Chemical trend of Fermi-level shift in transition metal-doped TiO2 films

Abstract

The effect of doping a wide range of transition metals (TMs) including V, Cr, Mn, Fe, Co, and Ni into rutile TiO 2 films grown on Nb-doped TiO 2 (110) single-crystal substrates was investigated by photoemission spectroscopy and X-ray absorption spectroscopy. For all TM-doped TiO 2 films, the Ti 2p and O 1s core levels were similarly shifted to lower binding energies with increasing film thickness and the shifts were similarly saturated at a film thickness of about 15 nm. These peak shifts could be interpreted in terms of the Fermi level shift, indicating that dopants trap excess electrons from the Ti 3d band like acceptors. The present systematic data revealed that the magnitude of the saturated Fermi level shift correlates well with the effective charge transfer energy.

Fullerene as a Photoelectron Transfer Promoter Enabling Stable TiO2‐Protected Sb2Se3 Photocathodes for Photo‐Electrochemical Water Splitting

“…[6] When photoelectrons are accumulated at the TiO 2 surface, however, the band edge of TiO 2 can be slipped up to achieve more negative potential than Φ red , followed by the reductive dissolution of TiO 2 from Adv. [37,38] Because the reductive dissolution of TiO 2 likely leaves surface defects, such as partially reduced Ti 4+ sites or oxygen vacancies, particularly at sub-surface regions, these defects can serve as trap states, impeding the transport of photogenerated electrons. 2019, 9,1900179 Only for PTS did the binding energy of the Ti 4+ state gradually shift to a lower level (dotted lines).…”

“…Therefore, it can be assumed that the surface of TiO 2 is photoreduced into the Ti(OH) 3 compound followed by its dissolution into the electrolyte rather than remaining at the surface (i.e., reductive dissolution takes place). On the other hand, the binding energy shift toward lower energies can be explained by the lowered fermi level of TiO 2 , typically observed when additional trap states form within the bandgap . Because the reductive dissolution of TiO 2 likely leaves surface defects, such as partially reduced Ti 4+ sites or oxygen vacancies, particularly at sub‐surface regions, these defects can serve as trap states, impeding the transport of photogenerated electrons .…”

Ab Initio Prediction of the Redox Potentials of 3d Transition Metals Embedded in a Semiconducting Host Lattice

“…These studies were completed by photocurrent and electron spin resonance (ESR) measurements few years later . Surprisingly, to our knowledge, only a few other experimental studies have been reported on the systematic characterization of TM doping in this material. − In parallel, plenty of first-principles insights have been collected on doped rutile TiO 2 . Formation energies and charge transition levels of intrinsic defects have been carefully detailed through the use of density functional theory. − ,, However, authors often did not consider extrinsic dopants.…”

First-row transition metal atoms adsorption on rutile TiO2(110) surface

“…Metal-doped TiO 2 materials have recently received a lot of attention [31][32][33]. In this perspective, we have considered two others interactions: (1) insertion when M is inserted between the two top-layers and (2) substitution/ insertion when M substitutes one surface penta-coordinated Ti that becomes inserted between the two top layers.…”