Figure 4. X-ray photoelectron spectroscopy (XPS) measurements are performed to analyze the MoS₂-HfO₂ interface properties.

The deconvolution of the (a) S 2p and (b) Mo 3d spectra of the monolayer MoS₂ on HfO₂ substrate, where the binding energies of all spectra are referenced to C1s that is set to 285 eV. The doublet Mo 3d_5/2 and 3d_3/2 orbitals are found to peak at 229.77 and 232.89 eV, respectively. Whereas the spin-orbital splitting for S 2p is well resolved into S 2p_3/2 and 2p_1/2 at 162.59 and 163.81 eV, respectively, which is in good agreement with the reported binding energy values. These XPS results confirm the formation of pure 2H-MoS₂ crystal structure by magnetron sputtering approach. However, the extraction of S:Mo ratio shows a deficit value of ~1.96, which indicates sulfur deficiency at the interface.