Title: 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.