iThe changes in the electronic structure and nature of the chemical bonds due to the ordering of the intercalated atoms inside the van der Waals gap were observed for the first time.
An experimental study of the electronic structure of copper intercalated titanium dichalcogenides in a wide range of copper concentrations (x = 0.04-0.8) using x-ray photoelectron spectroscopy, resonant photoelectron spectroscopy, and x-ray absorption spectroscopy has been performed. Shift towards low energies of the Ti 2p and Se 3d core level spectra and a corresponding decrease in the photon energy of Ti 2p absorption spectra with the increase in copper concentration have been found. These sign-anomalous shifts may be explained by the shielding effect of the corresponding atomic shells as a result of the dynamic charge transfer during the formation of a covalent chemical bond between the copper atoms and the TiSe2 matrix.
An experimental study of the electronic structure of VTiSe system in a wide range of vanadium concentrations (x = 0.06-0.9) using x-ray photoelectron spectroscopy and resonant photoelectron spectroscopy has been performed. The partial charge transfer from the VSe to TiSe structural fragments is experimentally observed, and the most part of the charge is localized on the vanadium atoms in the VSe structural fragments.
The comparison of the specifics of the guest-host chemical bonding in the materials with (Fe TiSe) and without (Fe TiTe) ordering of the iron atoms was performed. For this purpose the electronic structure of the materials were studied using X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, resonant X-ray photoelectron spectroscopy, and theoretical calculations (total density of states, partial density of states, and multiplet calculations). For the iron-intercalated TiTe compound iron-chalcogen bonds are formed, whereas the formation of iron-iron bonds is most typical for the iron-intercalated TiSe compound. This leads to an increase in the lifetime of electrons on the titanium atoms and does not allow the formation of atomic chains of intercalated metal.
The electronic structure of the NiTiSe intercalation compounds with disordered and ordered Ni atoms is studied using photoelectron, resonant photoelectron and X-ray absorption spectroscopy, theoretical calculations of the X-ray spectra and density of electronic states. The increase in the covalent component of the chemical bond of Ni and Ti with the nearest neighbour was found with increasing nickel concentration and its ordering. A significant charge transfer from the Ni atoms to the host lattice resulting in the transformation of Ti into Ti occurs, while the symmetry of the crystal lattice is lowered from the hexagonal to the monoclinic one.
The probability of charge transfer in layered titanium diselenide between monolayers containing Cr, Mn, and Cu with different concentrations and host lattice TiSe 2 is estimated according to the resonant photoemission data. For this purpose, the Raman-Auger contributions and narrow bands just below the Fermi energy were separated in the valence band spectra. These contributions provide the information about charge transfer. It is shown that the localization of the 3d electrons is typical for Cr and Cu atoms and strongly depends on theirs concentration. In Mn x TiSe 2 , Mn 3d electrons are delocalized and the probability of the charge transfer is the greatest as compared with other compounds under investigation. V C 2013 AIP Publishing LLC.
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