Si(111)-5 × 2 Au reconstruction was studied dynamically at 500°C by high-temperature scanning tunneling microscopy (STM). Transitions of the 5 × 2 domains during growth were observed as invasive erosions of one domain by another. Whenever this occurred, the domain with its 2-fold direction crossing the domain boundary eroded away. This phenomenon suggests that growth in the 2-fold direction has a stronger driving force. Comparison with STM images taken at room temperature shows that the gold atoms seem to diffuse in the 2-fold direction at higher temperatures. The driving force is believed to derive from repulsion between the gold atoms.
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