Layer-Thickness-Dependent Work Function of MoS₂ on Metal and Metal Oxide Substrates

Transition metal dichalcogenides, such as molybdenum disulfide (MoS₂), have unique electronic and optoelectronic properties that are often altered by environmental effects, particularly substrate or contact materials. Understanding these effects is important for device design and engineering. There is limited information concerning how MoS₂ interacts with 3D semiconductors such as metal oxides. This work demonstrates the influence of substrate material and MoS₂ layer thickness on the work function of exfoliated MoS₂ flakes. Kelvin probe force microscopy is used to probe the work function of MoS₂ on titanium oxide (TiO_x), molybdenum oxide (MoO_x), and gold (Au). We find that TiO_x based substrates yield a lower MoS₂ work function than MoO_x and Au for various MoS₂ thicknesses, and that the screening lengths for each substrate are larger than 5 nm. By reporting the work function variation of MoS₂ on these substrates, this study aims to provide important insights into device design and contact engineering.