Publications Details
Fundamentals of sol-gel film deposition
Results appear to confirm the concept of surfactant-templating of thin film mesostructures. Final film pore structure depends on starting surfactant and water concentrations and process time scale (governed by evaporation rate). Surfactant ordering at substrate-film and film-vapor interfaces orients the porosity of adjoining films, leading to graded structures. SAW experiments show that depending on processing conditions, the porosity may be open or closed (restricted). Open porosity is monosized. Upon pyrolysis, lamellar structures collapse, while the hexagonal structures persist; when both hexagonal and lamellar structures are present, the hexagonal may serve to pillar the lamellar, avoiding its complete collapse. Thick lamellar films can be prepared because the surfactant mechanically decouples stress development in adjoining layers. Upon drying and heating, each individual layer can shrink due to continuing condensation reactions without accumulating stress. During surfactant pyrolysis, the layers coalesce to form a thick crack-free layer. Formation of closed porosity films is discussed.