Synthesis of Large Area Two-Dimensional MoS₂ Films by Sulfurization of Atomic Layer Deposited MoO₃ Thin Film for Nanoelectronic Applications

The feasibility of growing atomically thin MoS₂ films (down to two monolayers) on several tens of cm² area was demonstrated by first depositing the MoO₃ thin film by using an atomic layer deposition and subsequent sulfurization at temperatures ranging from 500 to 1000 °C. The effect of sulfurization temperature on properties of thin MoS₂ films was investigated in details. It was found that the annealing of the MoO₃ film under the elemental sulfur vapor condition allows effective sulfurization from 500 °C, at which the converted MoS₂ film contained a rather high concentration of elemental sulfur which might reside at the boundaries between the relatively low-crystallized edge-on MoS₂ grains. The increase in sulfurization temperature from 500 to 1000 °C results in a significant grain size growth from ∼10 up to >∼100 nm, with the change of the edge-on grains to the flat grains with their (0001) planes being parallel to the sapphire substrate. Raman spectroscopy investigations also indicated that the defect concentration decreased with the increasing sulfurization temperature. The films obtained by the sulfurization at lower temperatures (500–700 °C) may have high catalytic activity, whereas the highly (0001) aligned films obtained at higher temperatures (900–1000 °C) could be useful for high functionality electronic applications, which was successfully demonstrated by their combination with thin ferroelectric HfO₂-based film. Thus, the noticeable remnant polarization value and a good switching endurance were obtained directly in contact with MoS₂ film, allowing to conclude the possibility of the memory MoS₂-based FeFET concept realization.