Millimeter-scale layered MoSe 2 grown on sapphire and evidence for negative magnetoresistance
Résumé
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 an application of magnetic field in the layered MoSe 2 system. This negative magnetoresistance observed at millimeter-scale is similar to that observed recently at room temperature in WS 2 flakes at a micrometer scale 1. This scalability highlights the fact that the underlying physical mechanism is intrinsic to these two-dimensional materials and occurs a very short scale.
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