Synthesis of superlattices of intercalated transition metal dichalcogenides

Thin films of oriented Fe and Cr intercalated (NbSe2)(x)(TiSe2)(y) superlattices have been synthesized by controlled annealing of elementally modulated reactants. Analytic techniques have been developed to extract the average c-axis structure of the unit cell, the distribution of c-axis crystal sizes, and the distribution of structural defects from X-ray diffraction data. High-resolution synchrotron source X-ray diffraction data were collected from a [(Fe0.33NbSe2)(8)(Fe0.33TiSe2)(8)](12) Sample (i.e., 12 superlattice unit cells in the film, each cell containing 8 layers of Fe0.33NbSe2 followed by 8 layers of Fe0.33TiSe2) at three anomalously scattering wavelengths. Analysis determined structural parameters within 2% of published values fur the parent compounds, typical crystal sizes of 200-500 Angstrom, and typical coherence losses over a unit cell of +/-1%. Theoretical diffraction profiles calculated directly from the model structure are shown to agree satisfactorily with experiment. The flexibility offered by our growth technique suggests that synthesis of many such superlattices with a variety of different materials properties should be possible.