Seminars Archive

Resonant Photoelectron Spectroscopy of Transition Metal Dichalcogenides

Abstract
Intercalation of dichalcogenides of titanium TiX2, X = S, Se, Te leads to hybridization of valence states of intercalated metal with states of atoms belonging to the host lattice. As a rule these hybridized states contribute in near-Fermi states of the valence band. So they play an important role in transport, magnetic, mechanic and other physical properties of the materials. ARPES with UV exiting radiation gives detailed information concerning these states. This technique with high energy resolution is successfully used for study of an electronic structure of TiX2 and intercalates based on TiX2. However, only exceptionally it is possible to find an orbital symmetry of the bands because of low energy of exiting radiation. Resonant XPS using synchrotron radiation has lower energy resolution in comparison with UPS but is fast and simple method for determination of energy and orbital symmetry of bands. We apply this technique for study near-Fermi band structure solid solution with substitution CrxTi1-хSe2 and intercalation compounds CuxTiSe2. According our previous results the substitution of Ti by Cr in 1T — TiSe2 leads to formation of structural fragments 1T — CrSe2. Using resonant XPS of chromium valence band the strong narrow Cr 3d band in a vicinity of the Fermi level is found. Energy splitting ~1 eV for Cr 2p3/2 XPS caused by exchange magnetic interaction of Cr 3d electrons and core 2p vacancies was experimentally found. This splitting together with theoretical calculation of DOS in 1T — CrSe2 point the half-metal character of spin- polarized Cr 3d density of states. Resonant XPS of Cu3d states for CuxTiSe2 shows many-particle effects which indicate long-living exited states of Cu atom, probably due to weak interaction between Cu and host lattice.