Investigating the Work Function Evolution of WS$_{x}$Se$_{2-x}$ Alloys

Two-dimensional layered transition metal dichalcogenides (TMDs), such as WS$_{2}$ and WSe$_{2,}$ are an important class of materials because of their novel physical and electrical properties. The work function of the material can inform the choice of metal to use when making contacts and can also provide valuable information regarding the band alignment in heterostructures made of dissimilar materials. Here we present work function measurements of multi-layer WS$_{x}$Se$_{2-x}$ (x ranges from 0 to 2) sheets exfoliated from bulk alloys using Kelvin Probe Force Microscopy. Using a graphite work function W$_{G\, }=$ 4.5 eV as reference, we find the average work function of WS$_{x}$Se$_{2-x}$ to linearly interpolate between W$=$4.52 eV for WSe$_{2}$ to W$=$4.74 eV for WS$_{2}$ as x varies from 0 to 2. At every alloy composition, W varies from sheet to sheet in a range of approximately 0.15 eV. Our experimental results provide useful information to the design of transistors and heterostructures of these materials.