IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Semiconductors Friday Sessions
       Session SC+SS-FrM

Paper SC+SS-FrM2
STM Observations of the Initial Growth Process of Ge on Si(105) Surfaces: the Stability of Ge/Si(105) Surfaces

Friday, November 2, 2001, 8:40 am, Room 111

Session: Growth and Epitaxy of Semiconductors
Presenter: Y. Fujikawa, University of Wisconsin-Madison
Authors: Y. Fujikawa, University of Wisconsin-Madison
T. Sakurai, Tohoku University, Japan
M.G. Lagally, University of Wisconsin-Madison
Correspondent: Click to Email
The mechanism of the formation of self-organized SiGe quantum dots on the Si(100) surface has been intensively investigated because of the technological importance of achieving uniform size and high order in the dots. Although it has been demonstrated that the strain created by the lattice mismatch between Ge and Si plays an important role in the transition to 3D island growth and in 3D island ordering, there still is no satisfactory explanation of SiGe(105) facet formation, which creates the regular shape of the SiGe islands. We have used STM to observe the surface structures formed when Ge is deposited on Si(105) surfaces, in order to clarify the coverage dependence of the stability of the (105) surface. When the Ge coverage is greater than 0.5 ML, a p(2x1) reconstructed stable surface is observed, as previously reported.@footnote 1@ At a coverage of ~ 0.5 ML or less, we observe formation of a p(4x1) structure over parts of the surface. The transformation to a p(4x1) structure is complete at 0.04 ML coverage. Decreasing the Ge coverage to 0.02 ML results in roughening of the Si(105) surface. During the transition from the p(2x1) to the p(4x1) structure, a significant change in surface morphology is observed. At coverages of 0.2 ML or less, the formation of the topmost layer tends to start from upper-step edges, while it starts from lower-step edges for coverages above 0.2 ML. As a result, defect arrays are frequently observed at the lower-step edges when the coverage is 0.2 ML or less, due to the incomplete formation of the topmost layer at the lower-step edges. This result clearly indicates the presence of increased strain on the Ge/Si(105) surface as the coverage of Ge is reduced. Ge thus stabilizes the surface. This work is partially supported by NSF and by the Ministry of Education, Culture, Sports, Science and Technology, Japan. @FootnoteText@ @footnote 1@ Tomitori et al., Surf. Sci. 301 (1994) 214.