The critical layer number of epitaxially grown Cu and Ni films with strained structure

The thickness dependent structural transition of epitaxially grown thin films from a tetragonal structure to the corresponding bulk structure is thermodynamically considered. It is found that there exists a competition between elastic energy of the tetragonal structure and film–substrate interface energy. Equilibrium between these energies is present at a critical layer number nc. The predictions for nc are in agreement with the experimental results of some different metallic films deposited on fcc metallic substrates