Dislocations in diamond: Electron energy-loss spectroscopy

Electron energy-loss (EEL) spectroscopy performed near dislocation cores is one of the few experimental techniques that can yield valuable information about the electronic levels associated with dislocations. In this study, we present experimental observations of low-loss EEL spectroscopy acquired on grain boundary dislocations in a CVD diamond film. We interpret these results using ab initio calculations, where we model low-loss and core-excitation EEL spectra acquired on various dislocation cores in diamond and compare them with bulk spectra. We consider in particular the 60° glide, 60° shuffle, and 1/2[110] screw dislocations, as well as the 30° and 90° partial glide dislocations and a 90° shuffle vacancy structure. The simulations show the absence of deep gap states for the more stable partial dislocations but there are characteristic changes to the low-loss EEL spectrum in the 6-12 eV region. Such changes are consistent with experimental spectra acquired from grain boundary disocations found in boron doped CVD diamond.