High resolution Rutherford backscattering spectroscopy studies on Mo/Si multilayers

High resolution Rutherford backscattering spectroscopy with an electrostatic analysis of the ion energy is applied to Mo/Si multilayers with a period of 7 nm. The multilayers have been produced for X-ray optical purposes by electron beam evaporation in ultrahigh vacuum at three different temperatures during deposition: 30, 150 and 200 °C. In the Rutherford backscattering spectra the layer structure is resolved in all three cases. The multilayers deposited at 150 and 200 °C show interlayers of mixed Mo and Si of different thicknesses on the two sides of a Mo layer. The most distinct layer structure is found for the 150 °C sample, whereas the spectra for the 30 °C sample indicate a larger interfacial roughness and those for the 200 °C sample larger interfacial layers of mixed mo and Si than for the 150 °C sample. On baking the multilayers to temperatures higher than 400 °C, interdiffusion of Mo and Si is observed. The multilayers deposited at 150 and 200 °C are destroyed after baking to 600 °C, whereas the multilayer deposited at 30 °C has already been destroyed after baking to 500 °C. Up to a baking temperature of 600 °C neither losses of material from the stack nor accumulation of Mo or Si at the surface or the interface between the stack and substrate are observed.