DIFFRACTION FROM SMALL ANTIPHASE DOMAINS - ALPHA-ROOT-3X-ROOT-3, BETA-ROOT-3X-ROOT-3, 6 X 6 PHASES OF AU ADSORBED SI(111)

Correlation between domain-wall configurations and electron diffractio n patterns of the Au-adsorbed Si(111) surface was studied by scanning tunneling microscopy (STM), reflection-high-energy electron diffractio n (RHEED), and low-energy electron diffraction (LEED) as a function of Au coverage, Streaks and rings around superreflections in alpha- root 3 X root 3 (LEED) patterns reflect the zigzagging feature and average size of the small root 3 X root 3 domains. These fine structures beco me diffuser and then convert to the beta- root 3 X root 3 pattern in a continuous way with the increase of Au coverage. This evolution in th e diffraction pattern is explained in terms of domain size contraction to a minimum size equivalent to six times of the substrate unit mesh. These smallest domains with dense antiphase domain walls in the beta- root 3 X root 3 phase transform to the 6 X 6 phase by annealing aroun d 600 K, where the smallest domains arrange in a long-range order. Thi s structure transformation may be expressed as 'recrystallization' in the arrangement of small antiphase root 3 X root 3 domains. (C) 1998 E lsevier Science B.V. All rights reserved.