For a characterization of interface and “bulk” properties of Ge films grown on Si(111) by Sb surfactant-mediated epitaxy, grazing incidence x-ray diffraction and transmission electron microscopy have been used. The interface roughness, defect structure, and strain state have been investigated in dependence of film thickness and growth temperature. For all growth parameters, atomically smooth interfaces are observed. For thin Ge layers, about 75% of the strain induced by the lattice mismatch is relaxed by misfit dislocations at the Ge∕Si interface. Only a slight increase of the degree of relaxation is found for thicker films. At growth temperatures below about 600°C, the formation of twins is observed, which can be avoided at higher temperatures.
A very compact molecular beam epitaxy (MBE) source is presented. It contains three Knudsen-type crucibles, two resistively and one electron bombardment heated. An efficient water cooling is implemented to allow MBE deposition under ultrahigh-vacuum conditions. Due to its small size, the evaporator fits inside a DN 36 CF T-piece which makes a separate bakeout possible. Refills of the crucibles as well as changes of the source materials and even repairs of the source can be carried out within a few hours without breaking the vacuum of the main chamber. The design and the usage of the MBE source are described in detail and its functionality is demonstrated exemplarily with data of silver deposition on the silicon (111) surface.
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