The superconductivity in boron-doped polycrystalline diamond thick films

Boron-doped polycrystalline diamond thick film was prepared by a hot filament chemical vapor deposition (HFCVD) method. The morphology and structure of the diamond were evaluated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and micro-Raman spectroscopy. The carrier concentration of the boron-doped diamond was 7.3 × 10²⁰ cm^-3, determined by a Hall measurement system. The transport measurements show that the boron-doped diamond thick film is superconductive and the superconducting transition temperatures are 10 K for T_c onset and 8.3 K for zero resistance, and there is a strong diamagnetic response in the alternating current (AC) magnetic susceptibility of the boron-doped diamond sample below 8.9 K. Such a high T_c value can be attributed to the higher efficiency of doping, contraction of the reconstructed bonds and two-dimensional nature of the surface states for diamond thick films, all together inducing a stronger electron-phonon coupling.