  The electronic structure of an atomic-layer-deposited MoS2 monolayer on SiO2
was investigated using X-ray absorption spectroscopy (XAS) and synchrotron
X-ray photoelectron spectroscopy (XPS). The angle-dependent evolution of the
XAS spectra and the photon-energy-dependent evolution of the XPS spectra were
analyzed in detail using an ab-initio electronic structure simulation. Although
similar to the theoretical spectra of an ideal free-standing MoS2 ML, the
experimental spectra exhibit features that are distinct from those of an ideal
ML, which can be interpreted as a consequence of S-O van der Waals (vdW)
interactions. The strong consensus among the experimental and theoretical
spectra suggests that the vdW interactions between MoS2 and adjacent SiO2
layers can influence the electronic structure of the system, manifesting a
substantial electronic interaction at the MoS2-SiO2 interface.
