Local boron environment in B-doped nanocrystalline diamond films

Abstract

Thin films of heavily B-doped nanocrystalline diamond (B:NCD) have been investigated by a combination of high resolution annular dark field scanning transmission electron microscopy and spatially resolved electron energy-loss spectroscopy performed on a state-of-the-art aberration corrected instrument to determine the B concentration, distribution and the local B environment. Concentrations of $1 to 3 at.% of boron are found to be embedded within individual grains. Even though most NCD grains are surrounded by a thin amorphous shell, elemental mapping of the B and C signal shows no preferential embedding of B in these amorphous shells or in grain boundaries between the NCD grains, in contrast with earlier work on more macroscopic superconducting polycrystalline Bdoped diamond films. Detailed inspection of the fine structure of the boron K-edge and comparison with density functional theory calculated fine structure energy-loss near-edge structure signatures confirms that the B atoms present in the diamond grains are substitutional atoms embedded tetrahedrally into the diamond lattice.

Direct visualization of boron dopant distribution and coordination in individual chemical vapor deposition nanocrystalline B-doped diamond grains

“…First, recent density functional theory (DFT) ELNES calculations for single substitutional B in diamond properly reproduced the three r* peaks as well as a small pre-peak 8.7 eV before the first r* peak arising from states in the band-gap. 5 This energy position is in excellent agreement with our experimental data for pre-peak 1. Second, literature data from B-doped Fe-Cr oxide reveal a strong p* signature for B at 193.5, which is again in good agreement with our value of 193.8 eV.…”

“…Our own recent work showed that even though B was present in the amorphous grain boundaries in CVD B:NCD, no clear enrichment of the boron at grain boundaries was apparent. 5 Inside individual diamond grains, the density of extended planar lattice defects has also been shown to be considerably higher in B:NCD diamond films from CVD, an indication that B could well be enriched at planar defects and other defect centers. 6 However, the atomic scale of planar defects, the relatively low B concentration, and problems of specimen preparation for NCD films have strongly hindered the acquisition of detailed experimental data until now.…”

Surface Modifications of Nanodiamonds and Current Issues for Their Biomedical Applications

“…For example, the tetrahedral configuration can be deduced from the nitrogen K edge structure [51,60]. Recent work shows this technique permits to confirm the tetrahedral insertion of boron atoms in diamond leading to p-doping [61,62]. EELS combined with scanning TEM (STEM) can even provide mapping or profiles of impurities with an atomic resolution [63][64][65].…”

Characterization of Optical and Electrical Properties of Transparent Conductive Boron-Doped Diamond thin Films Grown on Fused Silica

“…Moreover, the extinction coefficient increased with increasing a wavelength in the wavelength region above 350 nm. This can be explained by a higher sp 2 bond content and intensive boron incorporation between the grains [61] (see Table 3. ).…”