Evolution of surface waviness in thin films via volume and surface diffusion

Deformation mechanisms involving mass transport by stress driven diffusion influence a large number of technological problems. We study the formation of undulations on surfaces of stressed films at high temperature by exploring the deformation kinetics governed by volume and surface diffusion. A governing equation is derived that gives the amplitude change of such surfaces as a function of time. A parametric study is then carried out using a range of practically important input values of the film material properties. The results show that at the dominant instability wavelength, under low stress and high temperature conditions, the roughening is only caused by volume diffusion, while smoothing is only caused by surface diffusion. The results from the current model are compared to experimental observations reported in the literature for the roughening of metallic film surfaces under the low stress and high temperature conditions common in thermal barrier systems. ∗Corresponding author. Email: [email protected], Fax: 1(217) 244 5707.