Scanning tunnelling microscopy of charge density waves in 1T‐TaS₂

Using a variable temperature scanning tunnelling microscope we have observed both the lattice and the triple charge density wave (CDW) in 1T‐TaS₂. We obtained images of the nearly‐commensurate (NC) phase between 350 and 200 K and the triclinic (T) phase between 220 and 280 K. We analysed the images to determine the local angle of rotation of the CDW relative to the lattice to determine if commensurate domains exist in this material. In the NC phase we do not see the hexagonal discommensurate domains proposed by Nakanishi el al. (1977), but observe a structure which is uniformly incommensurate. The orientation of the CDW relative to the lattice is observed to be locally incommensurate and to vary continuously with temperature as reported by Scruby et al. (1975). However, in the T phase we observe long narrow commensurate domains very similar to those described by Nakanishi and Shiba (1984) for this phase. 1988 Blackwell Science Ltd