Fig. 8: The influence of share strain.

A MoS₂ flake (indicated by ball and stick model) is under a uniaxial tensile loading in (a). The blue arrows represent the loading direction and σ is the stress in this loading condition. The black solid line with arrow indicates the [010] crystal direction. The resulting principle strains ε₁ and ε₂ are depicted by the blue dashed arrows around the unit body in (b), where the black solid arrows represent the crystal coordinate system. Then the strain state is transformed into the crystal coordinate system, where normal strains ε_xx and ε_yy, shear strain γ_xy (γ_yx) are indicated by the dashed arrows around the unit body in (c). Normalized PISs under this loading condition is displayed in (d), with the three sets of petals named as P1, P2, P3. Dots are detected experimental results and lines are fitted values. The obtained PISs are under the loading strain ε_xx of 0.12% (black), 0.25% (red), 0.38% (blue) and 0.5% (green), respectively. In (e), the black square points and red round points represent the experimental results of petal amplitude ratios η₁ and η₂, respectively. Black and red solid lines represent the theoretical values of η₁ and η₂, respectively. R₁² and R₂² are the R-Square values for the correlations between experimental data and theoretical results.