THERMAL AGING OF NI C MULTILAYERS PREPARED BY PULSED-LASER DEPOSITION/

Ni/C multilayers are prepared by pulsed laser deposition with differen t laser wavelengths. Specimens providing different interface constitut ions are investigated in the initial state and after an annealing time of 20 min at temperatures between 50 and 400-degrees-C. X-ray reflect ometry and X-ray diffraction at grazing incidence of the radiation are applied for the characterization of the samples. An increase of the d ouble layer thickness with increasing temperature is observed for all multilayer samples. Generally this process starts at temperatures betw een 100 and 250-degrees-C, but the sample with graded interfaces remai n stable up to higher temperatures than those with abrupt interfaces. After heating at 400-degrees-C the initially almost amorphous nickel l ayers crystallize in a thermodynamically stable f.c.c. lattice structu re. For the sample with abrupt interfaces intermixing of nickel and ca rbon during deposition leads to the formation of crystalline nickel ca rbide between 200 and 300-degrees-C.