Identification of native defects of 1T-HfTe₂

Defects have significant impact on material properties. Identifying the atomic structure is the foundation for defect studies. Combining scanning tunneling microscopy/spectroscopy and density functional theory simulations, we have studied native defects in the transition-metal dichalcogenide 1T-HfTe₂. We find that the dominant single-atom defects are the Te vacancy, Te substitution by residual iodine, and Te substitution by residual oxygen. The defect concentrations have been estimated from the scanning tunneling microscopy images and are explained using the defect formation energies. In addition to those single-atom defects, we have also identified two types of defect complexes, which are composed of Te vacancies. Our work clarifies the defect information of 1T-HfTe₂ and thus paves the way for future studies.