Vacant states of TiO₂ with rutile structure and their reflection in different‐type x‐ray absorption spectra

Abstract

A tight‐binding linearized muffin‐tin orbital method was applied for the calculation of the densities of states (DOS) for TiO2 with the rutile structure in the wide energy region of the conduction band. The calculated partial DOS of titanium and oxygen were compared with the experimental Ti 2p total electron yield spectrum (TEY), which was measured in the present work, and the Ti 1s x‐ray absorption spectrum, O 1s TEY and bremstrahlung isochromat spectrum taken from the literature. We found that in the energy region higher than ∼6 eV above the bottom of the conduction band the fine structure of experimental absorption spectra follows the distribution of the corresponding partial DOS. In connection with this, one does not need to use any satellite mechanism for an interpretation of these spectra. In the region of vacant Ti 3d states (up to ∼6 eV), correspondence between the experimental and calculated splitting of t2g and eg subbands is observed in all spectra except Ti 2p TEY. As we showed using atomic calculations, this is connected with the Ti 2p53d1 multiplet in the final state of absorption which leads to suppression of the intensity of lower states of the t2g subband in Ti 2p TEY of TiO2. As a result, t2g–eg splitting extracted from Ti 2p3/2 and Ti 2p1/2 TEY is less than in Ti 3d DOS and other experimental spectra (Ti 1s XAS and O 1s TEY) in which an interaction of core level vacancy with photoelectron is absent owing to the delocalized character of valent states. Copyright © 2002 John Wiley & Sons, Ltd.

X-ray spectroscopic study of the electronic structure of visible-light responsive N-, C- and S-doped TiO2

“…26,55 The peaks in the Ti 2p 3/2 XPS spectra in orbitals. 31 The Ti 2p XAS of TiO 2-x N x is very similar to that of pure rutile TiO 2. This suggests that the influence of the N dopant on the TiO 2 structure and crystal field is very small.…”

“…For TiO 2 , the lowenergy range of the spectra (528-535 eV) was dominated by two strong broad bands, attributed to the oxygen 2p states hybridized with the empty split Ti 3d bands. 27,28,31 The high-energy part of the spectrum was formed by the delocalized antibonding O 2p states coupled with Ti 4sp band with principally O 2p character. 28 The origin for the bands C-E was the same as analyzed above in the Ti XAS spectra.…”

“…The electronic structure of TiO 2 is well understood both theoretically and experimentally, [27][28][29][30][31][32][33][34][35][36][37][38] and is characterized by a band gap located between the oxygen 2p valence band and the titanium 3d conduction band. 27 X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) are powerful element-specific probes of the electronic structure of materials, and have been applied extensively to study pure TiO 2 .…”

“…27 X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) are powerful element-specific probes of the electronic structure of materials, and have been applied extensively to study pure TiO 2 . [16][17][18][19][20][21]24,[27][28][29][30][31][32][33][34][35][36][37][38][39] In XAS, a core-level electron absorbs an x-ray photon and is excited to an unoccupied state above E F . 15,17,27,38 In XES, a valence band electron relaxes to a core hole created by the x-ray absorption process via the emission of an x-ray photon.…”

Exploring the incorporation of nitrogen in titanium and its influence on the electrochemical corrosion resistance in acidic media

“…The peaks between 537 eV and 550 eV are due to the delocalized antibonding O 2p states coupled to Ti 4sp with principally O 2p character. The origin for the σ* bands are related to the Ti 2p, 4s and 4p states hybridized with the O 2p orbitals [36]. The pristine film features the same spectrum after the electrochemical test indicating that the sample remains oxidized with its TiO 2 nature (figure 7b2).…”