摘要
Chemical conversion by atomic substitution offers a powerful route toward the creation of unusual structures and functionalities. Here, we demonstrate the progressive transformation of single-layer TiTe 2 into TiSe 2 by reaction with a Se flux in vacuum. Angle-resolved photoemission spectroscopy and scanning tunneling microscopy reveal intriguing reaction patterns involving TiSe 2 island ingrowth starting from the TiTe 2 island edges, while the band structure and core level signatures of TiSe 2 grow in intensity at the expense of those corresponding to TiTe 2 . Lattice mismatch between TiTe 2 and TiSe 2 results in misfit holes and lattice distortions over a distance behind a seamless fingerlike reaction front. The regions of TiSe 2 and TiTe 2 are distinguished by a height difference and a charge density wave (CDW) at different transition temperatures. The method of in situ chemical conversion offers opportunities for atomic-scale engineering of layered transition metal dichalcogenides that host useful properties arising from CDW, Dirac, Weyl, superconducting, spin-valley, and magnetic structures.