Optical properties of freestanding GaN nanomembranes using monochromated valence-EELS

Optical properties of freestanding GaN nanomembranes using monochromated valence-EELS

[Display omitted] •The dielectric function of freestanding GaN nanomembranes is studied.•The dielectric function is described with the help of monochromated valence EELS.•Optical characteristics n, k, α and R are numerically deduced. In the present study, the dielectric function of freestanding GaN...

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Bibliographic Details
Published in:Materials science & engineering. B, Solid-state materials for advanced technology Vol. 272; p. 115333
Main Authors: Benaissa, M., Sigle, W., Benabdallah, I., ElAfandy, R.T., Ng, T.K., van Aken, P.A.
Format: Journal Article
Language:English
Published: Lausanne Elsevier B.V 01-10-2021
Elsevier BV
Subjects:
Absorptivity
Critical point
Density functional theory
Dielectric function
Electron energy loss spectroscopy
Electron probes
Energy dissipation
GaN
Microscopes
Monochromated TEM
Nanomembrane
Optical properties
Refractivity
Valence EELS
Dielectric function
Valence EELS
Nanomembrane
GaN
Monochromated TEM
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Summary:[Display omitted] •The dielectric function of freestanding GaN nanomembranes is studied.•The dielectric function is described with the help of monochromated valence EELS.•Optical characteristics n, k, α and R are numerically deduced. In the present study, the dielectric function of freestanding GaN nanomembranes was described using valence electron energy loss spectroscopy coupled to a monochromated electron probe in a Sub-Electron-volt Sub-Angstrom transmission electron Microscope. Such a technique has proven to be very efficient in handling nanometer-scale freestanding nanomembranes and provided local and direct measurements of optical characteristics. Indeed, core-state along with outer-shell electrons transitions were first measured in the configuration where the GaN c→-axis was normal to the transferred momentum q→. With the help of Kramers-Kroning analyses and density functional theory, critical points energies were extracted and assigned. Finally, optical data such as the real refractive index n, extinction coefficient k, absorption coefficient α and reflectivity R were numerically deduced from the real and imaginary parts of the dielectric function.
ISSN:0921-5107
1873-4944
DOI:10.1016/j.mseb.2021.115333