Optimizing 2D-metal contact in layered Tin-selenide via native oxide modulation

The discovery of two-dimensional (2D) semiconductor has opened up new avenues for the development of short-channel field-effect transistors (FETs) with desired electrical performance. Among them, orthorhombic tin-selenide (SnSe) has garnered increasing attention due to its potential applications in a variety of electronic, optoelectronic, and thermoelectric devices. However, the realization of high-performance SnSe FETs with low contact resistance (R_c) remains a challenge. Herein, we systematically investigate the contact of few-layer SnSe FETs through the modulation of native oxide on SnSe by using different metals. It is found that chromium (Cr)-contacted devices possess the best FET performance, such as electron mobility up to 606 cm²/(V·s) at 78 K, current on/off ratio exceeding 10¹⁰, and saturation current of ~ 550 μA/μm, where a negligible Schottky barrier (SB) of ~ 30 meV and a low contact resistance of ~ 425 Ω μm are achieved. X-ray photoelectron spectroscopy (XPS) and cross-sectional electron dispersive X-ray spectroscopy (EDX) results further reveal that the improved contact arises from the Cr-induced reduction of native oxide (SnO_x) to Sn, which thins the tunneling barrier for efficient electron injection. Our findings provide a deep insight into the 2D-metal contact of SnSe and pave the way for its applications in future nanoelectronics.