Thermal stability of W1 − xSixSi multilayer reflective coatings under high intensity excimer laser pulses

UHV e-beam evaporated W1 − xSixSi multilayers (MLs) with four different compositions (x = 0, 0.33, 0.5 and 0.66) were XeCl laser irradiated at different fluences F ≤ 0.6 J cm−2 with number of pulses N ≤ 100. The samples were analyzed by soft X-ray reflectivity, X-ray diffraction and resistometry measurements. It was shown, that the hardness of the samples against laser irradiation increases with increasing x up to x = 0.5, then goes down again. This behavior is explained by the interplay of the suppression of the interdiffusion at the interfaces of MLs with increasing content of Si in W and the gradual decrease of the refractory nature of W when it is diluted by Si.