Superconductivity in boron-doped diamond

Here we report the experimental study of a new superconductor, B-doped diamond. Subjecting a mixture of amorphous boron with graphite to a high-temperature and high-pressure treatment, we synthesized polycrystalline boron-doped diamond samples, whose sizes were suitable for specific heat measurements. For this kind of sample, we detected two specific heat anomalies at temperatures (similar to 4 K) closely corresponding to temperatures at which the resistance and magnetic susceptibility anomalies take place. The most probable origin of these specific heat anomalies is a bimodal B distribution in polycrystalline diamond. The correlation of physical properties, such as specific heat, electrical resistivity, and magnetic susceptibility, near the superconducting transition temperature is clear evidence of bulk superconductivity in these boron-doped diamond samples. Specific features in the low frequency range of Raman spectra correlate with superconducting properties of diamond. These features help to select heavily boron-doped CVD diamond films (DF) grown on (111) natural diamond, which exhibit superconductivity. (c) 2004 Elsevier B.V. All rights reserved.