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The amorphous Nb-Ge thin films are well-known model system for experiments on fundamental properties of vortex transport. Vortex dynamics has also been studied in Ta-Ge films with columnar structure, and other refractory metal-germanium alloys are interesting in that respect, as well. We have prepared a series of Ge30-refractory metals (Nb,Mo,Ta,W)70 thin films by magnetron codeposition. The structure of the films was examined by GISAXS, and the effects of substrate type and film thickness were investigated.
In addition to the film contribution to the scattering (fringes of intensity), Mo and Nb films show strong scattering from island like structures on top of the film. These island sizes are 5 to 10 nm, and they are 10 to 20 nm apart. Furthermore, Nb films have a distinctive signal suggesting a very uniform island height (about 8nm).
Ta and W films exhibit more complex scattering patterns which could be ascribed to top few nanometers of the film having different density than the rest below.
The samples grown on amorphous substrates have more regular fringes in the scattering intensity than those grown on monocrystalline silicon and sapphire substrates. It seems that flat, monocrystalline substrate surface favours island formation during the deposition, the tendency that is conserved at least up to the film thickness of 20nm. For the films whose thickness exceeds 80 nm, the substrate influence diminishes, and the scattering from films of different composition grown on different substrate tends to reflect mainly the metal component of the alloy.
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