Tubular structures from the LnS–TaS2 (Ln = La, Ce, Nd, Ho, Er) and LaSe–TaSe2 misfit layered compounds

Abstract

Nanotubular structures from a new family of misfit compounds LnS–TaS₂ with (Ln = La, Ce, Nd, Ho, Er) and LaSe–TaSe₂ (some of them not known hitherto) are reported. Stress relaxation originating from the lattice mismatch between the alternating LnS(Se) and TaS₂(Se) layers, combined with seaming of the dangling bonds in the rim, leads to the formation of a variety of nanotubular structures. Their structures are studied via scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) and selected area electron diffraction (SAED). Tubules exhibiting a single folding vector for the LnS(Se) as well as TaS₂(Se) layers were often found. The small values of the c-axis periodicities are indicative of a strong interaction between the two constituent layers which was also supported by Raman spectroscopy and theoretical calculations.