Evolution of Interface Structure in Ni-C Multilayers Depending on Annealing Temperature : Use of Embedded Co Sublayers-Markers

Abstract
To verify the mechanism of epitaxial self-smoothing of interfaces in Ni(Co)/C multilayers annealed at optimum temperature, Ni/C multilayers with embedded Co atoms-markers at a desired depth were studied. This depth-resolving EXAFS technique shows that mixed interfaces are separated at first stages of annealing followed by the crystallization of metal layers at the higher temperatures. The temperature of the interface separation coincides very closely with the temperature observed for a maximum multilayer reflectivity. These results are well explained by the decomposition of the metal glass-like region with carbon excess at the interface, simultaneously with coherent growth of metal (111) and graphite layers. Further bulk crystallization of the metal layers leads to the enhancement of interface roughness, and hence to a drastic decrease in reflectivity.