Imaging microscopic electronic contrasts at the interface of single-layer WS2 with oxide and boron nitride substrates

The electronic properties of devices based on two-dimensional materials are significantly influenced by interactions with the substrate and electrode materials. Here, we use photoemission electron microscopy to investigate the real- and momentum-space electronic structures of electrically contacted single-layer WS2 stacked on hBN, SiO2, and TiO2 substrates. Using work function and X-ray absorption imaging, we single-out clean microscopic regions of each interface type and collect the valence band dispersion. We infer the alignments of the electronic bandgaps and electron affinities from the measured valence band offsets of WS2 and the three substrate materials using a simple electron affinity rule and discuss the implications for vertical band structure engineering using mixed three- and two-dimensional materials.