Formation and decay processes of three-dimensional silicon islands on the Si(111)7x7 surface

Formation process and thermal relaxation of three-dimensional islands like pyramids have been investigated by a temperature-variable scanning tunnelin g microscopy (STM). Isolated single islands on the Si(lll) (7 x 7) surface between 700 and 750 K have been produced using an STM. It is found that isl and is produced with a small distance between the tip and the sample substr ate, and sample polarity does not affect island formation. Indices of main facets of the pyramid are (311), and small facets are (221). Two types of p yramids are produced. Islands with production probability of 75% are normal stacking at the interface between the island and the substrate, and called type N. For islands with production probability of 25%, which are in the t win relation of the type N islands, there is a stacking fault at the interf ace, and called type F. Decay rate of the type F island is larger than that of type N. During decomposition of type N, the facets of the pyramid are s plit into two parts. For the type F islands, the pyramids decay nearly laye r-by-layer without splitting and step bunching. (C) 2000 Elsevier Science B .V. All rights reserved.