Scanning tunneling and atomic force microscopy study of the misfit layer compounds (LaS)1.14(NbS2)n (n = 1, 2) and [(Pb,Sb)S)]1.14NbS2

The misfit layer compounds (LaS)1.14(NbS)n (n = 1, 2) and [(Pb,Sb)S]1.14NbS2 were examined by scanning tunneling microscopy (STM) and atomic force microscopy (AFM). In these compounds the NaCl-type double MS (M = La, Pb, Sb) layers (Q layers) alternate with the NbS2 made up of NbS6 trigonal prisms. It was possible to record AFM and STM images for only the H layers for (LaS)1.14(NbS2)n, but for both the H and Q layers for [(Pb,Sb)S]1.14NbS2. Partial and total electron density plots of the H and Q layers were calculated to interpret the observed STM and AFM images. The bright spots in the STM and AFM images of the H layer correspond to S atoms, and those of the Q layer to Pb and Sb atoms. The STM images for the Q layers of [(Pb,Sb)S]1.14NbS2 suggest that a short-range ordering of the Pb and Sb atoms occurs in the (Pb,Sb)S sheets of the Q layer.