An infrared study of the superconducting diamond

When heavily doped with boron, diamond films can become superconducting with critical temperatures T-c well above 4 K. Here, we measure the reflectivity of such a film down to 5 cm(-1), by using both conventional radiation sources and Coherent Synchrotron Radiation. We thus determine the electron-phonon Eliashberg spectral function alpha F-2(omega) and the optical superconducting gap 2 Delta. We conclude that superconducting diamond behaves as a 'dirty' BCS superconductor. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.