Atomistic simulation of stress evolution during island growth

We report the results of a series of hybrid molecular dynamics simulations of the growth of islands on a substrate for several different island/substrate interface energies. When the interface energy is small, the islands tend to be thin and broad and the magnitude of the compressive stress–thickness product is relatively large. As the interface energy increases, the islands become taller and thinner and the magnitude of the compressive stress–thickness product decreases. This trend is consistent with experimental observations. The island aspect ratio dependence on interface energy follows from consideration of the equilibrium wetting angle. The effect of interface energy on the stress–thickness product shows that the island shape, surface/interface stresses and island stresses are self-equilibrated. A simple theory is developed that shows that the stress–thickness product is simply proportional to the substrate coverage and the substrate surface stress. The present simulations yield a simple, accurate, validated theory for stress development during the pre-coalescence stage of film growth.