Fig. 2: HAADF-STEM images and SHG signals of γ-GaSe.
From: Emergence of ferroelectricity in a nonferroelectric monolayer
a, b The planar-view HAADF-STEM image and corresponding SAED pattern of γ-GaSe along the [001] zone axis, respectively. c, d The cross-section HAADF-STEM image and corresponding SAED pattern of γ-GaSe along the [100] zone axis, respectively. e SHG spectra generation from γ-GaSe nanoflake with different excitation powers. Inset: the SHG intensity exhibits a power-law relationship with excitation power, and the coefficient is fitted to 2.06. f Polarization angle \(\theta\) dependent SHG intensity. The red line is the fitted curve of the scattered experimental data.
