Free-standing electronic character of monolayer
We have evaluated as-grown MoS2 crystals, epitaxially grown on a monocrystalline sapphire by chemical vapor deposition (CVD), with direct electronic band-structure measurements by energy-filtered k-space photoelectron emission microscopy performed with a conventional laboratory vacuum ultraviolet He I light source under off-normal illumination. The valence states of the epitaxial MoS2 were mapped in momentum space down to 7 eV below the Fermi level. Despite the high nucleation density within the imaged area, the CVD MoS2 possesses an electronic structure similar to the free-standing monolayer MoS2 single crystal, and it exhibits hole effective masses of 2.41 +/- 0.05 m(0), and 0.81 +/- 0.05 m(0), respectively, at Gamma and K high-symmetry points that are consistent with the van der Waals epitaxial growth mechanism. This demonstrates the excellent ability of the MoS2 CVD on sapphire to yield a highly aligned growth of well-stitched grains through epitaxial registry with a strongly preferred crystallographic orientation.
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Kim, H., Dumcenco, D., Frégnaux, M., Benayad, A., Chen, M.-W., Kung, Y.-C., Kis, A., & Renault, O. (2016). Free-standing electronic character of monolayer. Physical Review B, 94(8), Article 081401. https://doi.org/10.1103/PhysRevB.94.081401
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Phys. Rev. B (2016) Kim et al - Free-standing electronic character of monolayer MoS2 in van der Waals epitaxy.pdf
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