Importance of surface oxygen vacancies for ultrafast hot carrier relaxation and transport in 
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O

Ricca, Chiara; Grad, Lisa; Hengsberger, Matthias; Osterwalder, Jürg

doi:10.1103/physrevresearch.3.043219

Cited by 13 publications

(10 citation statements)

References 43 publications

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“… 33 , 34 , 36 , 37 The underlying decay channels were assigned by density functional theory (DFT) to in-gap resonances at 1.6 and 1.5 eV above the VB top, introduced by V O2+ and V O+ defects, respectively. 38 While V O2+ centers preferentially develop in highly p-type oxides with the VB top pinned to E F , as in our case, any downshift of the VB promotes the formation of single-charged V O+ defects. Our detected STM luminescence deviates markedly from this V O emission response, as it covers a much wider wavelength range from 700 to 950 nm and depends sensitively on the actual tip state.…”

supporting

confidence: 60%

“…The PL signature of V O2+ and V O+ complexes in Cu 2 O are peaks at 750 and 850 nm, broadened to 80–100 nm FWHM due to finite sample crystallinity. ,,, The underlying decay channels were assigned by density functional theory (DFT) to in-gap resonances at 1.6 and 1.5 eV above the VB top, introduced by V O2+ and V O+ defects, respectively . While V O2+ centers preferentially develop in highly p-type oxides with the VB top pinned to E F , as in our case, any downshift of the VB promotes the formation of single-charged V O+ defects.…”

mentioning

confidence: 53%

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Light Emission from Single Oxygen Vacancies in Cu₂O Films Probed with Scanning Tunneling Microscopy

Gloystein

Soltanmohammadi

Nilius

2023

J. Phys. Chem. Lett.

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Global photoluminescence (PL) and spatially resolved scanning tunneling microscopy (STM) luminescence are compared for thick Cu 2 O films grown on Au(111). While the PL data reveal two peaks at 750 and 850 nm, assigned to radiative electron decays via localized gap states induced by O vacancies, a wide-band emission between 700 and 950 nm is observed in STM luminescence. The latter is compatible with cavity plasmons stimulated by inelastic electron tunneling and contains no spectral signature of the Cu 2 O defects. The STM luminescence is nonetheless controlled by O vacancies that provide inelastic excitation channels for the cavity plasmons. In fact, the emission yield sharply peaks at 2.2 V sample bias, when tip electrons are resonantly injected into O defect states and recombine with holes at the valence-band top via plasmon stimulation. The spatially confined emission centers detected in photon maps of the Cu 2 O films are therefore assigned to excitation channels mediated by single or few O vacancies in the oxide matrix.

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confidence: 60%

mentioning

confidence: 53%

Light Emission from Single Oxygen Vacancies in Cu₂O Films Probed with Scanning Tunneling Microscopy

Gloystein

Soltanmohammadi

Nilius

2023

J. Phys. Chem. Lett.

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“…Prior to CO 2 adsorption, the two excess electrons at the oxygen vacancy occupy states which are resonant with the valence band of Cu 2 O and create an empty localized defect state about 1.6 eV above the valence band maximum. 28 Upon adsorption, the CO 2 accepts one of the two excess electrons from the oxygen vacancy as a result of the hybridization between CO 2 and the Cu 2 O surfaces, as evidenced by the broadened orbitals in Figure 4. This excess electron is transferred to the lowest unoccupied molecular orbital (LUMO) of CO 2 , destabilizing the C−O bond.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The corresponding excited-state reaction energy profiles are then investigated, as shown in Figures C, C, and C. Prior to CO 2 adsorption, the two excess electrons at the oxygen vacancy occupy states which are resonant with the valence band of Cu 2 O and create an empty localized defect state about 1.6 eV above the valence band maximum . Upon adsorption, the CO 2 accepts one of the two excess electrons from the oxygen vacancy as a result of the hybridization between CO 2 and the Cu 2 O surfaces, as evidenced by the broadened orbitals in Figure .…”

Section: Resultsmentioning

confidence: 99%

Plasmonic Energetic Electrons Drive CO₂ Reduction on Defective Cu₂O

Salavati-fard

Wang

2023

ACS Catal.

