Epitaxial films stabilized by long-range forces

It has been widely accepted that the stability of an epitaxial film on a substrate of a different material is determined primarily by the competition between surface tension and stress. Here we propose that certain thermodynamic driving forces of different physical origins, acting over longer ranges than atomic length, can be strong enough to compete with elasticity. Specifically, we show that the ubiquitous dispersion force can compete effectively with the stress in thin solid films. We further show that the confined electrons within a metal film can mediate a surprisingly long-ranged force capable of stabilizing metal films of many atomic layers, leading to the existence of a thickness window within which smooth metal films can be formed.