Structure determination of the Si(111)-(2×1) surface with channeling and blocking

The structure of the cleaved Si(111)-(2×1) has been determined with medium-energy ion scattering using the effects of channeling and blocking. The basic structure arrived at is the -bonded chain model, modified by a tilt in the first- and second-layer chains, of 0.3 (+0.35, -0.45) and -0.15 (+0.25, -0.15), respectively. The first-layer chain is not relaxed significantly. We find that strong enhancement of surface thermal vibrations is needed to obtain good agreement with experimental results. The structural parameters determined do not depend on the detailed choice of vibration amplitudes. © 1984 The American Physical Society.