Fracture of organosilicate glass thin films: environmental effects

Fracture of organosilicate glass coatings is shown to depend sensitively on reactive species in the environment: water vapor for fracture in ambient environments and hydroxyl ions for fracture in aqueous solutions. A simple model captures the key features of the experimental crack velocity curves, including the presence of a threshold energy release rate below which no crack propagation is observed and the effect of chemical species on crack velocity. The similarity between subcritical fracture of OSG in aqueous environments and results from a dissolution study suggests that both processes are controlled by the same mechanism. Bond densities obtained from both the ambient and the aqueous measurements are in line with expectations for organosilicate coatings. At high driving forces, crack growth in aqueous environments is limited by diffusion of hydroxyl ions to the crack tip.