Intercalation induced quasi-freestanding layer in TiSe2

Angle-resolved photoemission spectroscopy is employed to study the electronic structure of bulk TiSe₂ before and after doping with potassium impurities. A splitting in the conduction band into two branches is observed after room-temperature deposition. The splitting energy increases to approximately 130 meV when the sample is cooled to 40 K. One branch exhibits a nondispersive two-dimensional feature, while the other shows the characteristics of three-dimensional bulk band dispersion. Core-level spectroscopy suggests that the K impurities predominantly occupy the intercalated sites within the van der Waals gap. The results indicate the formation of a quasi-freestanding TiSe₂ layer. Additionally, doping completely suppresses the periodic lattice distortion in the surface region. These findings are further supported by density functional theory calculations, which compare the band structure of monolayer and bulk TiSe₂ with experimental data. Thus, the dimensional and intrinsic electronic properties of 1T-TiSe₂ can be controlled through the intercalation procedure used in this work.