Fig. 4: Phonon dispersions of bulk GaN and buckled 2D GaN extracted using 4D-EELS. | Nature Communications

Fig. 4: Phonon dispersions of bulk GaN and buckled 2D GaN extracted using 4D-EELS.

From: Phonon dispersion of buckled two-dimensional GaN

Fig. 4

a Schematic of the EELS slot aperture displacement used in the experimental setup of 4D-EELS. The bright spots show the diffraction pattern of the sample at the \([11\bar{2}0]\) zone axis. The brightest spot is the transmission spot. The green rectangle marks the slot aperture, which corresponds to the momentum path \(\Gamma -{{\rm M}}\). b Phonon dispersion of bulk GaN extracted using 4D-EELS. The calculated phonon dispersion of bulk GaN is indicated by white lines. c 4D-EELS simulation results for bulk GaN, based on the calculated phonon dispersion in Fig. 3b. The calculated phonon dispersion of bulk GaN is also indicated by white lines. d Calculated phonon dispersion projected onto the buckled 2D GaN. This is the sum of the squared norms of the vibration eigenvectors from the upper and lower layers of the buckled 2D GaN, corresponding to the cyan and yellow channels in Fig. 3f. e Phonon dispersion of the buckled 2D GaN extracted using 4D-EELS. f 4D-EELS simulation results for buckled 2D GaN, based on the calculated phonon dispersion in Fig. 3f.

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