Optical-luminescence yield spectra produced by x-ray excitation

Emura, S.; Moriga, Toshihiro; Takizawa, J; Nomura, Masaharu; Bauchspiess, Karl Rudolf; Murata, Takatoshi; Harada, Kiyomi; Maeda, Hironobu

doi:10.1103/physrevb.47.6918

Cited by 75 publications

(27 citation statements)

References 35 publications

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“…As is discussed below, this behaviour results from the combination of two effects: the secondary processes confinement and the change in X-ray penetration depth below and above the absorption edges of interest. [35] Briefly, the luminescence will originate from band gap excitonic emission through the recombination of electrons at the bottom of the conduction band and holes at the top of the valence band if there is no defects (electron and hole traps) or radiationless energy transfer; one will then observe mainly the near band gap emission. This is the case in the nanoneedle, which is a nearly perfect crystallite and most defects are of surface origin.…”

Section: Resultsmentioning

confidence: 99%

The Origin and Dynamics of Soft X‐Ray‐Excited Optical Luminescence of ZnO

et al. 2010

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The distinct optical emission from ZnO materials, nanoneedles and microcrystallites synthesized with different sizes and morphologies by a flow deposition technique, is investigated with X-ray excited optical luminescence (XEOL) and time-resolved X-ray excited optical luminescence (TR-XEOL) from a synchrotron light source at the O K and Zn L(3,2) edges. The innovative use of XEOL, allowing site-specific chemical information and luminescence information at the same time, is fundamental to provide direct evidence for the different behaviour and the crucial role of bulk and surface defects in the origin of ZnO optical emission, including dynamics. XEOL from highly crystalline ZnO nanoneedles is characterized by a sharp band-gap emission (~380 nm) and a broad red luminescence (~680 nm) related to surface defects. Luminescence from ZnO microcrystallites is mostly dominated by green emission (~510 nm) associated with defects in the core. TR-XEOL experiments show considerably faster decay dynamics in nanoneedles compared to microcrystallites for both band-gap emission and visible luminescence. Herein we make a fundamental step forward correlating for the first time the interplay of size, crystallinity, morphology and excitation energy with luminescence from ZnO materials.

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Section: Resultsmentioning

confidence: 99%

The Origin and Dynamics of Soft X‐Ray‐Excited Optical Luminescence of ZnO

et al. 2010

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“…We firstly consider why the oxygen OD-NEXAFS from the blue emission is positive, whereas the copper OD-NEXAFS from the red emission is negative. As considered theoretically by [28], and experimentally by many [13], positive-signal OD-XAS are expected when there is direct energy/electron transfer from the absorbing to the emitting species. For the processes considered here, this requires that the penetration depth of the X-rays is greater than the volume being excited.…”

Section: Optically Detected Xasmentioning

confidence: 98%

X‐ray absorption and luminescence properties of metallic copper nanoparticles embedded in a glass matrix

Roqué

Poolton

Molerà

et al. 2006

Physica Status Solidi (b)

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A new method of ion-exchange between raw compounds containing copper oxide and alkali glasses has been used to grow copper nanoparticles within a glass matrix, forming a metal-glass nanocomposite that is the structure on which both ancient and modern lustre glazes are based. When excited by X-rays at 300 K, two dominant emission bands appear in the material in the visible region, peaking at 2.60 eV and 1.98 eV. Synchrotron radiation methods are deployed that enables the luminescence and structural properties of the nanocomposite to be interlinked. Standard Extended X-ray Absorption Fine Structure (EXAFS) shows that both metallic copper and copper oxide local sites structure are present in the glass matrix, and the detailed atomic arrangement of each are derived; however, the method provides no information as to whether either structures are actually involved in the luminescence processes. In order to provide this direct link, Optically Detected X-ray Absorption Spectroscopy (OD-XAS) has been deployed, and this provides strong evidence that copper metal nanoparticles are responsible for the red emission. The method also shows that the X-ray absorption processes of the metal particles and silicate lattice (that result in the red and blue emissions respectively) are distinctly different. This is the first report of OD-XAS involving metallic nanoparticles, and opens the possibility of using the method more generally for metal nanoparticle research.

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“…In such cases, variation of the temperature can alter the charge percolation kinetics, and result in OD-XAS signatures becoming observable. Theoretical consideration for these thickness effects on OD-XAS spectra can be found in Goulon et al [8] and Emura et al [9]. Of relevance here, similar considerations apply to the concentration of atomic species in mixed/alloyed samples, where the effects of concentration and thickness are essentially equivalent.…”

Section: Background To the Od-xas Methodsmentioning

confidence: 92%

Application of wavelength‐resolved optically‐detected XAS methods to phase‐segregated silicates

Poolton¹,

Pantos²,

Hamilton³

et al. 2004

Physica Status Solidi (b)

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Wavelength-resolved optically-detected X-ray absorption experiments are described that monitor the emission from naturally occurring phase-exsolved aluminosilicate feldspars, when exciting across the Ca and K L 2,3 core levels. The results from a selection of example cases are presented that demonstrate the power of the technique in examining the structural and optical properties of phase segregated materials that could not easily be achievable by other methods. The results highlight that in these materials, extrinsic point defects such as Mn 2+ and Fe 3+ can also become preferentially associated with particular exsolved phases.

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Optical-luminescence yield spectra produced by x-ray excitation

Cited by 75 publications

References 35 publications

The Origin and Dynamics of Soft X‐Ray‐Excited Optical Luminescence of ZnO

The Origin and Dynamics of Soft X‐Ray‐Excited Optical Luminescence of ZnO

X‐ray absorption and luminescence properties of metallic copper nanoparticles embedded in a glass matrix

Application of wavelength‐resolved optically‐detected XAS methods to phase‐segregated silicates

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