AGING EFFECT OF CO C SOFT-X-RAY MULTILAYER MIRRORS/

The effect of aging on Co/C multilayer x-ray mirrors is presented. One significant result is the enhancement of the reflectivity at grazing incidence with time for the Co/C: multilayers with C-on-top stored in air or argon and Co-on-top stored in argon. This can be interpreted in terms of a Co-C phase-reparation at Co-C interfaces due to the positi ve enthalpy of Co-C mixing. Results also show that oxidation of the su rface of Co-on-top Co/C multilayers plays an important role in the dec rease of reflectivity. The oxidation can be prevented by storing the m ultilayers in an oxygen-free atmosphere or by depositing amorphous car bon as the toy layer. The reflectivity of tarnished multilayers can be restored by removing the oxides by wet chemical methods. (C) 1997 Ame rican Institute of Physics.