Superconductivity and Metallic Behavior in Heavily Doped Bulk Single Crystal Diamond and Novel Transportation Behavior at Graphene/Diamond Heterostructure

Abstract Owing to extremely large bandgap 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. Besides, it remains a question whether a metallic state exists for such a large bandgap semiconductor. Herein, a single crystal superconducting diamond with a Hall carrier concentration larger than 3 × 10 20 cm −3 is realized by co‐doped of boron and nitrogen, with an extremely low resistivity of 2.07 × 10 −3 Ω cm at room temperature and dominated acceptor–donor bounded exciton photoluminescence. Furthermore, it is shown that diamond can transform from superconducting to metallic state under similar carrier concentration with tuned carrier mobility degrading from 9.10 cm 2 V −1 s −1 or 5.30 cm 2 V −1 s −1 to 2.66 cm 2 V −1 s −1 or 1.34 cm 2 V −1 s −1 . Through integrating graphene on a nitrogen and boron heavily co‐doped diamond, a novel transportation behavior in the monolayer graphene similar with superconducting behavior is realized through combining Andreev reflection and exciton‐mediated superconductivity, which may reveal more interesting superconducting behavior of diamond.