Revealing the Quasi-Periodic Crystallographic Structure of Self-Assembled SnTiS₃ Misfit Compound

Abstract

Chemical vapor transport synthesis of SnTiS 3 yields a self-assembled heterostructure of two distinct constituent materials, the semiconductor SnS and the semimetal TiS 2 . 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.

Thermally Activated Photoluminescence Induced by Tunable Interlayer Interactions in Naturally Occurring van der Waals Superlattice SnS/TiS2

“…The most prominent peak is situated at approximately 31.1°, corresponding to the (008) plane. Thus, this observation confirms the periodic length of the lattice to be 11.92 Å, approaching the 13.33 Å value obtained from our calculations and prior reports . The HRTEM image clearly depicts the neat arrangement of the atoms on the top surface.…”

“…Thus, this observation confirms the periodic length of the lattice to be 11.92 Å, approaching the 13.33 Å value obtained from our calculations and prior reports. 39 The HRTEM image clearly depicts the neat arrangement of the atoms on the top surface. The lattice spacing corresponding to the (100) plane have a measured value of 0.28 Å.…”

Band gap engineering by cationic substitution in Sn(Zr1−xTix)Se3 alloy for bottom sub-cell application in solar cells

“…This implied that the unknown phase of Sn-Ti-Se could exist, similarly, as it was reported for the Sn-Ti-S system: Sn 1.2 Ti 0.8 S 3 in a needle-like phase 30 and (SnS) 1.2 (TiS 2 ) in a mist phase. 31 However, by analysing the chemical composition of multiple grains/domains comprising Sn, Ti and Se in sample A10, we did not nd the composition that would be typical or representative of A 1.2 B 0.8 X 3 or (AX) 1.2 (BX 2 ) stoichiometry (Fig. S2b, ESI †).…”

Engineering Natural Layered Framework for Low and Anisotropic Thermal Conductivity

“…The original (PbSe) 5 (Bi 2 Se 3 ) 3 compound is different from the misfit layered compounds like (SnS) 1.17 (NbS 2 ) n [27] with interlayer bonds and forced commensurability. [37,47,52] It's the special vdW bonding in the latter makes a layers amount of scatterings possible, [59] and causes incoherent phonon transport in an atomically sharp superlattice [27] . The vdW misfit compounds are however particular.…”

“…Wavelength of Debye–frequency phonons $$\lambda _D\!=\!\frac{hV_a}{k_B\Theta }$$ is 4.93 Å being a reference of interatomic distance and wavelength lowerlimit. (Figure 5h) Unlike vdW material having random stackings, [ 30,59 ] layers are actually bonded in undoped sample, although inherent defects [ 39 ] greatly scatter phonons. Phonon mean free path l is still larger than short wavelengths, with only part of phonons localized.…”