ИСТИНА

Coupled diffusion-mechanical processes play a vital role in surface laser modification technologies. In this article, an analytical coupled diffusion-strain model for the dynamics of disorder carriers (atomic point defects) is proposed to study the effects of the surface elastic properties and the strain gradients on the instability of a laser-excited solid film with a nano-scale thickness. Dispersion relation of the diffusion-flexural instability (DFI) is obtained and analyzed. It is shown that the analysis, which simultaneously includes the surface elasticity, nonlocal second and fourth order strain gradient effects and normal and lateral defect–induced forces that cause the bending of surface layer, gives two maxima on the instability growth rate curve at a sufficiently far above the instability threshold. On the contrary, the growth rate has a single maximum if the instability threshold is slightly exceeded. The proposed model predicts the dependence of the nano-relief period on the film thickness, the properties of the energy source and material properties. The influence of atomic defect clustering due to DFI on the local or periodical exfoliation of deposited elastic layers on a substrate is also discussed.