Electric Field Distribution within a Van der Waals Heterostructure

Van der Waals heterostructures offer a playground for optoelectronics with the promise of coupling a broad range of materials while lifting the constraints of epitaxy. Optimization of such devices also requires careful control of the spatial localization of the in-plane and out-of-plane electric field. Therefore, operando tools that give direct access to the local energy and electric field landscape are necessary. Here, we demonstrate that nanobeam X-ray photoemission imaging is an effective method to map the electric field in a 2D flake-based multielectrode transistor and a WS₂/MoSe₂ heterostructure, while the electrical biases are applied. We discuss how the shape and geometry of the flake, the electrical contacts, and the overlapping of the flakes impact the field distribution. In the region where flakes overlap, the in-plane electric field distribution aligns in the two materials, whereas the out-of-plane field distribution resulting from the gating charge injection deviates from a homogeneous distribution.