Determination of the Modulus of Thin Sol-Gel films Using Buckling Instability

Buckling instabilities have been used to estimate the elastic modulus of thin sot gel films. The sot gel films (65-400 nm) were coated on elastomeric supports, which were then subjected to a compressive strain imposed directly or as a result of thermal stresses generated during the curing cycle. Atomic force and optical microscopies were used to characterize the buckling wavelength, and electron microscopy was used to estimate the thickness of the films. Elastic modulus was calculated using the classical buckling theory. This procedure, which was demonstrated previously by others starting with the systematic studies of Stafford et al. (Nature Mater. 2004, 3, 545-550), proves to be an effective way of determining the elastic modulus of thin films. The technique is used to study the effects of the concentration of the chemical precursors, curing temperature, and the duration of cure and humidity on the moduli of sol gel films, which provide valuable information about its performance when used as an adhesion promoter.