Fluctuation spectroscopy as a probe of granular superconducting diamond films

We present resistance versus temperature data for a series of boron-doped nanocrystalline diamond films. Upon extracting the fluctuation conductivity near the critical temperature we observe three distinct scaling regions-three-dimensional (3D) intragrain, quasi-0D, and 3D intergrain-in confirmation of the prediction of Lerner, Varlamov, and Vinokur. The location of the dimensional crossovers between these scaling regions allows us to determine the tunneling energy and the Thouless energy directly. This is a demonstration of the use of fluctuation spectroscopy to determine the properties of a superconducting granular system.