Interlayer interaction in the conduction bands of layered transition-metal dichalcogenides studied by inverse photoemission

We have studied the dispersion of the unoccupied Ti 3d--derived conduction bands in 1T-TiSe₂ along the {Γ}A direction normal to the basal plane by measuring the photon spectra excited by normal-incidence electrons with kinetic energies between 10 and 20 eV. A triplet structure associated with two low-lying t2g-like d bands and a higher eg-like d band is clearly resolved within 3 eV above the Fermi level. The t2g bands show noticeable dispersion up to 0.4 eV from point {Γ} to point A resulting from interlayer interaction. No emission is observed related to empty Se 4p states at point {Γ} near the Fermi level. The results are critically compared with theoretical predictions and optical spectra.