Subkelvin tunneling spectroscopy showing Bardeen-Cooper-Schrieffer superconductivity in heavily boron-doped silicon epilayers

Scanning tunneling spectroscopies in the subkelvin temperature range were performed on superconducting silicon epilayers doped with boron in the atomic percent range. The resulting local differential conductance behaved as expected for a homogeneous superconductor, with an energy-gap dispersion below $\ifmmode\pm\else\textpm\fi{}10\mathrm{%}$. The spectral shape, the amplitude, and temperature dependence of the superconductivity gap follow the BCS model, bringing support to the hypothesis of a hole pairing mechanism mediated by phonons in the weak-coupling limit.