Scanning tunnelling microscopy study of the charge-density wave in Hf-doped 1T-TaS₂

The effect of doping with Hf atoms on the nearly commensurate (NC) charge-density-wave (CDW) structures of 1T-TaS₂ was investigated using scanning tunnelling microscopy (STM) at room temperature, for levels of substitution of Hf for Ta up to 6.9%. It was found that the Hf atom introduces a point defect to the CDW superlattice at the CDW domain boundary for lower contents. For Hf contents higher than 1%, the CDW superlattice melted and a distorted structure was observed instead of the usual CDW superlattice. The change of the CDW structure observed by STM was compared with the change of the ρ-T characteristics.