Characterization of wurtzite ZnO using valence electron energy loss spectroscopy

Michael R.S. Huang, Rolf Erni, Hsin Ying Lin, Ruey Chi Wang, Chuan Pu Liu

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

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 (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 (2> 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.

Original languageEnglish
Article number155203
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume84
Issue number15
DOIs
Publication statusPublished - 2011 Oct 17

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Electron energy loss spectroscopy
wurtzite
energy dissipation
electron energy
valence
spectroscopy
Excitons
polaritons
excitons
excitation
Electrons
electron probes
oscillator strengths
Electronic structure
Energy gap
Permittivity
Vacuum
permittivity
electronic structure
Transmission electron microscopy

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

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title = "Characterization of wurtzite ZnO using valence electron energy loss spectroscopy",
abstract = "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 (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 (2> 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 Kr{\"o}ger equation.",
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Characterization of wurtzite ZnO using valence electron energy loss spectroscopy. / Huang, Michael R.S.; Erni, Rolf; Lin, Hsin Ying; Wang, Ruey Chi; Liu, Chuan Pu.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 84, No. 15, 155203, 17.10.2011.

Research output: Contribution to journalArticle

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