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Mamidanna Ramachandra Rao1 Dinesh Kumar1

1, IIT Madras, Chennai, , India

Diamond is a wide bandgap (5.5 eV) semiconductor with many attractive properties such as high directioanlity, high hardness (100 GPa) and high thermal conductivity (2000 W/mK). It shows superconductivity when doped with boron. Heavily boron doped diamond becomes a superconductor when the boron concentration is raised beyond 4.5 x 1021 cm-3. It is imperative to obtain critical information on how doping of boron in diamond changes the surface, electronic and superconducting properties in the nanocrystalline regime. Both microscopic and the macroscopic electrical measurements have been employed to study the effect of grain boundaries and of the doping level in superconducting nanocrystalline boron doped diamond (BNCD) films. Conducting atomic force microscopy (CAFM) study has been employed to investigate the local conductivity of the superconducting BNCD films (Tc = 4.3 K). CAFM study revealed that the grain boundaries are more conducting then the individual sp<span style="font-size:10.8333px">3</span> bonded grains. Probing of empty states in BNCD using X-ray absorption spectroscopy (XAS) revealed impurity band formation at 282.8 eV and 284.1 eV, above and below the valence band maximum, resepectively, which are responsible for superconductivity.

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