Fig. 1: Experimental setup and PSF structure.
From: Atomic-scale visualization of defect-induced localized vibrations in GaN
a Schematic of the experimental setup for phonon measurements. The electron beam is focused on the GaN sample with a PSF. The energy loss of the electron beam is analysed using an EELS spectrometer to determine the vibrational energy of the sample. b Schematic of the EELS aperture placement in reciprocal space. The green circle marks the on-axis geometry of the aperture with a 35 mrad convergence semiangle, and the yellow circle marks the position of the aperture with a 25 mrad collection semiangle. c Schematic of the experimental geometry, which shows the diffraction plane. The yellow rectangle illustrates the position of the slot aperture used in 4D-EELS. d HAADF-STEM image of the GaN PSF viewed along the [0001] zone axis. e GPA map of the PSF corresponding to the same area with (d), showing lattice strain component εxx.
