Effect of Adsorbed Donor and Acceptor Molecules on Electron Stimulated Desorption: O<sub>2</sub>/TiO<sub>2</sub>(110)

Zhang, Zhen; Yates, John T.

doi:10.1021/jz1007559

Cited by 75 publications

(118 citation statements)

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“…The band bending induced by the adsorbed (O2) − species is determined from core-level peak shifts in X-ray photoelectron spectroscopy (XPS). We discuss our results with respect to previous work on the prototypical rutile TiO2 (110) surface (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24).…”

mentioning

confidence: 55%

“…The adsorption of O2 has been studied in detail on the prototypical rutile (110) surface (11), and it is well accepted that an electron transfer is a prerequisite for O2 chemisorption. This was first proved by integral techniques, mainly a combination of TPD, photodesorption, and electron-stimulated desorption (12,(14)(15)(16)(17)(18)(19). The excess electrons on the rutile (110) surface are mainly provided by surface oxygen vacancies (22,23,44), although subsurface Ti interstitials also play a role (21).…”

Section: Discussionmentioning

confidence: 99%

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Electron transfer between anatase TiO ₂ and an O ₂ molecule directly observed by atomic force microscopy

Setvín

Hulva

Parkinson

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Activation of molecular oxygen is a key step in converting fuels into energy, but there is precious little experimental insight into how the process proceeds at the atomic scale. Here, we show that a combined atomic force microscopy/scanning tunneling microscopy (AFM/STM) experiment can both distinguish neutral O molecules in the triplet state from negatively charged (O) radicals and charge and discharge the molecules at will. By measuring the chemical forces above the different species adsorbed on an anatase TiO surface, we show that the tip-generated (O) radicals are identical to those created when () an O molecule accepts an electron from a near-surface dopant or () when a photo-generated electron is transferred following irradiation of the anatase sample with UV light. Kelvin probe spectroscopy measurements indicate that electron transfer between the TiO and the adsorbed molecules is governed by competition between electron affinity of the physisorbed (triplet) O and band bending induced by the (O) radicals. Temperature-programmed desorption and X-ray photoelectron spectroscopy data provide information about thermal stability of the species, and confirm the chemical identification inferred from AFM/STM.

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mentioning

confidence: 55%

Section: Discussionmentioning

confidence: 99%

Electron transfer between anatase TiO ₂ and an O ₂ molecule directly observed by atomic force microscopy

Setvín

Hulva

Parkinson

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…As shown in Figure 1.1, a charged metal plate was hypothesized to induce charges in the semiconducting material and therefore increase the conductivity. 11 This scheme, however, did not work [12][13] and a model was proposed by John Bardeen to explain the independence of the work function to the position of the Fermi level in the bulk of the semiconductor. 14 Surface states were proposed to exist at the free surface of the semiconductor and these states could be charged in the absence of an external field or metal contact.…”

Section: Statesmentioning

confidence: 99%

Measurement of the Band Bending and Surface Dipole at Chemically Functionalized Si(111)/Vacuum Interfaces

2013

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The core-level energy shifts observed using X-ray photoelectron spectroscopy (XPS) have been used to determine the band bending at Si(111) surfaces terminated with Si–Br, Si–H, and Si–CH3 groups, respectively. The surface termination influenced the band bending, with the Si 2p3/2 binding energy affected more by the surface chemistry than by the dopant type. The highest binding energies were measured on Si(111)–Br (whose Fermi level was positioned near the conduction band at the surface), followed by Si(111)–H, followed by Si(111)–CH3 (whose Fermi level was positioned near midgap at the surface). Si(111)–CH3 surfaces exposed to Br2(g) yielded the lowest binding energies, with the Fermi level positioned between midgap and the valence band. The Fermi level position of Br2(g)-exposed Si(111)–CH3 was consistent with the presence of negatively charged bromine-containing ions on such surfaces. The binding energies of all of the species detected on the surface (C, O, Br) shifted with the band bending, illustrating the importance of isolating the effects of band bending when measuring chemical shifts on semiconductor surfaces. The influence of band bending was confirmed by surface photovoltage (SPV) measurements, which showed that the core levels shifted toward their flat-band values upon illumination. Where applicable, the contribution from the X-ray source to the SPV was isolated and quantified. Work functions were measured by ultraviolet photoelectron spectroscopy (UPS), allowing for calculation of the sign and magnitude of the surface dipole in such systems. The values of the surface dipoles were in good agreement with previous measurements as well as with electronegativity considerations. The binding energies of the adventitious carbon signals were affected by band bending as well as by the surface dipole. A model of band bending in which charged surface states are located exterior to the surface dipole is consistent with the XPS and UPS behavior of the chemically functionalized Si(111) surfaces investigated herein.

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“…11,16 The behavior of O 2 chemisorbed on TiO 2 (110) is also well studied. 5,7,11,[16][17][18][19][20][21][22] It has been found, both experimentally 5,7,11,[16][17][18][19][20][21] and theoretically, 22 that the electronic desorption of O 2 , originally adsorbed on BBO oxygen vacancy defect sites, is caused by holes produced either by UV excitation or by holes produced by 100 eV electron impact. The production of holes in TiO 2 may be accurately monitored by measuring the yield of desorbing O 2 molecules.…”

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confidence: 99%

Electron-Mediated CO Oxidation on the TiO₂(110) Surface during Electronic Excitation

Zhang

Yates

2010

J. Am. Chem. Soc.

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The role of electrons and holes in the electronically excited oxidation of adsorbed CO on TiO(2)(110) has been investigated by tuning the surface electron and hole availability by the adsorption of Cl(2) or O(2). The presence of an electron acceptor (Cl(2) or O(2)) on the TiO(2)(110) surface causes upward band bending, increasing the excited hole availability and decreasing the excited electron availability in the near surface region. This enhances O(2) desorption and depresses CO(2) production during electronic excitation. This result gives clear evidence for the first time that the electronically excited CO oxidation reaction is caused by an electron-mediated process in contrast to O(2) desorption which is mediated by holes.

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Effect of Adsorbed Donor and Acceptor Molecules on Electron Stimulated Desorption: O₂/TiO₂(110)

Cited by 75 publications

References 31 publications

Electron transfer between anatase TiO ₂ and an O ₂ molecule directly observed by atomic force microscopy

Electron transfer between anatase TiO ₂ and an O ₂ molecule directly observed by atomic force microscopy

Measurement of the Band Bending and Surface Dipole at Chemically Functionalized Si(111)/Vacuum Interfaces

Electron-Mediated CO Oxidation on the TiO₂(110) Surface during Electronic Excitation

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Effect of Adsorbed Donor and Acceptor Molecules on Electron Stimulated Desorption: O2/TiO2(110)

Cited by 75 publications

References 31 publications

Electron transfer between anatase TiO 2 and an O 2 molecule directly observed by atomic force microscopy

Electron transfer between anatase TiO 2 and an O 2 molecule directly observed by atomic force microscopy

Measurement of the Band Bending and Surface Dipole at Chemically Functionalized Si(111)/Vacuum Interfaces

Electron-Mediated CO Oxidation on the TiO2(110) Surface during Electronic Excitation

Contact Info

Product

Resources

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Effect of Adsorbed Donor and Acceptor Molecules on Electron Stimulated Desorption: O₂/TiO₂(110)

Electron transfer between anatase TiO ₂ and an O ₂ molecule directly observed by atomic force microscopy

Electron transfer between anatase TiO ₂ and an O ₂ molecule directly observed by atomic force microscopy

Electron-Mediated CO Oxidation on the TiO₂(110) Surface during Electronic Excitation