Kinetic Growth Manipulation during Molecular Beam Epitaxy

The growth of ultra thin films of Cu and Ni on Cu(111) as weIl as Si on Ge(lOO) by molecular beam epitaxy is studied in-situ with helium atom scattering (TEAS), LEED or STM. During growth with constant deposition parameters at temperatures, where the film structure is determined by kinetics and not thermodynamics, in all three cases three-dimensional structures evolve. Due to a hampered interlayer mass transport, nucleation of higher layer islands sets in before the lower layers are completed. Using the purely kinetic concept of two mobilities, layer-by-Iayer growth in aIl three cases is obtained. This concept is based on creating an artificially enhanced density of islands during the early stage of monolayer growth such that nucleation on top of these sm aller islands is prevented up to the stage of coalescence. However, details of the growth recipes have to be adjusted to the specific kinetics of the system under investigation. In case of Ni/Cu(ll1), interdiffusion limits the applicability of temperature variation to enhance the island density. In the case of Si/Ge(lOO), interlayer mass transport is hampered only at double steps. Hence in this system, growth manipulation is adjusted to avoid the formation of such steps. By measuring the island density or other film properties as a function of temperature or by direct observation of diffusion processes with STM, different microscopic diffusion barriers are estimated