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Plasmonic photoreduction of CO 2 is valuable for decarbonization and producing valueadded chemicals. However, insights into the mechanisms of this reaction remain elusive, particularly regarding the roles of structural defects and their interplay with the nonequilibrium charge carriers. Here, we report density functional theory calculations on Cu 2 O, a prototype photocatalyst, through which we investigate CO 2 reduction over three defected facets to reveal the interfacial charge transfer and bond dynamics under plasmonic excitation. We find that the activation barrier of C−O bond cleavage decreases from 3.2 to about 1 eV, assisted by oxygen vacancies, and that the remaining barrier can be further reduced or eliminated at the plasmon-excited states when Cu 2 O is integrated with plasmonic metals. The regeneration of oxygen vacancies (by H 2 to form water) on Cu 2 O to complete the catalysis cycle is feasible and not affected by the energetic electrons. Our calculations thus show the important synergistic effect of energetic electrons and point defects to promote CO 2 reduction.

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“…All calculations were performed using the DFT periodic Vienna ab initio Simulation Package (VASP) [33]. Since conventional DFT functionals cannot provide a good description of the strong correlation effect between partially filled 3d Cu states in CuO [34], DFT +U calculations were performed using the Perdew-Burke-Ernzerhof (PBE) density functional and the Projected Augmented Wave method (PAW) while the plane wave cutoff energy was set at 500 eV [35].…”

Section: Computational Detailsmentioning

confidence: 99%

First-principles investigation of CuO decomposition and its transformation into Cu2O

Jabraoui

Rouhani

Rossi

et al. 2022

Phys. Rev. Materials

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This paper reports on the mechanisms of CuO decomposition and its associated phase transformation into Cu2O, as a fundamental step of thermite materials reaction, where CuO serves as the oxidizer. Frenkel pair defects in perfect bulk CuO show extremely high formation energy (>4 eV) indicating that its decomposition initiates at defects/interfaces/surfaces, the latter being sensitive to surface orientation. In contrast to a variety of CuO surfaces ((111), ( 110), (101 ̅ )) exhibiting three-fold coordinated oxygen atoms, results show that oxygen vacancy formation requires higher disordered surfaces, such as the CuO(001), on which the vacancy formation activation energy is reduced to 1.31 eV. This leads to the exothermic formation of a chemisorbed O-O peroxy-bridge complex at the surface (-1.25 eV adsorption), that thermodynamically moderates the backreaction (vacancy annihilation). Further desorption of molecular oxygen necessitates an activation of 1.53 eV, compatible with CuO decomposition observed experimentally at 600 K (~second process duration). As a driving mechanism of oxygen release upon decomposition, migrations of the vacancy close to the surface and towards the bulk are determined for a number of crystalline directions and surface orientations and

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Importance of surface oxygen vacancies for ultrafast hot carrier relaxation and transport in Cu2 O

Cited by 13 publications

References 43 publications

Light Emission from Single Oxygen Vacancies in Cu₂O Films Probed with Scanning Tunneling Microscopy

Light Emission from Single Oxygen Vacancies in Cu₂O Films Probed with Scanning Tunneling Microscopy

Plasmonic Energetic Electrons Drive CO₂ Reduction on Defective Cu₂O

First-principles investigation of CuO decomposition and its transformation into Cu2O

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Importance of surface oxygen vacancies for ultrafast hot carrier relaxation and transport in Cu2 O

Cited by 13 publications

References 43 publications

Light Emission from Single Oxygen Vacancies in Cu2O Films Probed with Scanning Tunneling Microscopy

Light Emission from Single Oxygen Vacancies in Cu2O Films Probed with Scanning Tunneling Microscopy

Plasmonic Energetic Electrons Drive CO2 Reduction on Defective Cu2O

First-principles investigation of CuO decomposition and its transformation into Cu2O

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Light Emission from Single Oxygen Vacancies in Cu₂O Films Probed with Scanning Tunneling Microscopy

Light Emission from Single Oxygen Vacancies in Cu₂O Films Probed with Scanning Tunneling Microscopy

Plasmonic Energetic Electrons Drive CO₂ Reduction on Defective Cu₂O