Electronic and Crystal Structure of New CrxZrSe2 Intercalation Compounds.

New intercalation compounds CrxZrSe2 were synthesized and thoroughly studied. Cr atoms were found to occupy the positions both tetrahedrally and octahedrally coordinated by the Se atoms in the interlayer gap. The magnetic properties and electrical resistivity were studied in the temperature ranges of 2.4-300 K and 80-340 K, respectively. The compounds change their behavior from semiconducting (x = 0.1) to metallic (x > 0.1). The magnetic interaction strongly depends on the Cr content and temperature. The spin-glass state with antiferromagnetic interaction exists at T < Tcrit for CrxZrSe2 with x ≤ 0.2, while at x ≥ 0.3 ferromagnetic contribution arises as well. The single crystals of CrxZrSe2 were grown to study the electronic structure of the materials. A combination of the X-ray photoelectron spectroscopy (including that across Cr 2p-3d and Zr 3p-4d resonance) and X-ray absorption spectroscopy methods allowed to propose the location of the Cr 3d-states in the Se 3p-Zr 4d energy gap.

Effect of the Titanium Self-Intercalation on the Electronic Structure of TiSe2.

The effect of the superstoichiometric Ti intercalation on the electronic structure of TiSe2 was studied by using X-ray photoelectron spectroscopy in nonresonant and resonant modes along with the DOS (density of states) calculations. It was shown that the presence of the Ti atoms in the interlayer space leads to the formation of the Ti 3dz2/Ti 3dz2 hybridized band between the Ti atoms in the regular lattice positions and Ti atoms in the interlayer space. The charge transfer to the conduction band was not observed in this case.

Electronic Structures of the Vanadium-Intercalated and Substitutionally Doped Transition-Metal Dichalcogenides TixVySe2.

The electronic structures of V-intercalated TiSe2 and substitutionally doped dichalcogenides Ti1-xVxSe2 have been studied using soft X-ray photoelectron, resonant photoelectron, and absorption spectroscopies. In the case of the substitution of Ti by V, the formation of coherently oriented structural fragments VSe2 and TiSe2 is observed and a small charge transfer between these fragments is found. Intercalation of the V atoms into TiSe2 leads to charge transfer from the V atoms to the Ti atoms with the formation of covalent complexes Ti-Se3-V-Se3-Ti.

Guest-Host Chemical Bonding and Possibility of Ordering of Intercalated Metals in Transition-Metal Dichalcogenides.

The comparison of the specifics of the guest-host chemical bonding in the materials with (Fe xTiSe2) and without (Fe xTiTe2) 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 TiTe2 compound iron-chalcogen bonds are formed, whereas the formation of iron-iron bonds is most typical for the iron-intercalated TiSe2 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.