Superconductive B-doped nanocrystalline diamond thin films: Electrical transport and Raman spectra

Electrical transport properties of thin boron doped nanocrystalline diamond films with thicknesses of 60–500nm have been studied. The Raman spectra measured exhibit Fano resonances, characteristic for B concentrations close to the metal-to-insulator transition. Upon increasing the B concentration, the sp2 carbon related Raman resonances vanish. In such boron-doped nanocrystalline diamond films, a positive magnetoresistance could be observed at liquid helium temperatures. The boron doped diamond films show conductivity similar to that of B-doped epitaxial diamond without any significant contribution of the grain boundary transport, leading to the superconductive transition in nanocrystalline diamond at ∼1.66K.