High resolution EELS using monochromator and high performance spectrometer: comparison of V2O5 ELNES with NEXAFS and band structure calculations

Su, Dang Sheng; Zandbergen, H.W.; Tiemeijer, Peter; Kothleitner, Gerald; Hävecker, Michael; Hébert, C.; Knop‐Gericke, Axel; Freitag, Bert; Hofer, Ferdinand; Schlögl, Robert

doi:10.1016/s0968-4328(03)00033-7

Cited by 46 publications

(37 citation statements)

References 7 publications

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“…For example, EEL spectra of single crystal V 2 O 5 that were acquired with a monochromated energy resolution of 0.22 eV show additional shoulders in the vanadium L 2,3 peaks (at ~515 eV) compared with non-monochromated spectra taken with 85 0.6 eV resolution. 26 XAS measurements of the V 2 O 5 crystal were also acquired with a spectral resolution of 0.08 eV. The shoulders observed in the monochromated EEL spectra were clearly resolved as peaks by XAS, but the improved energy resolution did not reveal any further structures in the V L 2,3 edge.…”

Section: Spectral Resolutionmentioning

confidence: 99%

Correlative electron and X-ray microscopy: probing chemistry and bonding with high spatial resolution

et al. 2015

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Two powerful and complementary techniques for chemical characterisation of nanoscale systems are electron energy-loss spectroscopy in the scanning transmission electron microscope, and X-ray absorption spectroscopy in the scanning transmission X-ray microscope. A correlative approach to spectromicroscopy may not only bridge the gaps in spatial and spectral resolution which exist between the two instruments, but also offer unique opportunities for nanoscale characterisation. This review will discuss 10 the similarities of the two spectroscopy techniques and the state of the art for each microscope. Case studies have been selected to illustrate the benefits and limitations of correlative electron and X-ray microscopy techniques. In situ techniques and radiation damage are also discussed. IntroductionGrowth in the development and applications of nanotechnology 15 brings with it an increasing need for characterisation methods capable of providing both structural and chemical analysis on the nanometre scale. Most laboratory based characterisation techniques such as ultra-violet and infra-red spectroscopies, mass spectrometry and thermogravimetric analysis provide spatially 20 averaged information from comparatively large volumes of sample. While these techniques provide a representative overview of the sample, their averaged signals often probe not only the nanomaterial of interest, but also any support material, debris and impurities in heterogeneous structures. In addition, averaged 25 properties miss statistical outliers, which may be critical for the function of the nanomaterial. For characterisation of interfaces or individual nanostructures, techniques with much higher spatial resolutions are essential.There are few available techniques capable of providing 30 chemical information on the nanometre scale. This review will discuss two such methods: electron energy-loss spectroscopy in the scanning transmission electron microscope (STEM-EELS) and X-ray absorption spectroscopy in the scanning transmission X-ray microscope (STXM-XAS). These spectroscopies study the 35 primary processes of inelastic electron scattering or X-ray absorption to obtain chemical information, from chemical speciation analysis to local bonding environments and electronic structure. While the secondary process of X-ray emission also provides chemical information in the electron and X-ray 40 microscopes (by energy dispersive X-ray spectroscopy and X-ray probe X-ray micro-and nano-analysis respectively), these techniques, whilst being very sensitive to low concentrations, are limited to elemental analysis, and they will not be discussed in this review. Although the probe-specimen interactions of EELS 45 and XAS differ (electron scattering and photon absorption, respectively), they provide remarkably similar chemical information. Due to recent advances in diffractive optics for soft (100 eV to 2 keV 1 ) X-rays, as well as monochromators and aberration correctors for electron microscopes, the spatial and 50 spectral resolutions of STXM-XAS...

