  We present the first scanning tunneling spectroscopy study of
single-crystalline boron doped diamond. The measurements were performed below
100 mK with a low temperature scanning tunneling microscope. The tunneling
density of states displays a clear superconducting gap. The temperature
evolution of the order parameter follows the weak coupling BCS law with
$\Delta(0)/k_B T_c \simeq 1.74$. Vortex imaging at low magnetic field also
reveals localized states inside the vortex core that are unexpected for such a
dirty superconductor.
