Study of ruthenium film grown in oxygen environment for x-ray optics application

Ru shows high damage threshold as compared to other standard materials Au, Rh and Pt for high heat load applications in high brilliance synchrotron radiation source and x-ray free electron laser. It is also a promising candidate to be used as a protective capping layer in multilayers for increasing their life time. In the present study, Ru thin films of 500Å thickness were deposited in oxygen environment at different substrate temperatures varying from 70°C to 500°C. In reactive ion beam sputtering process, the flow of Ar and reactive O2 gas was maintained in 4:1 ratio keeping total flow 3 SCCM constant. The deposited films were characterized using grazing incidence x-ray reflectivity (GIXRR), grazing incidence x-ray diffraction (GIXRD) and secondary ion mass spectroscopy (SIMS) techniques. A significant change in GIXRR profile was observed in the sample grown at 100°C and 500°C whereas the GIXRD measurements indicated no significant formation of ruthenium oxide at different temperatures. However, a strong peak of Ru2Si3 (222) at 500°C was observed indicating a strong interfacial reaction at ruthenium/ substrate interface.The experimental data suggested a weak signature of RuO2 phase in the films deposited at RT, 70°C and 100°C and therefore the effect of ruthenium oxide with 10% composition in pure ruthenium was calculated on optical performance in extreme ultra violet region of photon energy (85-115 eV).