Precursor-Confined Chemical Vapor Deposition of 2D Single-Crystalline Se_<i>x</i>Te_1-<i>x</i> Nanosheets for p-Type Transistors and Inverters.

Abstract

Two-dimensional (2D) tellurium (Te) is emerging as a promising p-type candidate for constructing complementary metal-oxide-semiconductor (CMOS) architectures. However, its small bandgap leads to a high leakage current and a low on/off current ratio. Although alloying Te with selenium (Se) can tune its bandgap, thermally evaporated Se_<i>x</i>Te_1-<i>x</i> thin films often suffer from grain boundaries and high-density defects. Herein, we introduce a precursor-confined chemical vapor deposition (CVD) method for synthesizing single-crystalline Se_<i>x</i>Te_1-<i>x</i> alloy nanosheets. These nanosheets, with tunable compositions, are ideal for high-performance field-effect transistors (FETs) and 2D inverters. The preformation of Se-Te frameworks in our developed CVD method plays a critical role in the growth of Se_<i>x</i>Te_1-<i>x</i> nanosheets with high crystallinity. Optimizing the Se composition resulted in a Se_0.30Te_0.70 nanosheet-based p-type FET with a large on/off current ratio of 4 × 10⁵ and a room-temperature hole mobility of 120 cm²·V^-1·s^-1, being eight times higher than thermally evaporated Se_<i>x</i>Te_1-<i>x</i> with similar composition and thickness. Moreover, we successfully fabricated an inverter based on p-type Se_0.30Te_0.70 and n-type MoS₂ nanosheets, demonstrating a typical voltage transfer curve with a gain of 30 at an operation voltage of <i>V</i>_dd = 3 V.