We have evaluated as-grown $\mathrm{Mo}{\mathrm{S}}_2$ 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 $\mathrm{Mo}{\mathrm{S}}_2$ were mapped in momentum space down to 7 eV below the Fermi level. Despite the high nucleation density within the imaged area, the CVD $\mathrm{Mo}{\mathrm{S}}_2$ possesses an electronic structure similar to the free-standing monolayer $\mathrm{Mo}{\mathrm{S}}_2$ single crystal, and it exhibits hole effective masses of $2.41\pm 0.05m_0$, and $0.81\pm 0.05m_0$, respectively, at Γ and $K$ high-symmetry points that are consistent with the van der Waals epitaxial growth mechanism. This demonstrates the excellent ability of the $\mathrm{Mo}{\mathrm{S}}_2$ CVD on sapphire to yield a highly aligned growth of well-stitched grains through epitaxial registry with a strongly preferred crystallographic orientation.

• Received 24 March 2016
• Revised 8 June 2016

DOI:https://doi.org/10.1103/PhysRevB.94.081401