Scanning Tunneling Microscopy of Defects in Hf-Doped ZrTe₃

ZrTe₃ is an intriguing low-dimensional material which has a crystal structure containing both one- and two-dimensional characteristics. The structure is composed of two-dimensional planes bound together by van der Waals forces. Within a layer, one-dimensional ZrTe₆ chains extend along the b-crystal axis with another set of Te-Te chains along the a-crystal axis. Despite roughly isotropic in-plane electronic conduction at room temperature, ZrTe₃ enters a unidirectional charge density wave (CDW) state below ~63 K, believed to be driven by a Fermi surface nesting of two roughly parallel Fermi surface sheets arising from the long parallel Te-Te chains along the a-crystal axis [1].

Here we present our temperature-dependent scanning tunneling microscopy (STM) measurements on Hf-doped ZrTe₃ extending from 9K (well-below the bulk CDW transition) to 91 K (above the transition). Similar to previous STM measurements [2], we identify clear defects in our topographic measurements. We detail the structural components of these observed defects and their relation to the unidirectional CDW with temperature. Our spectroscopic measurements provide insight into the impact defects have on the electronic properties of ZrTe₃.