Observation of a growth instability during low temperature molecular beam epitaxy

The growth of a Cu(100) crystal has been investigated with helium atom beam scattering in real time and examined in the light of the dynamical scaling hypothesis. The associated exponents have been determined. The analysis of both terrace and step correlations during growth provides a detailed scenario of how a singular surface can transform into an arrangement of vicinal surfaces upon unstable growth, resulting in a pyramidlike surface profile. The sides of these pyramids are composed of the (113) and (115) Cu surface for deposition at 160 and 200 K, respectively.