Comment on “Investigation on optical properties of ZnO nanowires by electron energy-loss spectroscopy”

Stöger-Pollach, Michael; Galek, T.

doi:10.1016/j.micron.2006.02.007

Cited by 8 publications

(3 citation statements)

References 7 publications

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“…For obtaining true electronic structure information from the low-loss spectra, a potential intensity contribution due to retardation radiation should be carefully regarded. [11][12][13] Retardation effects, such as the generation ofČerenkov radiation (ČR), could extend into the energy region near the bandgap. Hence, such contributions can modify the spectral features resulting in erroneous KKA.…”

Section: Resultsmentioning

confidence: 99%

Characterization of wurtzite ZnO using valence electron energy loss spectroscopy

et al. 2011

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The electronic structure of bulk wurtzite ZnO is investigated in valence electron energy loss spectroscopy with scanning transmission electron microscopy. To qualitatively interpret the characteristic spectral feature of ZnO, the complex dielectric function of ZnO is derived from the corresponding low-loss spectra. By scanning the electron probe across the sample from bulk toward the vacuum, four surface excitations intrinsic to ZnO can be identified. The surface plasmon of ZnO appearing around 16 eV is assigned, since with decreasing sample thickness, the volume plasmon is gradually replaced by this spectral feature. Moreover, with the excitation criterion of a negative real part (ε 1) of the dielectric constant of ZnO within this energy regime, the condition for surface plasmon is met. Surface exciton polaritons (SEPs) are found to appear at 9.5 and 13.5 eV, in which the relaxed condition for SEP excitation (ε 2 >ε 1 > 0) can be fulfilled, with rather weak excitonic oscillator strength (broad interband transitions). In addition, the guided light modes, which are excited by the retardation of incident electrons can be identified at 3.8 eV just above the ZnO bandgap, supported by a calculation employing the Kröger equation.

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Section: Resultsmentioning

confidence: 99%

Characterization of wurtzite ZnO using valence electron energy loss spectroscopy

et al. 2011

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“…Several excitation processes and features including plasmons, interband transitions, surface effects and relativistic losses have to be taken into account before an interpretation of the VEELS spectra can be made. [19][20][21][22] The dielectric response of nanomaterials can also be determined through discrete dipole approximation, boundary element or effective-medium theory (EMT) approaches. [23][24][25] The EMT is particularly interesting as it is widely used for a large variety of heterostuctures and it can also include local-field effects (LFE).…”

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confidence: 99%

“…44 This KKA approach however fails to take into account surface effects and Čerenkov losses as well as the intermixing, for anisotropic crystals, between the dielectric responses parallel and perpendicular to the electron beam. 22,45 Such effects can drastically hinder the determination of the dielectric properties. According to the dielectric function calculated in this paper, the acceleration voltage should be reduced below 40 kV to avoid any relativistic effects (leading to Čerenkov losses) in the low loss spectrum of α-MoO 3 .…”

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Strong anisotropic influence of local-field effects on the dielectric response ofα-MoO3

et al. 2013

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Dielectric properties of α-MoO 3 are investigated by a combination of valence electron-energy loss spectroscopy and ab initio calculation at the random phase approximation level with the inclusion of local-field effects (LFE). A meticulous comparison between experimental and calculated spectra is performed in order to interpret calculated dielectric properties. The dielectric function of MoO 3 has been obtained along the three axes and the importance of LFE has been shown. In particular, taking into account LFE is shown to be essential to describe properly the intensity and position of the Mo-N 2,3 edges as well as the low energy part of the spectrum. A detailed study of the energy-loss function in connection with the dielectric response function also shows that the strong anisotropy of the energyloss function of α-MoO 3 is driven by an anisotropic influence of LFE. These LFE significantly dampen a large peak in ε 2 , but only along the [010] direction. Thanks to a detailed analysis at specific k-points of the orbitals involved in this transition, the origin of this peak has not only been evidenced but a connection between the inhomogeneity of the electron density and the anisotropic influence of local-field effects has also been established. More specifically, this anisotropy is governed by a strongly inhomogeneous spatial distribution of the empty states. This depletion of the empty states is localized around the terminal oxygens and accentuates the electron inhomogeneity.

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Studies of Electronic Excitations of Rectangular ZnO Nanorods by Electron Energy-Loss Spectroscopy

Chu

Liu

et al. 2011

Plasmonics

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Comment on “Investigation on optical properties of ZnO nanowires by electron energy-loss spectroscopy”

Cited by 8 publications

References 7 publications

Characterization of wurtzite ZnO using valence electron energy loss spectroscopy

Characterization of wurtzite ZnO using valence electron energy loss spectroscopy

Strong anisotropic influence of local-field effects on the dielectric response ofα-MoO3

Studies of Electronic Excitations of Rectangular ZnO Nanorods by Electron Energy-Loss Spectroscopy

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