Surface atomic geometry of Si(001)-(2×1): A low-energy electron-diffraction structure analysis

The reconstruction of the Si(001)-2×1 surface consists of asymmetric and buckled Si dimers. The vertical separation between the up and the down atom within the dimer is about 0.72±0.05 A and the dimer bond length of 2.24±0.08 A has been found to be slightly smaller than the Si-Si distance in the bulk. The tilt of the dimer is 19±2°. The formation of Si dimers induces pronounced distortions in the substrate that were detectable down to the fifth Si layer. The structure determination is based on two independent low-energy electron-diffraction data sets taken in two different laboratories. The structural results agree well within the error limits, though noticeable differences occur between the experimental data sets. These differences in the experimental data can possibly be attributed to different preparation procedures.