Control of three-dimensional island growth with mechanically responsive single-crystal nanomembrane substrates.

Freestanding, ultracompliant crystalline-sheet substrates provide a new opportunity to control the growth of strained epitaxial films. Three-dimensional SiGe islands grown on thin silicon nanomembranes self-order as the strain field induced by initial island growth guides nucleation of subsequent islands on the opposite surface. A mechanics analysis explains this unique growth mode, possible only on ultracompliant substrates. The ordering can be tailored by manipulating the thickness and elastic properties of the membrane.