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Structure of Turbostratically Disordered Misfit Layer Compounds [(PbSe)0.99]1[WSe2]1, [(PbSe)1.00]1[MoSe2]1, and [(SnSe)1.03]1[MoSe2]1



The structures of three new misfit layer compounds, [(PbSe)0.99]1[WSe2]1, [(PbSe)1.00]1[MoSe2]1, and [(SnSe)1.03]1[MoSe2]1, prepared as thin films from designed elementally modulated reactant precursors, have been investigated by synchrotron X-ray diffraction and scanning transmission electron microscopy. This is the second report of a misfit layer compound based on tin selenide and the first structure determinations of tungsten- and molybdenum-containing misfit layer compounds. The compounds have mismatches in both the a- and b-axis (in-plane) lattice parameters of the component structural units, which result in misfit parameters, δ, both greater and smaller than zero. Pole figures of hk0-type reflections indicate that c-axis-oriented (basal plane) dichalcogenide-structured units are randomly oriented within the a-b plane. The widths of diffraction peaks of type hk0, 00l, and hkl (h, k ≠ 0; l ≠ 0) indicate coherence lengths of approximately (6 to 7) nm within the a-b plane, the full thickness of the film along the c-axis, and (1 to 2) nm in mixed-index directions, respectively, consistent with random rotational disorder between the constituents, commonly termed turbostratic disorder in the clay literature. The intensities of 00l- and hk0-type diffraction peaks were modeled to determine the structure of atomic planes along the c axis and the projection of the constituent structures onto the a-b plane, respectively.