Oxygen 1<i>s</i>x-ray absorption of tetravalent titanium oxides: A comparison with single-particle calculations

Groot, Frank M. F. de; Faber, J.; Michiels, J. J. M.; Czyżyk, M. T.; Abbate, M.; Fuggle, J. C.

doi:10.1103/physrevb.48.2074

Cited by 277 publications

(198 citation statements)

References 30 publications

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“…Figure 4(a) shows O 1s XAS of STO:Nb and STO. The O 1s XAS line shape of STO is in good agreement with that reported by de Groot et al [28]. The overall line shape except for the sharpness of the peak at hν ∼ 533.2 eV as indicated by a square in Fig.…”

supporting

confidence: 80%

“…4(a) was well reproduced by the oxygen-p-projected unoccupied density of states of STO calculated using a local-density approximation [28]. The sharp peak at hν ∼ 533.2 eV appearing in the excitation region of O 1s → O 2p states hybridized into Ti 3d e g states was attributed to the O 1s core hole in the XAS final state [28]: the electron excited into the e g band is strongly influenced by the O 1s core-hole potential through large Ti 3d e g -O 2p hybridization to form a core-excitonic state. The peak at hν ∼ 533.2 eV is supressed and broadened in the spectrum of STO:Nb [ Fig.…”

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confidence: 78%

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Coherent and Incoherent Excitations of Electron-DopedSrTiO3

et al. 2008

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Resonant photoemission at the Ti 2p and O 1s edges on a Nb-doped SrTiO3 thin film revealed that the coherent state (CS) at the Fermi level (EF) had mainly Ti 3d character whereas the incoherent in-gap state (IGS) positioned ∼1.5 eV below EF had mixed character of Ti 3d and O 2p states. This indicates that the IGS is formed by a spectral-weight transfer from the CS and subsequent spectral-weight redistribution through d-p hybridization. We discuss the evolution of the excitation spectrum with 3d band filling and rationalize the IGS through a mechanism similar to that proposed by Haldane and Anderson. PACS numbers:SrTiO 3 (STO) is a perovskite-type oxide semiconductor with a band gap of 3.2 eV [1] and is considered to be one of the promising device materials in "oxide electronics." A variety of transition-metal oxides can be grown on STO with atomical flatness to show novel phenomena such as the high-mobility and magnetic interface of

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confidence: 80%

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confidence: 78%

Coherent and Incoherent Excitations of Electron-DopedSrTiO3

et al. 2008

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“…The observed spectral broadening could stem from more itinerant electrons [35][36] and/or structural distortion 37 of the electrode material under delithiated states. We note that a direct measurement of the electronic conductivity of a cycled Li1-xNi0.5Mn1.5O4 material is non-trivial due to the existence of the conductive carbon.…”

Section: Results Andmentioning

confidence: 99%

Direct Experimental Probe of the Ni(II)/Ni(III)/Ni(IV) Redox Evolution in LiNi_0.5Mn_1.5O₄ Electrodes

et al. 2015

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KEYWORDS: high voltage spinel, LiNi0.5Mn1.5O4, Ni(III), soft x-ray spectroscopy.2 ABSTRACT LiNi0.5Mn1.5O4 spinel is an appealing cathode material for next generation rechargeable Li-ion batteries due to its high operating voltage of ~4.7 V (vs. Li/Li + ). Although it is widely believed that the full range electrochemical cycling involves the redox of Ni(II)/(IV), it has not been experimentally clarified whether Ni(III) exists as the intermediate state, or a double-electron transfer takes place. Here, combined with theoretical calculations, we show unambiguous spectroscopic evidence of the Ni(III) state when the LiNi0.5Mn1.5O4 electrode is half charged.This provides a direct verification of single-electron-transfer reactions in LiNi0.5Mn1.5O4 upon cycling, namely, from Ni(II) to Ni(III), then to Ni(IV). Additionally, by virtue of its surface sensitivity, soft x-ray absorption spectroscopy also reveals the electrochemically inactive Ni 2+and Mn 2+ phases on the electrode surface. Our work provides the long-awaited clarification of the single-electron transfer mechanism in LiNi0.5Mn1.5O4 electrodes. Furthermore, the experimental results serve as a benchmark for further spectroscopic characterizations of Nibased battery electrodes.3

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“…38 Comparison of the STO Ti 4+ -only spectrum in Figure 1 In contrast, the O K edge features may be divided into two regions: two low-energy peaks at 530 eV and 532.5 eV that show strong hybridization between O 2p and Ti 3d states, and a broader region between 536-548 eV exhibiting mixing of Ti 4sp and O 2p states. 36 The lower-energy peaks for the various samples resemble the spectrum from the target material due to similar Ti-O hybridization with the intensity for the two peaks for the fresh samples equal in magnitude and insensitive to film thickness from 15 nm to 87 nm on STO. Since these lower-energy peaks are sensitive to neighboring Ti ions, one would expect similar spectra between the edge-sharing TiO 6 octahedra in LTO and the distorted edge-sharing octahedra in ramsdellite Li 2 Ti 3 O 7 and rutile TiO 2 when compared to the corner-sharing octahedra in STO.…”

Section: Ti L 23 and O K X-ray Absorption Spectroscopymentioning

confidence: 99%