Nanotubes from the Misfit Layered Compound (SmS)_1.19TaS₂: Atomic Structure, Charge Transfer, and Electrical Properties

Abstract

Misfit layered compounds (MLCs) MX-TX 2 , where M, T = metal atoms and X = S, Se, or Te, and their nanotubes are of significant interest due to their rich chemistry and unique quasi-1D structure. In particular, LnX-TX 2 (Ln = rare-earth atom) constitute a relatively large family of MLCs, from which nanotubes have been synthesized. The properties of MLCs can be tuned by the chemical and structural interplay between LnX and TX 2 sublayers and alloying of each of the Ln, T, and X elements. In order to engineer them to gain desirable performance, a detailed understanding of their complex structure is indispensable. MLC nanotubes are a relative newcomer and offer new opportunities. In particular, like WS 2 nanotubes before, the confinement of the free carriers in these quasi-1D nanostructures and their chiral nature offer intriguing physical behavior. High-resolution transmission electron microscopy in conjunction with a focused ion beam are engaged to study SmS-TaS 2 nanotubes and their cross-sections at the atomic scale. The atomic resolution images distinctly reveal that Ta is in trigonal prismatic coordination with S atoms in a hexagonal structure. Furthermore, the position of the sulfur atoms in both the SmS and the TaS 2 sublattices is revealed. X-ray photoelectron spectroscopy, electron energy loss spectroscopy, and X-ray absorption spectroscopy are carried out. These analyses conclude that charge transfer from the Sm to the Ta atoms leads to filling of the Ta 5 d z 2 level, which is confirmed by density functional theory (DFT) calculations. Transport measurements show that the nanotubes are semimetallic with resistivities in the range of 10 –4 Ω·cm at room temperature, and magnetic susceptibility measurements show a superconducting transition at 4 K.

Nanotubes and fullerene‐like nanoparticles from layered transition metal dichalcogenides: Why do they form and what is their significance?

“…Indeed, very recently nanotubes of the misfit compound (SmS) 1.19 TaS 2 were reported to exhibit superconducting transition at ca. 4 K, which is appreciably higher than that of a pure 2H−TaS 2 (<1 K) [37] . These intriguing observations and more applications are expected to come with the continued study of inorganic nanotubes.…”

“…4 K, which is appreciably higher than that of a pure 2HÀ TaS 2 (< 1 K). [37] These intriguing observations and more applications are expected to come with the continued study of inorganic nanotubes.…”

Misfit layered compounds: Unique, tunable heterostructured materials with untapped properties

“…Another example are graphene/FeCl3 heterostructures (formerly known as graphite intercalation compounds) consisting of alternating graphene and FeCl3 layers as first identified and pioneered by Ibers, et al in 1956 13 . Misfit layered compounds are thus related to other classes of heterostructured materials in that they also form large superstructures from their component materials and there can be significant modification of electronic and physical properties, as well as interactions between the component materials via interfacial processes, which can produce interesting physical phenomena [10][11][12][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] . There are significant structural distortions which further modifies the physical properties of the bulk material due to the lattice mismatch between physically dissimilar components.…”

Emerging Nonplanar van der Waals Nanoarchitectures from 2D Allotropes for Optoelectronics

“…[ 76 ] By contrast, nanotubes from misfit layered compounds (MLC) with general formula (MX) 1+ x (TX 2 ) n (M = Sn, Pb, Sb, Bi, rare‐earths, and so on, T = Ta, Nb, Ti, Cr, and so on, X = S, Se, and Te) also have asymmetric structures consisting of alternating MX layers and TX 2 layers, and they are synthesized by well‐established CVT methods, where both the strain and the elimination of dangling bonds favor their formation as well. [ 76–81 ]…”

“…[76] By contrast, nanotubes from misfit layered compounds (MLC) with general formula (MX) 1+x (TX 2 ) n (M = Sn, Pb, Sb, Bi, rare-earths, and so on, T = Ta, Nb, Ti, Cr, and so on, X = S, Se, and Te) also have asymmetric structures consisting of alternating MX layers and TX 2 layers, and they are synthesized by well-established CVT methods, where both the strain and the elimination of dangling bonds favor their formation as well. [76][77][78][79][80][81] HC-vdWHs are another nonplanar nanoarchitecture with hollow tubular geometry, generally prepared by multistep CVD (Figure 4d,e for typical TEM observation results). [68,[82][83][84][85][86][87] Specifically, the inner nanotubes are grown and serve as template core for the vdW epitaxy of the outer tubular shell.…”