Surface X-Ray Scattering during Crystal Growth: Ge on Ge(111)

The growth of Ge on Ge(111) has been monitored by in situ x-ray reflectivity and diffraction. For suitably chosen geometries, the scattered x-ray intensity is extremely sensitive to atomic-scale surface morphology; dramatic intensity changes occur upon deposition of a fraction of a monolayer. For substrate temperatures up to 200^∘{}C oscillations are observed in the scattered intensity, indicating growth by two-dimensional nucleation. Reflectivity curves reveal the detailed surface atomic geometry. All observations can be quantitatively understood by use of kinematical diffraction theory.