Dependence of the Superconducting Transition Temperature on the Doping Level in Single-Crystalline Diamond Films

Abstract

Homoepitaxial diamond layers doped with boron in the ${10}^{20}–{10}^{21}{\mathrm{c}\mathrm{m}}^{-3}$ range are shown to be type II superconductors with sharp transitions ($\sim 0.2\mathrm{K}$) at temperatures increasing from 0 to 2.1 K with boron contents. The critical concentration for the onset of superconductivity in those 001-oriented single-crystalline films is about $5–7{10}^{20}{\mathrm{c}\mathrm{m}}^{-3}$. The $H-T$ phase diagram has been obtained from transport and ac-susceptibility measurements down to 300 mK.