X-RAY TRUNCATION ROD STUDY OF GE(001) SURFACE ROUGHENING BY MOLECULAR-BEAM HOMOEPITAXIAL GROWTH

Surface roughness was determined by x-ray diffraction for Ge films on Ge(001) grown by molecular beam epitaxy at room temperature. The trunc ation rod intensities and transverse-scan line profiles were measured as a function of perpendicular momentum transfer. Depending on the ini tial morphology of the surface, the same growth condition resulted in very different. surface morphologies. Two types of initial surfaces we re used. One was an atomically flat surface with very large terraces. The other, characterized by a roughness-exponent alpha=1, had a high d ensity of steps. Deposition on the flat surfaces resulted in a fairly smooth surface, but with a graded crystalline density below the surfac e. Deposition on the alpha=1 surfaces resulted in a more jagged surfac e characterized by an increase in the average height-height correlatio n function and a final roughness exponent of alpha=1/2. Additional and complementary information about the surface structure was obtained by scanning tunneling microscopy observations. (C) 1996 American Institu te of Physics.