Molybdenum Disulphide Nanoflakes Grown by Chemical Vapour Deposition on Graphite: Nucleation, Orientation, and Charge Transfer

TL;DR

This study investigates the growth, orientation, and charge transfer properties of molybdenum disulphide nanoflakes on graphite, revealing two stable orientations and their stability, which is crucial for optoelectronic and catalytic applications.

Contribution

It provides new insights into the nucleation, orientation, and stability of MoS2 nanoflakes on graphite, combining experimental and theoretical approaches.

Findings

MoS2 flakes grow in two orientations with a 30-degree rotation.

Both orientations are stable at room temperature due to high energy barriers.

Flakes are less doped compared to exfoliated MoS2 single layers.

Abstract

Two-dimensional molybdenum disulphide on graphene grown by chemical vapour deposition is a promising van der Waals system for applications in optoelectronics and catalysis. To extend the fundamental understanding of growth and intrinsic properties of molybdenum disulphide on graphene, molybdenum disulphide on highly oriented pyrolytic graphite is a suitable model system. Here we show, experimentally and by density-functional-theory calculations, that molybdenum disulphide flakes grow in two orientations. One of the orientations is energetically preferred, the other one is rotated by 30 degree. Because of a high energy barrier confirmed by our calculations both orientations are stable at room temperature and their switching can only be forced by external stimuli, i.e. by a scanning tunneling microscope tip. Combined Kelvin probe microscopy and Raman spectroscopy measurements show that the flakes with a typical size of a few hundred nanometers are less doped than the often studied exfoliated molybdenum disulphide single layer.