Nanostructured amorphous SiAu alloys — Structure and atomic correlations

Nanostructured amorphous Si1−xAux alloys (0.1 ⪕ xAu ⪕ 0.35) were produced by an inert gas condensation and in situ consolidation technique. Small-angle neutron scattering (SANS), density measurements and wide-angle neutron scattering (WANS) were employed to characterize the microstructure and local atomic order. NS results are interpreted in terms of a microstructure which consists of nanometre-sized amorphous grains embedded in a matrix of lower density, formed by grain boundaries and free volumes. The relative densities depend on the average particle size, but not on the alloy composition. In all samples, the SANS intensity decreases at low Q according to a power law − Q−3.37, which is attributed to a surface fractal structure of dimension Ds = 2.63. eveals two contributions: (a) a continuously decreasing part resulting from the presence of about 10 at.% hydrogen, and (b) a modulation of the intensity as a function of the scattering angle, characteristic of amorphous material. The total pair correlation function g(R) presents maxima corresponding to the first and second atomic neighbours. Nanostructured amorphous SiAu alloys exhibit a reduced short-range order compared with systems with dense random packing of hard spheres, e.g. metallic glasses, or continuous random network structures, e.g. covalent systems.