Fig. 1. Schematic diagram of the working principle of the microwave cyclotron resonance ion source

Fig. 2. Ridge structure impurity target

Fig. 3. AFM topography and Fourier transform of sapphire sputtered by Ar⁺ ion beam with or without impurities

Fig. 4. PSD curve graph of Ar⁺ ion beam sputtering sapphire surface with or without impurity assistance（U_beam=1000 eV,

Fig. 5. Schematic diagram of island structure formation process

Fig. 6. AFM image and Fourier transform of the sapphire sample surface after etching with different incident energ（α_ion=65°,J_ion=487 μA/cm²,T=60 min）

Fig. 7. PSD curves and trends of height and RMS of nanostructures on the surface of sapphire samples after etching with different incident energy (α_ion=65°,J_ion=487 μA/cm²,T=60 min)

Fig. 8. Surface topography of sapphire sample etched with 1200 eV energy