Strain in ultrathin epitaxial films of Ge/Si(100) measured by ion scattering and channeling

We describe a channeling analysis of the strain associated with ultrathin (2-6 monolayers) epitaxial films of Ge embedded in Si. Measured strains are at the level of 3-4%, exceeding that accessible in bulk materials. These values, in both single-layer films and Ge-Si superlattices, are in approximate agreement with bulk elastic properties suggesting that Poisson's ratio is applicable at the few-monolayer level.