Fig. 3: Inversion symmetry broken and ferroelectricity of 3R-WS2 nanoflakes.
From: Reconfigurable and nonvolatile ferroelectric bulk photovoltaics based on 3R-WS2 for machine vision
a The angle dependence of SHG intensity of the 3R-WS2 nanoflake. b SHG spectra of 3R-WS2 nanoflake with different excitation powers. c The distribution diagram of SHG intensity exhibits a power-law relationship with excitation power, and the coefficient is fitted to 1.9. d Height image and OOP intrinsic amplitude images of 3R-WS2 nanoflake under different drive voltages. e Corresponding OOP amplitude evolution curve with different drive AC voltages. f OOP amplitude and phase images of 3R-WS2 after sequential lithography by using a box-in-box pattern. The inside of the white dotted line indicates −6 V, and the outside represents 6 V. g Local OOP ferroelectric switching spectra under DC off state of 3R-WS2 nanoflake.