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Section: Spectral Resolutionmentioning

confidence: 99%

Correlative electron and X-ray microscopy: probing chemistry and bonding with high spatial resolution

et al. 2015

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“…Vacancies in vanadium oxide have been probed using a variety of spectroscopic techniques, such as scanning tunneling microscopy, 9,26,27 electron energy loss spectroscopy, 28,29 electron paramagnetic resonance studies, 16,12,23 X-ray absorption measurements, 30 and X-ray photoemission spectroscopy (XPS). 15,17 However, most of these techniques either require ultrahigh vacuum (UHV) or controlled environment for operation that makes it difficult to adapt it to 6 in-situ catalytic studies.…”

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confidence: 99%

Defect-induced Burstein-Moss shift in reduced V2O5 nanostructures

et al. 2016

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The main effects of oxygen vacancy defects on the electronic and optical properties of V 2 O 5 nanowires were studied through in-situ Raman, photoluminescence, absorption, and photoemission spectroscopy. Both thermal reduction and electrochemical reduction via lithium insertion leads to the creation of oxygen vacancy defects in the crystal that gives rise to new electronic mid-gap defect states at energy 0.75 eV below the conduction band edge. The defect formation results in delocalization and injection of excess electrons into the conduction band, as opposed to localized electron injection as previously suggested. Contrary to what is seen in most oxides, the presence of vacancy defects leads to band filling and an increase in the optical band gap of V 2 O 5 from 1.95 eV to 2.45 eV, which is attributed to the Burstein-Moss effect. Other observed changes in the optical properties are correlated to the changes in the electronic structure of the oxide as result of defect formation. Further, in-situ Raman measurements during the electrochemical reduction at room temperature show that the oxygen atom that is most readily reduced is the three-fold coordinated oxygen (O3). Reduction of V 2 O 5 through the formation of oxygen vacancy, V O , defects have been studied both by theoretical and experimental studies. 10,11,12,13,14,15 In this work, we address some of the key unanswered questions regarding the correlation between optical properties and electronic structure of The rise of absorbance in the NIR spectral range in reduced oxide is a result of optical excitation of V O defect related mid-gap states. In addition, using in-situ Raman measurements during reduction process, we show that the oxygen atom that most readily participates during electrochemical reduction at room-temperature and gets reduced is the three-fold coordinated oxygen (O3).Vacancies in vanadium oxide have been probed using a variety of spectroscopic techniques, such as scanning tunneling microscopy, 9,26,27 electron energy loss spectroscopy, 28,29 electron paramagnetic resonance studies, 16,12,23 X-ray absorption measurements, 30 and X-ray photoemission spectroscopy (XPS). 15,17 However, most of these techniques either require ultrahigh vacuum (UHV) or controlled environment for operation that makes it difficult to adapt it to 6 in-situ catalytic studies. Here, we use near-infrared photoluminescence (NIR-PL) and Raman spectroscopy that allows for study of vacancy defects and their interaction with redox species under in-operando electrochemical conditions at room temperature, as shown in our recent study. 31 The spectral range of various types of electronic transitions in V 2 O 5 is shown in Fig.1A.Representative PL spectra of stoichiometric and non-stoichiometric V 2 O 5 are shown in Fig.1B.The optical gap of nominally undoped V 2 O 5 is in the range of 1.9-2.5 eV and hence emission spectrum lies in the ultraviolet-to-visible part of the spectral range. In most TMOs, deviation from stoichiometry is a result of the presence of high density ...

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“…transition and noble metals, oxides including transition metal oxides and sulfides). Su et al [46] studied the near-edge fine structures of the V L 2,3 and O K edges of V 2 O 5 which exhibits a complicated fine structure at the V L 3 edge consisting of six overlapping peaks. Even with a total energy resolution of 0.22 eV, the obtained ELNES is nearly comparable with XANES data of 0.08 eV energy resolution which means that better energy resolution does not further improve the information content at least in this case.…”

Section: Core-loss Eelsmentioning

confidence: 99%

An Introduction to High-resolution EELS in Transmission Electron Microscopy

et al. 2008

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The practical advantages of an electron monochromator for electron energy-loss spectroscopy (EELS) in transmission electron microscopy are described. Typical examples from materials and nanoparticle research demonstrate the use of EELS with high energy and spatial resolution. Recent instrumental developments are also reviewed with a discussion of how the technique could be used to study catalyst structures of the future.

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High resolution EELS using monochromator and high performance spectrometer: comparison of V2O5 ELNES with NEXAFS and band structure calculations

Cited by 46 publications

References 7 publications

Correlative electron and X-ray microscopy: probing chemistry and bonding with high spatial resolution

Correlative electron and X-ray microscopy: probing chemistry and bonding with high spatial resolution

Defect-induced Burstein-Moss shift in reduced V2O5 nanostructures

An Introduction to High-resolution EELS in Transmission Electron Microscopy

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