Isotopic substitution of boron and carbon in superconducting diamond epilayers grown by MPCVD

International audienceSets of heavily boron-doped {100}-oriented diamond epilayers have been grown by MPCVD from isotopeenriched gases such as (13)CH(4) and (10)B(2)H(6) or (13)CH(4) and naturally abundant (11)B(2)H(6), and the resulting concentration profiles of the various boron isotopes were measured by SIMS. In the particular case of the (13)C(10)B set, the high absorption cross section of (10)B made neutron depth profiling possible for this element. The vibrational and superconducting properties of these epilayers were compared to those of films grown from gases containing the isotopes in their natural abundance. The critical temperature T(c) values were found to be lower both in the (13)C(11)B and (13)C(10)B sets, as expected for a conventional pairing mechanism mediated by phonons. In good agreement with recent studies, the isotope-effect coefficient for Tc was found to be much higher than the classical 0.5 value. Various origins for this behaviour are suggested