Surface roughening induced by a characteristic surface structure of a Si film grown on Si(111)

The changes in the surface morphology and the surface structure reconstruct ion on a Si film grown on Si(1 1 1) 7 x 7 superlattice held at T-s= 250 deg reesC are observed with scanning tunneling microscopy and reflection high-e nergy electron diffraction. The surface morphology of the Si layer has begu n to roughen immediately when the film thickness (d) is above 10 nm. The su rface structure reconstruction on the growing Si film also changes with inc reased film thickness: at the initial growth stage (d < 10 nm), the island showing the 5 x 5 dimer-adatom-stacking fault layer structure is predominan tly formed, while atomic-row structures (c2 x 4 and 2 x 1) along the (1 (1) over bar 0) directions increase with the reduction of 5 x 5 islands in d > 10 nm. The atomic-row structure will relate to the surface roughening, bec ause the atomic-row structure increases with roughening of the surface. We also found a characteristic structure composed of the atomic-rows and propo se a structure model which includes double twin boundaries underneath. The structure has a higher growth rate compared with that in the growth on the (1 1 1) surface. (C) 2001 Elsevier Science B.V. All rights reserved.