Local structure of Co nanocrystals embedded in hydrogenated amorphous carbon: An x-ray absorption study

Co nanocrystals embedded into a hydrogenated amorphous carbon matrix have been studied. The formation of the nanocrystals has been detected by transmission electron microscopy. The local structure of the nanocrystals was investigated by x-ray absorption fine-structure spectroscopy. We found that in as-deposited samples, Co atoms are predominantly coordinated by carbon with the fraction of Co–Co bonds increasing with an increase in the Co content. In the annealed samples, Co nanocrystals are formed with a characteristic size of 20 nm and with the structural parameters similar to that of bulk Co. About 30% of Co atoms remain bonded to the amorphous carbon matrix in the annealed sample.