Photoluminescence properties of MgO powders with coordinatively unsaturated surface ions

Anpo, Masakazu; Yamada, Yoshiaki; Kubokawa, Yutaka; Coluccia, Salvatore; Zecchina, Adriano; Che, Michel

doi:10.1039/f19888400751

Cited by 81 publications

(90 citation statements)

References 2 publications

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“…We have assigned this peak to the radiative recombination of electron-hole pairs excited by the incoming electrons across the band gap [28]. These excitonic modes are mobile in the bulk lattice but get trapped at low-coordinated surface sites, in particular at O corner and kink sites, where recombination takes place in a second step [29,30]. The 400-nm emission peak is therefore representative for exciton recombination at low-coordinated surface sites and can be quenched by dosing small amounts of metals, e.g., gold, onto the oxide film [31].…”

Section: A Experimental Resultsmentioning

confidence: 99%

Defect complexes in Li-doped MgO

et al. 2015

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Magnesium oxide (MgO) is used in a variety of industrial applications due to its low cost and structural stability. In heterogeneous catalysis, MgO and Li-doped MgO have been studied as catalysts for the oxidative coupling of methane. In this work, we analyze the structure and stability of defect complexes comprising Li dopants and oxygen vacancies in MgO, combining scanning tunneling microscopy, photon-emission experiments, and density-functional theory computations. The experimental results strongly indicate that after annealing Li-doped MgO to temperatures of 600 K and higher, Li evaporates from the surface, but Li defects, such as substitutional defects, interstitials, or defect complexes comprising Li remain in the bulk. Our calculations show that bulk defect complexes containing F 2+ color centers, that have donated their two electrons to two adjacent Li defects, are the most stable configurations at realistic pressure and temperature conditions.

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Section: A Experimental Resultsmentioning

confidence: 99%

Defect complexes in Li-doped MgO

et al. 2015

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“…131,132,133 Spatially-resolved optical experiments with an STM are therefore a powerful means to probe the defect structure of oxide surfaces. This is especially true, because structural parameters of the emission centre and its specific optical behavior can be explored simultaneously at the local scale.…”

Section: Photon Emission Spectroscopy With the Stmmentioning

confidence: 99%

“…As a result, surface steps, corners and kinks are the preferred trapping and recombination centers for coupled electron-hole pairs (excitons), being the fundamental electronic excitation in a gap material. 23,55,243 The decay of excitonic modes is the main source for the emission of photons 131,132,133 and hot-electrons from the oxide surface. 244,245,246 Not surprisingly, the properties and abundance of lowcoordinated surface sites is therefore tightly connected with the optical and photochemical activity of oxide materials.…”

Section: Defects In the Oxide Surfacementioning

confidence: 99%

“…Hereby, optical spectroscopy 131,132,133 , XPS and EELS 247,248 are ideally suited to detect defect-induced electronic states in the band gap, while electronparamagnetic resonance spectroscopy (EPR) is sensitive to oxide defects carrying an unpaired electron. 249 Thermal desorption and infrared-absorption spectroscopy, on the other hand, enable an investigation of defect-mediated adsorption processes.…”

Section: Defects In the Oxide Surfacementioning

confidence: 99%

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Properties of oxide thin films and their adsorption behavior studied by scanning tunneling microscopy and conductance spectroscopy

Nilius

2009

Surface Science Reports

221

233

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The preparation of thin oxide films on metal supports is a versatile approach to explore the properties of oxide materials that are otherwise inaccessible to most surface science techniques due to their insulating nature. Although substantial progress has been made in the characterization of oxide surfaces with spatially averaging techniques, a local view is often essential to provide comprehensive understanding of such systems. The scanning tunneling microscope (STM) is a powerful tool to obtain atomic-scale information on the growth behavior of oxide films, the resulting surface morphology and defect structure.

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“…However, they are usually unable to identify the spatial distribution and atomic position of defects in the surface. This information can only be accessed if a certain defect position imprints a characteristic electronic, 2 optical, 3 or magnetic signature 4 onto the averaging spectrum. The common way to map the spatial arrangement of defects in an oxide surface is the application of scanning probe techniques.…”

Section: Introductionmentioning

confidence: 99%

Probing the 4f states of ceria by tunneling spectroscopy

Shao

Jerratsch

Nilius

et al. 2011

Phys. Chem. Chem. Phys.

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Low-temperature scanning tunneling microscopy and spectroscopy have been employed to analyze the local electronic structure of the (111) surface of a ceria thin film grown on Ru(0001). On pristine, defect-free oxide terraces, the empty 4f states of Ce 4+ ions appear as the only spectral feature inside the 6 eV oxide band gap. In contrast, occupied states are detected between À1.0 and À1.5 eV below E Fermi in conductance spectra of different point and line defects, such as surface oxygen vacancies, grain boundaries and step edges. They are assigned to partially filled 4f states localized at the Ce 3+ ions. The presence of excess electrons indicates the oxygen-deficient nature of the direct oxide environment. The f state spectroscopy with the STM allows us to probe the spatial distribution of Ce 3+ ions in the ceria surface, providing unique insight into the local reduction state of this chemically important material system.

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Photoluminescence properties of MgO powders with coordinatively unsaturated surface ions

Cited by 81 publications

References 2 publications

Defect complexes in Li-doped MgO

Defect complexes in Li-doped MgO

Properties of oxide thin films and their adsorption behavior studied by scanning tunneling microscopy and conductance spectroscopy

Probing the 4f states of ceria by tunneling spectroscopy

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