Electronic state of nanodiamond/graphite interfaces

The electronic state of nanodiamond/graphite interfaces in samples prepared by annealing of nanodiamonds (ND) at 1150-1600 K has been probed using X-ray fluorescence spectroscopy and field-emission measurements. Comparison between C K-alpha spectra of ND before and after annealing revealed an enhancement of density of high-energy occupied states in the products. A quantum-chemical calculation using a carbon model showed that the observed states could originate from the electrons of dangling bonds produced by peeling of a graphitic shell from the (111) surface of a diamond particle. The developed graphitic layers screen the weakly bonding electrons, which results in a lowering of the efficiency of field-electron emission from the samples with an increase of annealing temperature.