Low-temperature STM/STS studies on boron-doped (1 1 1) diamond films

We have performed scanning tunneling microscopy/spectroscopy (STM/STS) experiments on (1 1 1)-oriented epitaxial films of heavily boron-doped diamond (Tc∼5.4 K). We present that tunneling conductance spectra show temperature-dependent spatial variations. In the low-temperature region (T=0.47 K), the tunneling spectra do not show strong spatial dependence and a superconducting energy gap is observed independent of the surface morphology. In the high-temperature region (T=4.2 K), on the other hand, the tunneling conductance spectra show significant spatial dependence, indicating the inhomogeneous distribution of the superconducting property due to the distribution of boron atoms.