Observation of grain boundary plasmon and associated deconvolution techniques for low-loss electron energy-loss (EEL) spectra acquired from grain boundaries

Proloy Nandi; Eric R Hoglund; James M Howe

doi:10.1016/j.ultramic.2022.113478

Observation of grain boundary plasmon and associated deconvolution techniques for low-loss electron energy-loss (EEL) spectra acquired from grain boundaries

Ultramicroscopy. 2022 Apr:234:113478. doi: 10.1016/j.ultramic.2022.113478. Epub 2022 Jan 26.

Authors

Proloy Nandi¹, Eric R Hoglund², James M Howe³

Affiliations

¹ Department of Materials Science & Engineering, University of Virginia, Charlottesville, VA 22904, United States. Electronic address: pn2bb@virginia.edu.
² Department of Materials Science & Engineering, University of Virginia, Charlottesville, VA 22904, United States. Electronic address: erh3cq@virginia.edu.
³ Department of Materials Science & Engineering, University of Virginia, Charlottesville, VA 22904, United States. Electronic address: jh9s@virginia.edu.

PMID: 35158122
DOI: 10.1016/j.ultramic.2022.113478

Abstract

Spatially resolved valence electron energy-loss spectroscopy (VEELS) was used to acquire low-loss EEL spectra from Al grain boundaries (GBs) with different GB energies. The loss signal from the GB is highly delocalized and is mixed with the bulk loss, therefore requiring separation. Three different separation techniques, i.e., Fourier-log, Fourier-ratio deconvolution and direct subtraction, were employed to extract the GB response from the low-loss spectra and produced similar results. The GB response consists of a positive intensity peak from the excitation of GB plasmons (GBP) and a negative intensity begrenzungs (Bgs) peak from reduced scattering from bulk oscillations. Also, lower electron density at the GB reduces the inelastic scattering of the bulk plasmon. The intensity of GBP scattering and begrenzungs peak is found to increase toward the GBs, with maximum intensity when the electron probe is positioned on the GB, connecting the begrenzungs effect with the creation of a GBP.

Keywords: Begrenzungs (Bgs) peak; Bulk plasmon; Electron energy-loss spectroscopy (EELS); Fourier-log deconvolution; Fourier-ratio deconvolution; Grain boundary plasmon (GBP).