Fig. 2

a Simulated image of the diffraction pattern. No strain was applied. The intensity is represented with colors. There is asymmetric behavior between the first-order diffraction spot on both sides of the zero-order beam because the screen in our simulation is set to be parallel to the grating instead of perpendicular to the reflection direction. b Simulated evolution of first-order diffraction spot under different biaxial strains. The intensity partial differential is represented with colors. The horizontal coordinate and vertical coordinate denote the position relative to the center of the zero-order diffraction spot. The peak is marked with a dashed line. From left to right, \({\varepsilon }_{x}\) was set as 0%, 0.9%, 2.6%, and 4.3%, respectively. From top to bottom, the \({\varepsilon }_{y}\) was 0%, 1%, 3%, and 5%, respectively