Okayama University of Science, Okayama
Si(100) surface is reconstructed in 2×1 structure, where two adjacent surface Si atoms form dimers. Hydrogen molecules can adsorb on the top Si atoms; one H on each Si atom up to coverage 1 ML. Above this coverage, The dimer structure is rearranged to form local 3×1 structures.
| $\theta<1{\rm ML}$ 2×1 structure with mono-hydrides | $\theta<4/3{\rm ML}$ 3×1 structure di- and mono-hydrides* |
*Y. J. Chabal, et al., Phys. Rev. Lett. 54 (1985) 1055.
Experimental TPD Spectra, K. Sinniah et al., J. Chem. Phys. 92 (1990) 5700.
The TPD spectra feature two majour peaks. The alpha-peak appears for initial coverage over 1 ML. This peak is considered to correspond to the desorption from di-hydride states. Only the beta-peak is observed for initial coverage below 1 ML. This peak is considered to correspond to the desorption from mono-hydride states.
The peak position shifts little with coverage change. The peaks are almost symmetric in shape, which are typical characteristics of a first order non-interacting desorption. However, this desorption is known to be an associative desorption, which involves interactions between adsorbates. The interactions are expected to cause large peak shift and asymmetric peak shapes. The purpose of this study is to clarify the cause of this unusual behaviour.
Conclusion (important effects for TPD)
Summary