INTERFACE EVOLUTION AFTER THERMAL TREATMENT OF TUNGSTEN/SILICON MULTILAYERS. M.Jergel^a, V.Holy^b, Z. Bochnicek^b, E.Majkova^a, S.Luby^a, R.Senderak^{a a} Institute of Physics of the Slovak Academy of Sciences, Dubravska cesta 9, 842 28 Bratislava, Slovakia ^b Faculty of Science, Masaryk University, Kotlarska 2, 611 37 Brno, Czech Republic

The X-ray reflectivity and diffuse scattering measurements at grazing incidence after a thermal treatment were performed on the [10x(2.65nmW/9.15nmSi)] and [9x(1.7nmW/5.4nmSi)] multilayers. The samples were prepared by electron-beam evaporation in the Balzers 500 UHV apparatus onto oxidized Si(100) substrates covered with 500 nm of SiO2. The measurements were performed on the Stoe high-resolution diffractometer equipped with a double-crystal GaAs monochromator using CuK[[alpha]]1 radiation. The rapid thermal annealing was performed in a halogen lamp furnace. The reflectivity was measured also in-situ during long-time linear and isothermal annealings using a laboratory-made apparatus. The results of the reflectivity and diffuse scattering measurements were simulated within the Fresnel optical computational code and distorted-wave Born approximation, respectively, using various interface conformity models. The rms interface roughness is unchanged or even decreases up to the 500deg.C/20s annealing, the sharpening of the interfaces being accompanied by a large shift exceeding 1 nm caused by the Si diffusion into W without disturbing the multilayer structure itself. The conformity of the interface profiles and fractal behaviour found in the as-deposited state is lost after the thermal treatment and the lateral interface correlation length increases by more than one order of magnitude. An extensive interdiffusion above 500deg.C is observed leading to the breakdown of the multilayer after the 750deg.C/40s annealing. Various dynamical scattering effects at grazing incidence are discussed, too.