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, α and β, 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.