Atomic structure of the cleavedSi(111)−(2×1)surface refined by dynamical LEED

Abstract

New or modified models have been proposed for the much-studied Si(111)-(2x1) surface structure, including: a reverse-tilted π-bonded chain model (by Zitzlsperger et al); a three-bond scission model (by Haneman et al); and a π-bonded chain model with enhanced vibrations (present work). These models are compared here to the generally accepted modified π-bonded chain model (by Himpsel et al, 1984), by analyzing low-energy electron diffraction (LEED) I-V curves measured earlier. Using the efficient automated tensor LEED technique, the models can be refined to a much greater degree than with earlier methods of LEED analysis. This study distinctly favors the earlier modified π-bonded chain model, but with strongly enhanced vibrations.To compare models that have different numbers of adjustable free parameters a Hamilton ratio test is used: it can distinguish between improvement due to a better model and improvement due only to more parameters.

Systematic investigation of the structure of the Si(553)-Au surface from first principles

“…71,72 Experimentally, the positive-tilt structure has been traditionally favored. [68][69][70] In the case of the Si͑553͒ stepped surface, our calculations predict the negative-tilt structure to be slightly more stable.…”

“…There are two possibilities, which are usually referred to as a negative or a positive tilt. 70 In our notation, these two different tilts of the chain are indicated by the order of the pair of indices, with the second index corresponding to the higher atom. In Fig.…”

“…Our most stable geometry ͑model p0͒ correspond to the so-called negatively tilted -bonded chain. 70 In low energy electron diffraction experiments of the flat Si͑111͒ surface, the positive-tilt -bonded chain is usually favored over the negative tilt. [68][69][70] However, first-principles DFT calculations predict both structure to be very close in energy and there are conflicting claims about which of them is more stable.…”

Enhanced Vibrations at Surfaces with Back-Bonds Nearly Parallel to the Surface

“…Since the earlier determination of the modified Pandey model 14 , a series of new or modified models had been proposed for this much-studied surface structure, including a reverse-tilted π-bonded chain model 15 , a three-bond scission model 16 , and a π-bonded chain model with enhanced vibrations 12 .…”

“…Figure 4 shows the Si(111)-(2x1) surface structure. Using LEED, this structure was recently re-analyzed and refined, showing that the "modified Pandey model" remains valid, but involves strongly enhanced vibration amplitudes of the outermost atoms 12 .…”