PERIOD EXPANSION OF CO C AND CON/CN SOFT-X-RAY MULTILAYERS AFTER ANNEALING/

Period expansion of Co/C and CoN/CN soft x-ray multilayers has been in vestigated by x-ray diffraction and Raman spectroscopy. Below the anne al temperature of 400 degrees C, the period expansion (< 12%) of Co/C multilayers is mainly caused by the graphitization of the amorphous ca rbon layers. By 500 degrees C, the crystallization and agglomeration o f Co layers induce an enormous period expansion (similar to 40%). The period expansion of CoN/CN multilayers is only 4% at 400 degrees C, wh ich is much smaller than that of Co/C multilayers. The interface patte rns of the CoN/CN multilayers still exist even if they were annealed a t 700 degrees C. The Raman spectroscopy analyses indicate that the for mation of the sp(3) bonding can be suppressed effectively by doping N atoms, and thus the period expansion is decreased considerably at anne aling temperatures below 600 degrees C. The significant suppression of grain growth above 600 degrees C is believed to be attributed to the coexistence of hcp and fcc Co structures induced by interstitial N ato ms, which cause the high-temperature period expansion decrease. The re sults also imply that the structural stability of Co/C soft x-ray mult ilayers can be significantly improved through doping N atoms. (C) 1997 American Institute of Physics.