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

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.

arXiv comment15 pages, 6 figures

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• Van der Waals solid phase epitaxy to grow large-area manganese-doped MoSe${}_2$ few-layers on SiO${}_2$/Si
• Electron and thermal transport via Variable Range Hopping in MoSe${}_2$ single crystals
• Photoluminescence efficiency of MBE-grown MoSe${}_2$ monolayers featuring sharp excitonic lines and diverse grain structures
• Epitaxy of new layered materials: 2D chalcogenides and challenges of weak van der Waals interactions