Millimeter-scale layered MoSe2 grown on sapphire and evidence for negative magnetoresistance

TL;DR

This study demonstrates scalable growth of millimeter-scale layered MoSe2 on sapphire, revealing negative magnetoresistance and carrier hopping behavior, indicating intrinsic charge transport properties in 2D materials at large scales.

Contribution

It provides the first evidence of negative magnetoresistance in millimeter-scale MoSe2, showing that such properties are intrinsic and scalable in 2D layered materials.

Findings

Negative magnetoresistance observed at millimeter scale

Carrier transport follows two-dimensional variable range hopping

Scalable growth of MoSe2 on sapphire confirmed

Abstract

Molecular beam epitaxy technique has been used to deposit a single layer and a bilayer of MoSe 2 on sapphire. Extensive characterizations including in-situ and ex-situ measurements show that the layered MoSe 2 grows in a scalable manner on the substrate and reveals characteristics of a stoichiometric 2H-phase. The layered MoSe 2 exhibits polycrystalline features with domains separated by defects and boundaries. Temperature and magnetic field dependent resistivity measurements unveil a carrier hopping character described within two-dimensional variable range hopping mechanism. Moreover, a negative magnetoresistance was observed, stressing a fascinating feature of the charge transport under the application of a magnetic field in the layered MoSe 2 system. This negative magnetoresistance observed at millimeter-scale is similar to that observed recently at room temperature inWS2 flakes at a micrometer scale [Zhang et al., Appl. Phys. Lett. 108, 153114 (2016)]. This scalability highlights the fact that the underlying physical mechanism is intrinsic to these two-dimensional materials and occurs at very short scale.