Fig. 1. Schematic diagram of an ALD reaction cycle
The silane precursor A reacts with hydroxyl groups on the surface of fused silica, and the inert gas purges excess precursors and by-products; then the oxidation precursor B reacts with the surface and purges again

Fig. 2. Thickness of ALD film versus growth cycle, the growth rate of SiO₂is about 0.1 nm·cycle^-1

Fig. 3. Deposition rate versus deposition temperature
In the experimental temperature range, the deposition rate increases with increasing temperature of substrate

Fig. 4. XRD of SiO₂ films deposited by ALD. The SiO₂ films are amorphous at different temperatures

Fig. 5. Sample surface roughness
(a): Fused silica substrate, 1.88 nm; (b): 275 ℃, 0.89 nm; (c): 300 ℃, 0.76 nm; (d): 325 ℃, 0.88 nm; (e): 350 ℃, 1.67 nm

Fig. 6. Ultraviolet-visible-near infrared transmission spectrum. SiO₂ films at different temperatures have no obvious effect on the spectral transmittance of the film

Fig. 7. Fourier transform infrared spectroscopy (FTIR)
(a): 400~1 500 cm^-1; (b): near 480 cm^-1; (c): near 780 cm^-1; (d): near 1 120 cm^-1; (e): 2 000~4 000 cm^-1

Fig. 8. (a) Fluorescence spectra curve and (b) peak fluorescence intensity of ALD films at different temperatures. SiO₂ films deposited at higher temperatures are closer to the characteristics of fused silica substrate

Fig. 9. (a) Damage probability curve and (b) zero probability damage threshold of ALD films at different temperatures. The damage performances after ALD coating are lower than that of the initial substrate