Mechanisms of radiation damage to Sc/Si multilayer mirrors under EUV laser irradiation

Abstract

Specific structural changes in Sc/Si multilayer mirrors irradiated with extreme ultraviolet (EUV) laser single pulses (λ = 46.9 nm) at near damage threshold fluences (0.04–0.23 J cm−2) are analysed. We have identified melting of surface layers as the basic degradation mechanism for the mirrors. Both heat generation during silicide formation and low heat conduction of the layered system significantly decreases the degradation threshold of Sc/Si multilayer mirrors compared with bulk materials. The results are relevant to the use of the multilayer mirrors for shaping and directing the intense beams produced by the new generation of coherent EUV sources