Large-Area Epitaxial Monolayer MoS₂

TLDR

Two‑dimensional semiconductors such as MoS₂ hold promise for electronics, optoelectronics, and energy harvesting, yet controlling lattice orientation during growth remains difficult and is essential to avoid grain boundaries that degrade electrical, optical, and mechanical performance. The study aims to develop a large‑area, lattice‑orientation‑controlled growth method for high‑quality monolayer MoS₂ to enable practical applications. Monolayer MoS₂ is grown on a substrate that induces lattice alignment through van der Waals interactions, allowing the film to be readily transferred and devices to be fabricated. The epitaxial growth yields a monolayer film of coalesced single‑orientation islands that exhibit strong high‑energy optical absorbance suitable for UV photodetectors and maintain well‑connected grains with high, length‑independent mobility up to 80 μm.

Abstract

Two-dimensional semiconductors such as MoS2 are an emerging material family with wide-ranging potential applications in electronics, optoelectronics, and energy harvesting. Large-area growth methods are needed to open the way to applications. Control over lattice orientation during growth remains a challenge. This is needed to minimize or even avoid the formation of grain boundaries, detrimental to electrical, optical, and mechanical properties of MoS2 and other 2D semiconductors. Here, we report on the growth of high-quality monolayer MoS2 with control over lattice orientation. We show that the monolayer film is composed of coalescing single islands with limited numbers of lattice orientation due to an epitaxial growth mechanism. Optical absorbance spectra acquired over large areas show significant absorbance in the high-energy part of the spectrum, indicating that MoS2 could also be interesting for harvesting this region of the solar spectrum and fabrication of UV-sensitive photodetectors. Even though the interaction between the growth substrate and MoS2 is strong enough to induce lattice alignment via van der Waals interaction, we can easily transfer the grown material and fabricate devices. Local potential mapping along channels in field-effect transistors shows that the single-crystal MoS2 grains in our film are well connected, with interfaces that do not degrade the electrical conductivity. This is also confirmed by the relatively large and length-independent mobility in devices with a channel length reaching 80 μm.