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 (TiOx), molybdenum oxide (MoOx), and gold (Au). We find that TiOx based substrates yield a lower MoS2 work function than MoOx 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.