Observation and model of highly ordered wavy cracks due to coupling of in-plane stress and interface debonding in silica thin films

Highly ordered wavy cracks are observed in silica films deposited on crystalline Si wafer. The wavy crack path is interpreted in terms of the coupling of the in-plane film crack and the interface debonding. A model based on the analyzing of the crack path and the stress evolution is proposed to describe the propagation of the wavy cracks. A scaling relationship between the wavelength (lambda) and amplitude (A) is found (lambda similar to A(xi)) and the scaling factor is determined to be xi=0.47 +/- 0.01.