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

Invited Paper SC+SS-FrM5
Formation and Decay Processes of Silicon Mounds on Si(111) Surfaces

Friday, November 2, 2001, 9:40 am, Room 111

Session: Growth and Epitaxy of Semiconductors
Presenter: A. Ichimiya, Nagoya University, Japan
Authors: A. Ichimiya, Nagoya University, Japan
K. Hayashi, Nagoya University, Japan
E.D. Williams, University of Maryland
T.L. Einstein, University of Maryland
M. Uwaha, Nagoya University, Japan
Correspondent: Click to Email
Two types of isolated single silicon pyramids on the Si(111) surfaces between 700K and 800K have been produced using an STM tip. Pyramids of 75% are normal stacking at the interface between the pyramid and the substrate (called type U). For pyramids of 25% which are in the twin relation of the type U pyramids, there is a stacking fault at the interface (called type F). The pyramids have certain facets just after the creation. Indices of main facets of the mounds on the Si(111) surface are {311}, and small facets are {221} for the type U and {331} for the type F. Just after the production, the pyramid begins to decompose. During the decay of the type U pyramid, the facets of the pyramid transform into multi-bilayer steps. Finally the mound becomes a bilayer mound (2D) with a truncated triangle shape. The longer edges of the 2D mounds are along the unfaulted halves of the DAS structure of the substrate, while these edges are the shorter one of the pyramid. The decay process of the type F pyramid is layer-by-layer without step bunching. Decay rates of the type F pyramids are about 3 times larger than those of the type U due to the stacking. The energy state of the type F pyramids is about 0.06eV higher than that of the type U. We have measured height evolution of the pyramids during decay, and found that the height decay is due to the power law , t@super 1/4@, where t is the decay time. Such the simple law is predicted by Israeli and Kandel@footnote 1@ for infinite cone decay. It should be noted that such the simple law is in very good agreement with the experimental results of silicon pyramid decay. The results are explained by attachment-detachment limited processes at step edges. The measured decay rates are in very good agreement with decay rates which are evaluated from those of 2D mounds.@footnote 2@ @FootnoteText@ @footnote 1@ N. Israeli and D. Kandel, Phys. Rev. Lett. 80, 556 (1998. @footnote 2@ A. Ichimiya, Y. Tanaka and K. Ishiyama, Phys. Rev. Lett. 76, 4721 (1996).