Characterization of 1T-TiSe2 surface by means of STM and XPD experiments and model calculations

Abstract Scanning tunneling microscopy (STM) and X-ray photoelectron diffraction (XPD) are applied to study the surface of layered dichalcogenide 1 T -TiSe 2 . XPD pattern simulation for the 1 T -TiSe 2 surface is performed in the approach of electron multiple scattering within the EDAC code: considered are models of structural defects in the 1 T -TiSe 2 lattice, relaxation contraction (expansion) of surface layers and van der Waals gap, and deviation of the 1 T -TiSe 2 surface geometry from the basal plane (001). The atomic structure of 1 T -TiSe 2 surface layers is reconstructed from the XPD pattern on Se(LMM) and Ti2 p core level using the photoelectron holography scattering pattern extraction algorithm with maximum entropy method (SPEA-MEM). The results of the 3 D reconstruction are in agreement with the XPD pattern simulation data. In both cases, the TiSe 2 surface corresponds to 1 T polytype; an increase is observed in the parameter a 0 and in the van der Waals gap between two surface slabs. It is assumed that similar structural distortions of the 1 T -TiSe 2 lattice lead to the formation of an energy gap between the valence band and the conduction band of titanium diselenide, which was observed earlier by photoemission spectroscopy and follows from the theoretical calculations.