Anisotropic weakly localized transport in nitrogen-doped ultrananocrystalline diamond films

Abstract

We establish the dominant effect of anisotropic weak localization ͑WL͒ in three dimensions ͑3D͒ associated with a propagative Fermi surface on the conductivity correction in heavily nitrogen-doped ultrananocrystalline diamond ͑UNCD͒ films based on magnetoresistance 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 two-dimensional WL or strong localization regime. The corresponding dephasing time of electronic wave functions in these systems described as ϳT −p with p Ͻ 1, follows a relatively weak temperature dependence compared to the generally expected nature for bulk dirty metals having p Ն 1. The temperature dependence of Hall ͑electron͒ mobility together with an enhanced electron density has been used to interpret the unusual magnetotransport features and show delocalized electronic transport in these n-type UNCD films, which can be described as lowdimensional superlattice structures.

Anisotropic three-dimensional weak localization in ultrananocrystalline diamond films with nitrogen inclusions

“…Here, we present exactly that proposed model for the conduction in our N-UNCD films, in the context of a disordered superlattice-like structure 59 in the grain boundary. We further attempt to validate this reported 3DWL anisotropic model, used to explain the conductivity in our N-UNCD films, by investigating the temperature dependence of the phase coherence length 10,11 .…”

Field electron emission induced glow discharge in a nanodiamond vacuum diode

“…By replacing the free electron mass in this definition with effective electron mass, which was found to be as small as 1/18m 0 from transport measurements [32], one can find that the inversion temperature is 4500 K which is close to the graphite vaporization/sublimation temperature. Thus Notingham heating, never inverting into cooling under our realistic conditions, and additional Joule heating drive the nanodiamond vacuum diode into thermal runaway regime.…”

“…The use of the effective mass 1/18m 0 relies on extensive experimental evidence that field emission and photoemission take places from graphitic like grain boundaries or graphitic patches [23,33,34]. If this is the case, the effective electron mass in nanodiamond films is as small [32] as it is in graphite [35]. The observed plasma discharge stabilization for an extended period of time may be due to the fact that the surface temperature never reaches 4500 K. A somewhat lower temperature is expected due to a cooling mechanism when heavy atoms carry away significant amount of energy, i.e.…”

Effect of structural disorder and Coulomb interactions in the superconductor-insulator transition applied to boron doped diamond

“…We assume these three variations as there is as yet insufficient experimental data directly relating the change in the microstructure of BDD or BNCD to the atomic boron concentration. In the case of nitrogen incorporation in nano-diamond and amorphous carbon films, the variation of the structural disorder with nitrogen incorporation is non-linear [35][36][37][38] showing an initially rapid increase in disorder and tending towards saturation with increasing nitrogen incorporation. To isolate the effects of structural disorder, we first assume that the on-site energy at all sites is uniform.…”