Epitaxial growth and atomic-scale study of type-II Dirac semimetal 1T-NiTe2 film

By means of molecular beam epitaxy, x-ray diffraction, transmission electron microscopy, and in situ scanning tunneling microscopy, we successfully prepare type-II Dirac semimetal 1T-NiTe2 films and investigate their surface morphology, electronic structure, and topological characteristics on the atomic scale. Atomically flat NiTe2 films can be readily prepared on SrTiO3(001) substrates at ∼210∘C. For NiTe2 multilayers (∼17 layers), the predominant surface defect is identified as intercalated Ni atoms inside the van der Waals gap. Besides, we observe spin-splitting and resonant topological surface states near EF and at ∼-0.65 eV, respectively. They are suppressed at the step edges and in ultrathin monolayer and bilayer films. By exploring the quasiparticle interference, we visualize a backscattering suppression within 140±40 meV in multilayer NiTe2, which is associated possibly with the type-II Dirac node.