Revealing the Quasi-Periodic Crystallographic Structure of Self-Assembled SnTiS₃Misfit Compound

Chemical vapor transport synthesis of SnTiS3 yields a self-assembled heterostructure of two distinct constituent materials, the semiconductor SnS and the semimetal TiS2. The misfit layer compound, although thermodynamically stable, is structurally complex, and precise understanding of the structure is necessary for designing nanoengineered heterojunction compound devices or for theoretical studies. In our work, we reveal the unique complexity of the quasi-periodic structure of this heterostructure by systematically investigating the misfit compound using a set of advanced electron microscopy techniques. X-ray and electron diffraction patterns along with high-resolution scanning/transmission electron microscopy images obtained from different crystallographic orientations resolve the complexity of the sublattice component layer structure and reveal the uniquely bonded alignment among interlayers and a quasi-periodic arrangement of the sublayers. Density functional theory calculations embedded with the extracted structural information provide quantitative insights into the formation of self-assembled heterojunction structures where the nonpolar van der Waals interaction is found to play a dominant role in the structural alignment over the polar interlayer interaction.