  The electronic properties of devices based on two-dimensional materials are
significantly influenced by interactions with substrate and electrode
materials. Here, we use photoemission electron microscopy to investigate the
real- and momentum-space electronic structures of electrically contacted
single-layer WS$_2$ stacked on hBN, SiO$_2$ and TiO$_2$ 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 band gaps and electron affinities from the
measured valence band offsets of WS$_2$ 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.
