Superconductivity and metallic behavior in heavily doped bulk single crystal diamond and graphene/diamond heterostructure

Owing to extremely large band gap of 5.5 eV and high thermal conductivity, diamond is recognized as the most important semiconductor. The superconductivity of polycrystalline diamond has always been reported, but there are also many controversies over the existence of superconductivity in bulk single crystal diamond and it remains a question whether a metallic state exists for such a large band gap semiconductor. Herein, we realize a single crystal superconducting diamond with a Hall carrier concentration larger than 3*1020 cm-3 by co-doped of boron and nitrogen. Furthermore, we show that diamond can transform from superconducting to metallic state under similar carrier concentration with tuned carrier mobility degrading from 9.10 cm2 V-1 s-1 or 5.30 cm2 V-1 s-1 to 2.66 cm2 V-1 s-1 or 1.34 cm2 V-1 s-1. Through integrating graphene on a nitrogen and boron heavily co-doped diamond, the monolayer graphene can be superconducting through combining Andreev reflection and exciton mediated superconductivity, which may intrigue more interesting superconducting behavior of diamond heterostructure.