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Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China 3 Songshan Lake Materials Laboratory, Dongguan 523808, China 2

© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 15 May 2020 / Revised: 28 July 2020 / Accepted: 29 July 2020

ABSTRACT As an emerging two-dimensional (2D) semiconductor material, monolayer MoS2 has recently attracted considerable attention. Various promising applications of this material have been proposed for electronics, optoelectronics, sensing, catalysis, energy storage, and so on. To realize these practical applications, high-quality and large-area MoS2 with controllable properties is required. Among the many different synthesis techniques, epitaxy provides a promising route for producing MoS2 monolayers. Here, we review the epitaxial growth of monolayer MoS2 on various substrates, with a particular focus on large-scale films with large domain sizes and high domain alignments. Finally, we offer perspectives and challenges for future research and applications of this technology.

KEYWORDS monolayer MoS2, epitaxy, domain size, domain alignment, heterostructures

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Introduction

In recent years, mono- or few-layer MoS2 has been widely investigated as a typical two-dimensional (2D) transition metal dichalcogenide (TMD) and demonstrated in many interesting applications. Monolayer MoS2 consists of one-layer molybdenum atoms sandwiched by two sulfur layers and has an extreme thin thickness of about 0.65 nm with high thermal stability, chemical inertness and robust mechanical strength [1, 2]. Different from zero-energy-gap graphene, monolayer MoS2 possesses a ~ 2.2 eV direct band gap and is useful in various semiconductor devices with excellent performances [3–5]. Compared with conventional silicon-based semiconductors, monolayer MoS2 is envisioned as an alternate building block for the next-generation electronic device and integrated circuit with short channel, thin thickness, small volume, light weight, fast speed and high sensitivity. Meanwhile, the high flexibility and transparency of these monolayer films are appropriate for the realization of flexible displays and wearable electronic devices [6]. Due to the large specific surface area of this material, MoS2 monolayers also demonstrate superior sensing capabilities [7–9]. In addition, monolayer MoS2 may also be used in green electrocatalysis as its grain boundaries (GBs) and phase boundaries have been demonstrated to be active sites for hydrogen evolution reactions [10–12]. Monolayer MoS2 can be produced by a mechanical exfoliation and transfer approach. In general, as-produced flakes are suitable for the measurement of its fundamental properties and the demonstration of device applications at a small scale [2]. However, these MoS2 flakes are of limited yields, sizes, thicknesses, and locations therefore unfavorable for use i