Example Buckling of an oxide film

Oxide films of different thicknesses were thermally grown at a temperature of 1200 °C on a relatively thick metal alloy substrate. Upon cooling to room temperature (20 °C), the oxide films were found to develop a large equi-biaxial residual compressive stress, primarily as a consequence of its thermal contraction mismatch with the substrate. The elastic modulus and Poisson ratio for the film are Ef = 400 GPa and = 0.25, respectively, at room temperature, and the coefficients of thermal expansion for the film and the substrate are af = 8 X 10 °C and (Us = 14 X 10 respectively. 

For h = 5 pm, the width of the smallest interface delamination at the edge of the film which would buckle under the influence of the compressive mismatch stress in the film is found from (5.8) to be Om = 45.6 m. 

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