This is an SEI image of a Si(111) surface that was heated in a UHV surface science system. The Si(111)7x7 reconstruction is key to the calibration of our UHV AFM-STM. It is formed by taking Si(111), heating to very high temperatures and then quickly cooling.
Low energy electron diffraction-- LEED--was used to study the symmetry of the surface net to determine if the sample had reconstructed before attempting AFM or STM. The LEED never quite looked right. The sample was removed and imaged in SEI mode in the SEM. The surface was covered with triangular defects that are all oriented in the same direction suggesting their edges follow high symmetry directions in the Si(111). A little cluster of material was in the center of each.