Modulation structure stability of heat-treated Co/C and CoN/CN soft X-ray multilayers

Modulation structure stability of Co/C and CoN/CN soft X-ray multilayers has been investigated by X-ray diffraction and Raman spectroscopy. The graphitization of the amorphous carbon layers in Co/C multilayers causes a period expansion of 12% at annealing temperatures below 400°C. An enormous period expansion (∼40%) induced by the crystallization and agglomeration of Co layers has been observed at 500°C. While the period expansion of CoN/CN multilayers is only 4% at 400°C. The interface pattern of the CoN/CN multilayers still exists even if they were annealed at 700°C. The relatively good thermal stability of CoN/CN multilayers can be attributed to the suppression of the formation of thesp ³ bonding and, at annealing temperatures higher than the phase transition temperature of 420°C (from hcp to fcc), the coexistence of hcp- and fcc-Co structures through doping nitrogen.