Sol-Gel Thin Film Formation

Abstract

During sol-gel dip-coating, inorganic precursors are rapidly concentrated on the substrate surface by gravitational draining with concurrent evaporation and condensation reactions. We have presented examples of several factors that influence the structure of the deposited films: (1) size and opacity of fractal precursors; (2) relative rates of condensation and evaporation; (3) capillary pressure; (4) shear resulting from surface-tension-gradient-driven-flows; and (5) substrate withdrawal speed. By control of these factors it is possible to tailor the pore size, surface area, pore volume and refractive index of the deposited film for applications ranging from dense protective or passivation layers to films with precisely controlled pore sizes for sensor surfaces and separation membranes.