Researchers directly image how oxide coatings suppress electric fields in working graphene devices

Researchers at Sweden's Uppsala University, working with beamline scientists at Synchrotron SOLEIL in France, have directly visualized how ultrathin metal-oxide layers reshape the electric field inside operating graphene devices, a capability previously accessible only indirectly through electrical transport measurements.

Metal-oxide layers such as aluminum oxide and titanium oxide are routinely deposited on graphene to deliberately alter its electron flow, giving device designers greater control in components ranging from transistors to spin valves. Until now, understanding of how these coatings act inside a working device has relied on theoretical models, simulations and indirect electrical measurements rather than direct observation. The team used X-ray photoelectron spectroscopy to map electrical potentials across graphene devices while they were biased and operating, tracking the valence-band onset under simultaneous source-drain and gate voltage to reconstruct the in-plane field profile.