Visualizing 2D semiconductor heterojunctions using Kelvin probe force microscopy

In this work, Kelvin probe force microscopy (KPFM) is explored as a tool for visualizing the electronic band alignment of 2D van der Waals heterostructures. By quantitatively mapping the work function and bandgap, KPFM reveals the suitability of transition metal dichalcogenides for novel heterojunction devices. Using KPFM, we extracted the work function as a function of gate voltage for a monolayer WSe₂ field-effect transistor with bilayer graphene contacts. Using the surface potential map obtained by KPFM, we compared the lateral built-in potential and lateral surface electric field to macroscopic device performance parameters in order to understand the limitations of the KPFM measurement technique. Furthermore, we used KPFM to explore work functions in other 2D semiconductors in order to evaluate their potential application in broken gap interfaces.