Grain boundary effect on the superconducting transition of microcrystalline boron-doped diamond films

Microcrystalline boron-doped diamond (BDD) films were prepared on silicon substrates by hot-filament chemical vapor deposition method. Different grain sizes of the boron-doped diamond films with nearly the same boron concentration were obtained by changing the nuclei concentration on the silicon substrates. The electrical transport behaviors of as-prepared boron-doped diamond films were measured, and the results revealed that with the increase of the grain sizes on the BDD films, the superconducting transition temperature was evidently increased. This phenomenon indicates that the superconducting transition of microcrystalline BDD films is influenced by the inhomogeneity aroused by the grain boundary effect. Our results could expand our understanding of the superconducting mechanism of microcrystalline BDD films, and are also significant to conventional applications of BDD materials.

Research Highlights▶ Pre-abraded silicon substrate for boron-doped diamond film growth. ▶ Controllable grain size by using different abrading time. ▶ The film inhomogeneity depends upon the grain size and grain boundary area. ▶ Enhance of the inhomogeneity will suppress the superconducting transition.