Ni50Nb50/C amorphous multilayers for "water window" soft X-rays - structure and stability

Amorphous Ni50Nb50/C multilayers with a period of 2.4 nm for the water wind ow soft X-rays were prepared by pulsed laser ablation deposition. The struc tural stability of these multilayers was studied by grazing incidence X-ray scattering. The multilayers were found to be highly stable at room tempera ture for periods as long as 3 years. However, the Ni50Nb50 layer was found to undergo an amorphous - crystalline disorder - order transformation due t o annealing while the carbon layer remained unchanged. The crystalline phas e after transformation could be identified as the NiNb phase. The vertical layered structure, however, was found to be highly stable even after anneal ing the multilayers at 473 and 593 K under vacuum. The multilayer period re mains unchanged till 473 K and increases by 7% on annealing at 593 K. (C) 2 001 Elsevier Science Ltd. All rights reserved.