It was noted that reconstruction of the (001)-2x1 surface involved asymmetrical and buckled Si dimers. The vertical separation between the up and down atoms within the dimer was about 0.072nm, and the dimer bond length was 0.224nm. The latter was slightly smaller than the Si-Si distance in the bulk. The tilt of the dimer was 19. The formation of Si dimers produced marked distortions, in the substrate, which were detectable down to the fifth Si layer.

H.Over, J.Wasserfall, W.Ranke, C.Ambiatello, R.Sawitzki, D.Wolf, W.Moritz: Physical Review B, 1997, 55[7], 4731-6