Heteroepitaxial growth modes revisited

Abstract

It is well known that the outcome of a thin film deposition experiment on a foreign substrate is determined by surface and interface energetics, which can be collected in one parameter, the change in surface energy, Ω. It is common knowledge that at equilibrium conditions, Ω < 0 leads to two-dimensional (2D) growth and Ω > 0 leads to the formation of three-dimensional (3D) islands. Using classical nucleation theory, we demonstrate the existence of an interval for the chemical potential difference during growth, where 2D nucleation is favorable for sufficiently small, but positive Ω. For larger Ω, 2D nucleation is suppressed in favor of 3D nucleation. We exemplify this for two cases where epitaxial growth is performed at low supersaturation: vapor–liquid–solid growth of nanowires, and liquid phase epitaxy. First, we explain why certain axial nanowire heterostructures can be grown straight in both interface directions. Second, we explain the formation of multilayer heterostructures in liquid phase epitaxy. Finally, we discuss Stranski–Krastanov growth in a low supersaturation limit and show that there is a thermodynamically defined critical thickness, which increases with the chemical potential difference.