Zeolite Film Growth on Spin-Coated Silicon Wafers

Zeolites are nanoporous crystalline solids that find extensive use in catalysis, ion-exchange, and adsorption processes. New applications such as membranes, sensors, and low-k dielectric materials become possible when zeolites are cast into the form of thin films. Zeolites are grown from sol-gels that are heated at modest temperatures ranging from135-2000°C. Duration of heating times range from a few hours up to several weeks. The effects of aging the sol-gel solution for zeolite film growth has been extensively studied, but there is no consensus on what the optimal maturation time of the sol-gel is for a particular method of synthesis.  The goal of this study is to investigate zeolite (MFI phase) film growth as a function of the maturation age of the sol- gel solution. Particular film characteristics of interest include morphology, crystallinity, thickness, and relative orientation of the crystallites. MFI films were prepared by spin coating the precursor sol-gel of TEOS (tetraethyl orthosilicate), TPAOH (tetraproplyammonium hydroxide) and deionized H₂0 (in molar ratios of 1/0.20/40) onto silicon substrates. The substrates were placed in a Parr reactor held at a temperature of 180°C for 3 hours. The films were studied and characterized with X-ray diffraction and scanning electron microscopy. It is hypothesized  there is a positive correlation between aging time of sol-gel and crystal formation, i.e. larger crystals and more uniform films with preferred orientation.