Fig. 1. Reflectance spectrum designed for Cr+Al+MgF₂ samples

Fig. 2. Reflectance at central wavelength of 121.6 nm for LaF₃/MgF₂ samples under different designs. (a) Different film stacks; (b) different thickness ratios of H to L

Fig. 3. Measured reflectance spectra of Al+MgF₂ samples under different conditions. (a) Different deposition processes; (b) different annealing temperatures

Fig. 4. Roughness of different Al+MgF₂ samples. (a) Sample A; (b) sample B; (c) sample C

Fig. 5. Reflectance comparison of LaF₃/MgF₂ samples prepared at room temperature

Fig. 6. Reflectance of LaF₃/MgF₂ samples prepared at room temperature under different annealing processes

Fig. 7. Roughness of LaF₃/MgF₂ samples prepared at room temperature. (a) No annealing; (b) annealing-200 ℃/2 h; (c) annealing-250 ℃/2 h; (d) annealing-300 ℃/2 h

Fig. 8. Surfaces of LaF₃/MgF₂ samples prepared at room temperature. (a) No annealing; (b) annealing-200 ℃/2 h; (c) annealing-250 ℃/2 h; (d) annealing-300 ℃/2 h