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. [ABSTRACT FROM AUTHOR]