A Method Toward Fabricating Semiconducting 3R-NbS₂ Ultrathin Films

Ultrathin NbS 2 films were synthesized from sputter-deposited ultrathin Nb films on SiO 2 /Si and quartz substrates at 850 °C under sulfur vapor pressure. The structure and surface composition of the synthesized films were characterized by grazing incidence X-ray diffraction and X-ray photoelectron spectroscopy. The films have rhombohedral 3R-NbS 2 structure and are nearly stoichiometric. The optical bandgaps of ultrathin NbS 2 samples were determined from ultraviolet–visible-near–infrared spectrometry to be in the range of ∼0.43 to ∼0.90 eV and indirect. This implies that the ultrathin NbS 2 film is semiconducting and differs from the metallic nature of bulk NbS 2 . The Raman shifts show distinct Raman active modes that depend on film thickness. The simple growth method developed can be applied to other TMDCs in which the metal has a high oxide heat of formation.