Highly-Oriented Atomically Thin Ambipolar MoSe$_2$ Grown by Molecular Beam Epitaxy

TL;DR

This paper demonstrates the growth of high-quality, atomically thin MoSe2 using molecular beam epitaxy on GaAs substrates, enabling ambipolar transport and detailed analysis of its electrical properties.

Contribution

It introduces a method for large-area, highly aligned MBE-grown MoSe2 with controllable crystalline orientation and demonstrates ambipolar transport in these films.

Findings

No intermediate compounds at the interface.

Highly aligned films with two crystalline orientations.

Ambipolar transport achieved via polymer electrolyte gating.

Abstract

Transition metal dichalcogenides (TMDCs), together with other two-dimensional (2D) materials have attracted great interest due to the unique optical and electrical properties of atomically thin layers. In order to fulfill their potential, developing large-area growth and understanding the properties of TMDCs have become crucial. Here, we used molecular beam epitaxy (MBE) to grow atomically thin MoSe$_2$ on GaAs(111)B. No intermediate compounds were detected at the interface of as-grown films. Careful optimization of the growth temperature can result in the growth of highly aligned films with only two possible crystalline orientations due to broken inversion symmetry. As-grown films can be transferred onto insulating substrates allowing their optical and electrical properties to be probed. By using polymer electrolyte gating, we have achieved ambipolar transport in MBE-grown MoSe$_2$. The temperature-dependent transport characteristics can be explained by the 2D variable-range hopping (2D-VRH) model, indicating that the transport is strongly limited by the disorder in the film.