Mössbauer-Effect Studies of Lattice Dynamic Anisotropy and Line Asymmetry in Semiconductor and Organometallic–Tin Compounds

The lattice dynamic anisotropy in double-layer molecules of stannous sulfide and dioctyltinoxide was investigated in the temperature range of 60°–320°K by observing the Karyagin effect in Mössbauer doublet spectra. It was found that in molecules with a two-dimensional polymeric network the motion of the Mössbauer atom is largest in the direction perpendicular to the plane of the extended layer and that the lattice dynamic anisotropy increases at higher temperatures. The “polymer effect” enhances the recoilless fraction by restricting the motion of the molecule in the direction of the polymer bonding. An analysis for the evaluation of absolute values of the recoilless fraction has been outlined. It was shown that stannous selenide is lattice dynamically and electronically isomorphous with stannous sulfide. The observed lattice dynamic anisotropy in both SnS and SnSe would contribute to the anisotropic semiconducting behavior in these materials. It was suggested that a rigid-body treatment as applied to a layer-type structure could be extended to include the motion of atoms on the surface of small particles. A Thirring expansion analysis was used to determine the frequency moment in the high-temperature limit for SnS.