Strong Metal–Sulfur Hybridization in the Conduction Band of the Quasi-One-Dimensional Transition-Metal Trichalcogenides: TiS₃ and ZrS₃

Abstract

The elemental contributions to the conduction bands of the transition-metal trichalcogenides TiS 3 and ZrS 3 were examined using X-ray absorption spectroscopy, at the Ti and S 2p edges and the Zr 3p edges. A comparative study of these two compounds shows that the bottom of the conduction band, for both TiS 3 and ZrS 3 , is comprised mainly of hybridized transition metal−sulfur orbitals, either Ti 3d and S 3p orbitals or Zr 4d and S 3p orbitals. Density functional theory and experiment both indicate that the bottom of the conduction band, in the case of TiS 3 , has the Ti 3d weight. Although weak, experiment indicates that the S-weighted contribution to the conduction band minimum for ZrS 3 is greater than in the case of TiS 3 . For ZrS 3 , theory, however, indicates that the conduction band is dominated by hybridization of the Zr 4d and S 3p orbitals, including in the vicinity of the bottom of the conduction band.

Electronic transport and polarization-dependent photoresponse in few-layered hafnium trisulfide (HfS3) nanoribbons

“…40 For HfS 3 , this strong S 3p -Hf 5d hybridization in the conduction band is far more extensive and extends well above the conduction band minimum to far higher energies than seen for either TiS 3 or ZrS 3 . 39 Besides explaining the transitions in the XAS spectra, the calculated band structure also shows the origin of the theoretical indirect band gap of about 1.6 eV (Fig. 8a), which agrees with the experimentally observed indirect band gap of 2.0 eV (Fig.…”

“…Theoretical calculation of band alignment using DFT carried out for monolayers of ZrS 3 , HfS 3 , and their heterostructures indicated that their valence band maximum is dominated by the p state of the chalcogen, whereas the conduction band minimum is dominated by the d state of the transition metal. 37 An in-depth study of TiS 3 and ZrS 3 by observing the unoccupied and occupied states above and below the Fermi level found through experiments and theory indicated that the unoccupied states of the conduction band are dominated by s–d or p–d hybridization, 39 consistent with previous predictions. 40 While there are photoemission studies of HfS 3 , 23 a systematic study of the unoccupied states of HfS 3 is absent and would be valuable for a better understanding of the optical excitation process.…”

“…The Fermi level ( E F ) has been placed at the base point of the absorption peak in a similar way as in the analysis of absorption edge spectra of TiS 3 and ZrS 3 . 39 The XAS S 2p core level spectrum (Fig. 7a) has been fit with four peaks, which we attribute to the Hf 5d contributions to the bottom of the conduction band.…”

“…38 X-ray absorption spectroscopy (XAS) provides a tool to probe the electronic bands contributing to the unoccupied density of states in trichalcogenides. 39 Fig. 7 shows the XAS spectra taken for the 2p core level edge of S and the 4d 5/2 edge of Hf.…”

“…40 While there are photoemission studies of HfS 3 , 23 a systematic study of the unoccupied states of HfS 3 is absent and would be valuable for a better understanding of the optical excitation process. 39…”