Surface modification of multilayer FePS₃ by Ga ion irradiation

In order to investigate the modification of the surface structure of FePS₃ via Ga⁺ ion irradiation, we study the effect of thickness and Raman spectrum of multilayer FePS₃ irradiated for 0 μs, 30 μs, and 40 μs, respectively. The results demonstrate that the intensity ratio of characteristic Raman peaks are obviously related to the thickness of FePS₃. After Ga⁺ ion irradiation, the FePS₃ sample gradually became thinner and the E_u peak and Eg(v₁₁) peak in the Raman spectrum disappeared and the peak intensity ratio of A_1g(v₂) with respect to A_1g(v₁) weakened. This trend becomes more apparent while increasing irradiation time. The phenomenon is attributed to the damage of bipyramid structure of [P₂S₆]^4- units and the cleavage of the P-P bands and the P-S bands during Ga⁺ ion irradiation. The results are of great significance for improving the two-dimensional characteristics of FePS₃ by Ga⁺ ion beam, including structural and optical properties, which pave the way of surface engineering to improve the performance of various two-dimensional layered materials via ion beam irradiation.