Fig. 2: On-axis and off-axis EELS measurements of buckled 2D GaN.

a Schematic diagram of the on-axis and off-axis geometries used in this study. b EELS line profile of buckled 2D GaN at on-axis geometry. The detecting area is marked by the green dashed box in Fig. 1d. Each layer is separated with black dashed lines. The line profile is obtained by integrating the EELS map in the detecting area. The position where the EELS spectra of buckled 2D GaN in (c) are extracted is marked by an orange triangle. c EELS spectra of bulk and buckled 2D GaN at on-axis geometry. The signals were extracted from Fig. S6b and (b). d EELS line profile of buckled 2D GaN at off-axis geometry. The detecting area is the same as that in (b). Each layer is separated with black dashed lines. The position where the EELS spectra of buckled 2D GaN in (e) are extracted is marked by an orange triangle. e EELS spectra of bulk and buckled 2D GaN at off-axis geometry. The signals were extracted from Fig. S6d and (d). The intensities are in log scale.