1：Experimental Design and Method Selection:

The sol was prepared by magnetically stirring measured amounts of TEOS, H2O, and EtOH for 1 h. Then, speci?c quantities of HCl and dimethylacetamide were added as the catalyst and drying control agent and stirring was continued for further 5 h. The sol was aged at room temperature for a certain period of time to allow gel formation. This gel was then spin-coated at 1500 r min?1 20 times to form a liquid ?lm on a glass plate, which was hydrophilically treated with mixture of concentrated H2SO4:H2O2 = 1:

2：A uniform and dense SiO2 ?lm was prepared by heating the liquid ?lm after fumigation for 24 h in an atmosphere of saturated ammonia. In the heat treatment method, the ammonia treated ?lm was dried in a drying oven at 60 °C for 24 h, 80 °C for 24 h, and then placed it in a tube annealing furnace where the temperature was increased to 500 °C, based on the temperature curve under vacuum. Sample Selection and Data Sources:

The surface morphologies were studied under a metallographic microscope to determine the optimal parameters required for the preparation of SiO2 ?lm. The surface morphology and thickness of the crack-free ?lm was tested by scanning electron microscopy (SEM). The composition of the sample was analyzed by the X-ray photoelectron spectroscopy (XPS). The transmissivity of the sample was tested by UV–visible spectrophotometry. The crystal quality of the sample was analyzed by X-ray di?raction (XRD).

3：List of Experimental Equipment and Materials:

TEOS, H2O, EtOH, HCl, dimethylacetamide, glass plate, concentrated H2SO4, H2O2, ammonia, drying oven, tube annealing furnace, metallographic microscope, SEM, XPS, UV–visible spectrophotometer, XRD.

4：Experimental Procedures and Operational Workflow:

The sol was prepared by magnetically stirring measured amounts of TEOS, H2O, and EtOH for 1 h. Then, speci?c quantities of HCl and dimethylacetamide were added as the catalyst and drying control agent and stirring was continued for further 5 h. The sol was aged at room temperature for a certain period of time to allow gel formation. This gel was then spin-coated at 1500 r min?1 20 times to form a liquid ?lm on a glass plate, which was hydrophilically treated with mixture of concentrated H2SO4:H2O2 = 1:

5：A uniform and dense SiO2 ?lm was prepared by heating the liquid ?lm after fumigation for 24 h in an atmosphere of saturated ammonia. In the heat treatment method, the ammonia treated ?lm was dried in a drying oven at 60 °C for 24 h, 80 °C for 24 h, and then placed it in a tube annealing furnace where the temperature was increased to 500 °C, based on the temperature curve under vacuum. Data Analysis Methods:

The surface morphologies were studied under a metallographic microscope to determine the optimal parameters required for the preparation of SiO2 ?lm. The surface morphology and thickness of the crack-free ?lm was tested by scanning electron microscopy (SEM). The composition of the sample was analyzed by the X-ray photoelectron spectroscopy (XPS). The transmissivity of the sample was tested by UV–visible spectrophotometry. The crystal quality of the sample was analyzed by X-ray di?raction (XRD).