Thin film coatings are used extensively for such diverse applications as protective and optical coatings, passivation and planarization layers, sensors, high or low dielectric constant films, inorganic membranes, electro-optic and nonlinear optical films, electrochromic, semiconducting anti-static coatings and ferroelectric films.

      The sol-gel process offers a low-temperature method for synthesizing materials that are either totally inorganic in nature or both inorganic and organic. The process, which is based on the hydrolysis and condensation reaction of organometallic compounds in alcoholic solutions, offers many advantages for the fabrication of coatings, including excellent control of the stoichiometry of precursor solutions, ease of compositional modifications, customizable microstructure, ease of introducing various functional groups or encapsulating sensing elements, relatively low annealing temperatures, and simple and inexpensive equipment.

      The sol-gel process uses inorganic or metal organic precursors. The most commonly used alkoxide is dissolved in alcohol and hydrolyzed by the addition of water under acidic, neutral or basic conditions, although film formation is also possible by the deposition of alkoxide solutions followed by exposure to moisture. Hydrolysis replaces an alkoxide ligand with a hydroxyl ligand, as shown in the equation:

M(OR)z + H2O -> M(OR)z-1(OH) + ROH

      Condensation reactions involving the hydroxyl ligands produce polymers composed of M-O-M bonds as shown in the following equations, for silicon condensation:

Si(OR)3OH + Si(OR)4 -> (RO)3Si-O-Si(OR)3 + ROH
2Si(OR)3OH -> (RO)3Si-O-Si(OR)3 + H2O
Further reactions lead to the formation of silicon oxides.

      Chemical precursors play a key role in the sol-gel coating by directly affecting the porosity, refractive index, hardness and other performance characteristics of the resultant coatings and thin films. Chemat has developed a stable family of chemical precursors—Polymeric Metal Oxoalkoxides for sol-gel coating applications.

      Numerous special solutions have been formulated in Chemat for impart special functionalities to the substrate. These coating solutions are ready to use. The resultant coatings possess the desired functionality such as hydrophobic nature, scratch resistance, and antireflection.