Anisotropic weakly localized transport in nitrogen-doped ultrananocrystalline diamond films

We establish the dominant effect of anisotropic weak localization (WL) in three dimensions associated with a propagative Fermi surface, on the conductivity correction in heavily nitrogen doped ultrananocrystalline diamond (UNCD) films based on magneto-resistance studies at low temperatures. Also, low temperature electrical conductivity can show weakly localized transport in 3D combined with the effect of electron-electron interactions in these materials, which is remarkably different from the conductivity in 2DWL or strong localization regime. The corresponding dephasing time of electronic wavefunctions in these systems described as ~ T^-p with p < 1, follows a relatively weak temperature dependence compared to the generally expected nature for bulk dirty metals having $p \geq 1$. The temperature dependence of Hall (electron) mobility together with an enhanced electron density has been used to interpret the unusual magneto-transport features and show delocalized electronic transport in these n-type UNCD films, which can be described as low-dimensional superlattice structures.Comment: 27 pages, 6 figures, To be published in Physical Review