Change of kinetic roughening with surfactant hydrogen in Ge on Si(001) system

The growth mode of Ge on a Si(001) substrate can be modified in the presence of dynamically supplied atomic hydrogen as a surfactant. A transition from the 3D to 2D growth was observed in scanning tunneling microscope images as the hydrogen flux increased to 1ML/sec. A layer-by-layer growth was successfully achieved with the hydrogen surfactant up to 8 monolayers of Ge. This growth behavior can be explained by kinetic roughening theory, showing a scaling behavior. The growth and roughness exponents, alpha and beta, seem to decrease with hydrogen. It is believed that hydrogen saturates the dangling bonds and limits diffusion of the incoming Ge, resulting in a formation of large two dimensional islands.