Atomic layering and misfit-induced densification at the Si(111)/In solid–liquid interface

We report on the solid–liquid interface structure between Si(111) substrates and indium at temperatures just above its melting point. At similar metal–semiconductor interfaces, liquid density enhancements have been observed by Reichert et al. [1]. Our surface x-ray diffraction study reveals that there is pronounced layering of the liquid near the interface. The data allow for identifying both layering length scales: the interlayer distance of 2.2 Å̊ and the decay length of approximately 15 Å̊. Furthermore do we find the very first layer of indium adjacent to the Si(111) to be partially laterally ordered at the substrateʹs hollow sites. We introduce a hard sphere packing model that can explain the experimentally observed layering distance and anisotropic order. This packing also reveals that due to the misfit between the size of the indium atoms and the periodicity of the substrate, the indium atoms can pack together closer than in the bulk liquid. These results show that the lateral interaction between the substrate and the liquid directly influences the layering distance and that the resulting packing can account for part of the previously observed enhanced densities.