Distribution of the Pb and Sb Atoms in the (Pb, Sb)S Layers of the Franckeite-Type Misfit Compound [(Pb, Sb)S] 2.28NbS2 Examined by Scanning Tunneling and Atomic Force Microscopy

The distribution of the Pb and Sb atoms in the (Pb, Sb)S layers of the misfit compound [(Pb, Sb)S]2.28NbS2 was investigated by scanning tunneling microscopy (STM) and atomic force microscopy (AFM). This compound has NaCl-type MS (M=Pb, Sb) layers (Q-layers) alternating with NbS2 layers (H-layers) in which the Nb atoms are located in slightly distorted trigonal prism sites. Both the H- and Q-layers of [(Pb, Sb)S]2.28NbS2 were imaged by STM and AFM. The atomic-scale STM and AFM images were analyzed in terms of the partial and total electron density plots calculated for the Q- and H-layers. The STM images of the Q-layers allowed us to detect all the constitutive atoms of the Q-layers with a short-range ordering of pure Pb and Sb rows in the aQ modulation direction.