Large-Area Synthesis of Highly Crystalline WSe₂ Monolayers and Device Applications

TLDR

Large‑area monolayer transition‑metal dichalcogenides are of great interest for valleytronics, flexible electronics, and optoelectronics, yet growing a selenide monolayer remains challenging. We aim to grow large‑area WSe₂ monolayers by activating the selenization of WO₃. Introducing hydrogen into the reaction chamber facilitates this selenization, enabling the synthesis of large‑size flakes or thin films. The resulting WSe₂ monolayers support high‑mobility ambipolar field‑effect transistors (hole mobility up to 90 cm²/Vs, electron mobility 7 cm²/Vs), can be transferred to arbitrary substrates, and enable logic circuits such as a resistor‑loaded inverter with a gain of ~13.

Abstract

The monolayer transition metal dichalcogenides have recently attracted much attention owing to their potential in valleytronics, flexible and low-power electronics, and optoelectronic devices. Recent reports have demonstrated the growth of large-size two-dimensional MoS2 layers by the sulfurization of molybdenum oxides. However, the growth of a transition metal selenide monolayer has still been a challenge. Here we report that the introduction of hydrogen in the reaction chamber helps to activate the selenization of WO3, where large-size WSe2 monolayer flakes or thin films can be successfully grown. The top-gated field-effect transistors based on WSe2 monolayers using ionic gels as the dielectrics exhibit ambipolar characteristics, where the hole and electron mobility values are up to 90 and 7 cm(2)/Vs, respectively. These films can be transferred onto arbitrary substrates, which may inspire research efforts to explore their properties and applications. The resistor-loaded inverter based on a WSe2 film, with a gain of ∼13, further demonstrates its applicability for logic-circuit integrations.