Synthesis of superlattices of intercalated transition metal dichalcogenides

Thin films of oriented Fe and Cr intercalated (NbSe2)(x)(TiSe2)(y) superlat tices have been synthesized by controlled annealing of elementally modulate d reactants. Analytic techniques have been developed to extract the average c-axis structure of the unit cell, the distribution of c-axis crystal size s, and the distribution of structural defects from X-ray diffraction data. High-resolution synchrotron source X-ray diffraction data were collected fr om a [(Fe0.33NbSe2)(8)(Fe0.33TiSe2)(8)](12) Sample (i.e., 12 superlattice u nit cells in the film, each cell containing 8 layers of Fe0.33NbSe2 followe d 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 typic al coherence losses over a unit cell of +/-1%. Theoretical diffraction prof iles calculated directly from the model structure are shown to agree satisf actorily with experiment. The flexibility offered by our growth technique s uggests that synthesis of many such superlattices with a variety of differe nt materials properties should be possible.