Correlation of Defects and the Charge Density Wave State in Hf-Doped ZrTe₃

The transition metal tri-chalcogenide ZrTe₃ is a quasi-two-dimensional material that exhibits a unidirectional charge density wave (CDW) transition below ~ 63 K and three-dimensional superconductivity below ~ 2 K. Doping ZrTe₃ with Hf leads to a slightly higher CDW transition temperature of ~72 K (for 5% doping with Hf substituting for Zr). Here we use scanning tunneling microscopy (STM) to study Hf-doped ZrTe₃ both below and above the CDW transition temperature. We identify two main types of defects, determine their origin, and provide a quantitative approach to understand the correlation between the observed defects and CDW states with temperature.