Claim: Graphene lenses are made by sandwiching an insulating barrier of graphene sheets between two Ta2O5 sheets, where the sheets become electrically isolated and exhibited an average Fermi difference of 0.12eV when a current was passed through the bottom layer.
Evidence: implemented graphene in an infrared photodetector by sandwiching an insulating barrier of Ta2O5 between two graphene sheets. The graphene layers became electrically isolated and exhibited an average Fermi difference of 0.12eV when a current was passed through the bottom layer (figure 3).