Thermal stability of soft x-ray Mo-Si and MoSi(2)-Si multilayer mirrors.

The thermal stability of Mo-Si multilayers prepared by magnetron sputtering is studied. It is found that degradation of x-ray reflectivity of Mo-Si multilayers under heat loading is connected with the roughening of Mo-Si interfaces and the formation of compounds Mo(x)Si(y),. To avoid these degradation mechanisms we fabricated and tested MoSi(2)-Si multilayers under heat loading. The MoSi(2)-Si multilayer appeared to be much more stable both in period and x-ray reflectivity because of thermodynamic equilibrium of the components MoSi(2) and Si at the interface. The working temperature of MoSi(2)-Si multilayers reaches 1000 K.