Journal of Physics C: Solid State Physics

The experimental band structure of occupied and unoccupied states of titanium dichalcogenides

View publication


The authors have studied the dispersion of the electronic states of TiTe2 by combined angle-resolved inverse photo-emission (h(cross) omega =9.8eV) and photo-emission (h(cross) omega =21.2 eV) for various high-symmetry directions. The experimental band structure E(k/sub ///) is found to be in good agreement with a simple LCAO theory in particular for the unoccupied Ti3d-like bands. At Gamma they find a large trigonal splitting of 0.9 eV within the Ti3d-derived t2g states and observe additional photon emission associated with unoccupied Te 5p states. At the Brillouin zone boundary near M(L) emission due to the lowest d states is observed below and above EF for the same kp indicating possible many-body effects in the excitation process. This is attributed to the strong localisation of the Ti3d states at the Fermi level. Unoccupied Ti 4s, p-like bands that do not overlap the d states were detected 5-8 eV above the Fermi level. In the resulting bulk band gap between the d and s, p states they observed an image potential surface state 0.7 eV below the vacuum level. From its parabolic dispersion an effective mass m*=1.5 was determined. Similar results were obtained for the unoccupied states in TiSe3. © 1987 IOP Publishing Ltd.


22 Nov 2000


Journal of Physics C: Solid State Physics