Development of low carrier density graphene devices

Epitaxial graphene on SiC(0001) is used to fabricate Hall bar structures for metrological applications with a fabrication process that has been developed to eliminate organic chemical contamination of the graphene. Before any lithographic patterning a metal protection layer of 15 nm thickness is deposited on as-grown graphene. The protection layer on top of the Hall-bar area is etched by diluted fresh aqua regia at the last step of the fabrication, therefore avoiding any contamination from photoresist or photoresist remover. Results including low carrier density and high mobility are reported, along with the appearance of well-developed quantized Hall resistance plateaus for filling factor V=2 at magnetic fields as low as 2 T.