STM Movie of Adsorbate Induced Step Faceting

This movie was recorded during Br₂ exposure to a Cu surface vicinal to (100).  At the start of the movie, the Cu surface is clean and the Br₂ source is turned on.  The step positions fluctuate until the coverage of adsorbed Br saturates which causes the steps to align parallel to the close-packed directions of the adlayer.  This step faceting occurs quickly over a very narrow coverage range.  Each frame was recorded in 2.5 sec.