Analysis Of Epitaxial Morphology Evolution Under Stress And Diffusion Mechanisms

The macroscopic properties of the thin-film material depend on microstructure evolution during the epitaxial growth. there is an extremely close relationship between microstructure properties and atomic behaviors on the substrate surface. Consequently, it is of great significance to probe a series of atomic processes such as surface diffusion,nucleation,growth and the interaction between atoms,coalescence, instability,degeneration and so forth.In this paper, a new phase-field model based on diffusion interface is put forward to describe the epitaxial growth of island nucleation,growth and ripening. This model includes combined effects of elastic field,surface energy, deposition, diffusion, desorption and energy barrier. We use classical BCF model to describe the atoms diffusion and nucleation process, and use a new free energy function that including elastic strain energy to obtain a phase-field equation can describe the growth of dynamic multi-island boundaries by variation. This method can effectively simulates the complex epitaxial morphology of epitaxial growth. Solve the nonlinear coupled equations by finite difference scheme.The numerical result show that, our model can reproduce the real multilayer epitaxial growth structure, the simulation results are consistent with experimenta results.This paper also simulates the complex growth stress with morphology evolution. Results show that, accompanied with the epitaxial growth, complex stress distribution was produced, and the stress reaches a local maximum on the boundaries of the island, which consisten with the experimental results.The last bu most important, the stress significantly affects the atom diffusion process. When stress exists, the epitaxial structure changes faster.We also use the phase-field model to simulate the step growth and surface annealing process, the morphology evolution is consistent with experimental results. and the stairs instability phenomena machine rational inquiry. Conclusions were as follows: step meandering is always in the the state of dynamic evolution under the competitive effect between Gibbs-Thomson effect and KES barriers. During deposition, KES effect plays a dominant role, leading step meandering coexist with step bunching. When interrupt deposition and during the annealing process, Gibbs-Thomson effect plays a dominant role, steps become smooth gradually.