The  Si(100)-(2x1)  Reconstruction

The pictures below show the ideal, unreconstructed Si(100) surface and the more thermodynamically stable (2x1) reconstructed surface.

A. Unreconstructed Si(100)-(1x1) surface.

The Si atoms of the topmost layer are highlighted in orange; these atoms are bonded to only two other Si atoms, both of which are in the second layer (shaded grey).

B. Reconstructed Si(100)-(2x1) surface.

The Si atoms of the topmost layer form a covalent bond with an adjacent surface atom are thus drawn together as pairs; they are said to form "dimers".

Pictures courtesy of the "WWW Picture Gallery based on the Surface Structure Database (SSD, NIST Standard Reference Database 42) by P. R. Watson, M. A. Van Hove, K. Hermann. The pictures have been prepared from SSD output and postprocessed with BALSAC by K. Hermann"

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