Abstract
Current generation electron monochromators employed as attachments to scanning transmission electron microscopes (STEM) offer the ability to obtain vibrational information from materials using electron energy-loss spectroscopy (EELS). We show here that in crystals, long-and short-wavelength phonon modes can be probed simultaneously with on-axis vibrational STEM EELS. The long-wavelength phonons are probed via dipole scattering, while the short-wavelength modes are probed via impact scattering of the incident electrons. The localized character of the short-wavelength modes is demonstrated by scanning the electron beam across the edge of a hexagonal boron nitride nanoparticle. It is found that employing convergence angles that encompass multiple Brillouin zone boundaries enhances the short-wavelength phonon contribution to the vibrational energy-loss spectrum much more than that achieved by employing collection angles that encompass multiple Brillouin zone boundaries. Probing short-wavelength phonons at high spatial resolution with on-axis vibrational STEM EELS will help develop a fundamental connection between vibrational excitations and bonding arrangements at atomic-scale heterogeneities in materials.
Original language | English (US) |
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Pages (from-to) | 1069-1077 |
Number of pages | 9 |
Journal | Microscopy and Microanalysis |
Volume | 27 |
Issue number | 5 |
DOIs | |
State | Published - Oct 1 2021 |
Keywords
- Brillouin zone boundary
- impact
- localized
- phonon
- short wavelength
- vibrational EELS
ASJC Scopus subject areas
- Instrumentation