  Epitaxial bilayer silicon oxide is a transferable two-dimensional material
predicted to be a wide band gap semiconductor, with potential applications for
deep UV optoelectronics, or as a building block of van der Waals
heterostructures. The prerequisite to any sort of such applications is the
knowledge of the electronic band structure, which we unveil using
angle-resolved photoemission spectroscopy and rationalise with the help of
density functional theory calculations. We discover dispersing bands related to
electronic delocalisation within the top and bottom planes of the material,
with two linear crossings reminiscent of those predicted in bilayer AA-stacked
graphene, and semi-flat bands stemming from the chemical bridges between the
two planes. This band structure is robust against exposure to air, and can be
controled by exposure to oxygen. We provide an experimental lower-estimate of
the band gap size of 5 eV and predict a full gap of 7.36 eV using density
functional theory calculations.
