a highly promising avenue for achieving low contact resistance in TMD‐based devices. However, CVD‐grown S–M heterostructures are mainly focused on non‐degenerate semiconductors, despite degenerate semiconductors also being essential for semiconductor technology, such as negative differential resistance (NDR) device. In this study, a degenerate‐S–M heterostructure, Nb‐doped‐WS2–NbS2, is synthesized via CVD with a liquid‐metal precursor. Optimizing the growth parameters, such as growth temperature, precursor ratio, and H2 content in the mixture gas, affords the desirable degenerate‐Nb‐doped‐WS2–NbS2 heterostructure. Raman and photoluminescence spectroscopies, transmission electron microscopy, and energy‐dispersive spectroscopy clearly clarify the doping signal and layer structure of the heterostructure. A growth mechanism has been proposed using in‐plane and vertical models based on structural analysis. Electrical transport measurements reveal degenerate p‐type behavior in the Nb‐doped‐WS2. In the Nb‐doped‐WS2–NbS2 degenerate‐S–M heterostructure, the device flows about twice as much on‐state current as that by an Nb‐doped‐WS2/Cr contact.