Superconductivity in Polycrystalline Diamond Thin Films
  Superconductivity was discovered in heavily boron-doped diamond thin films deposited by the microwave plasma assisted chemical vapor deposition (MPCVD) method. Advantages of the MPCVD deposited diamond are the controllability of boron concentration in a wide range, and a high boron concentration, especially in (111) oriented films, compared to that of the high-pressure high-temperature method. The superconducting transition temperatures are determined to be 8.7K for Tc onset and 5.0K for zero resistance by transport measurements. And the upper critical field is estimated to be around 7T. 
Yoshihiko Takano, Masanori Nagao, Tomohiro Takenouchi, Hitoshi   Umezawa, Isao Sakaguchi, Masashi Tachiki, Hiroshi Kawarada