TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The depositing step involves spin-coating, roller-coating, or spray-coating. The curing comprises involves exposing the coating layer to ultraviolet (UV) radiation for curing for 5-120 seconds. The low-index coating has thickness of 500-4000 Angstrom after firing in the oven; and refractive index of less than 1.32 (preferably less than 1.28, especially less than 1.25) at 550 nm. The substrate comprises glass or silicon wafer. The method (M1) additionally involves depositing a high index coating on the substrate prior to the step of depositing the silica precursor on the substrate. Preferred Components: The silica sol does comprises silane which comprises (3-glycidoxypropyl)trimethoxysilane. The silica precursor additionally comprises an antifoaming additive, and solvent comprising an alcohol. The amount of the photoinitiator in the radiation curable composition is 0.1-10 wt.%; and the amount of silicon dioxide in the silica precursor is 0.1-10 wt.%.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The radiation curable composition comprises UV-curable epoxy, UV-curable acrylate, and/or UV-curable isocyanate. EXAMPLE - A mixture comprising Cyracure UVR-6107 (RTM: UV curable epoxy monomer) (96 g), and Cyracure UVI-6992 (RTM: cationic photoinitiator) (4 g) was prepared. To the mixture (15.65 g), (3-glycidoxypropyl)trimethoxysilane (GLYMO) (0.5 g), and 0.7 g of 70% dispersion colloidal silica in methylethyl ketone, were added to form stable silica precursor formulation. The resulting viscous formulation was particularly suitable for roller coating process to produce coatings on large substrates. This coating formulation was applied within minutes after preparation to soda lime glass substrates by spin coating method to produce coatings of varying thickness. Coatings were cured at room temperature by exposure to UV radiation for 30-40 seconds, and then fired at 625 degrees C for 5 minutes to form silica coating. At 2000 revolutions per minutes, thickness of the coating after UV curing was found to be 8.9 micron, whereas thickness of the coating after firing at 625 degrees C for 5 minutes was found to be 3550 Angstrom .