Adsorption of elemental S on Si(100)-2x1 surfaces

We have studied the adsorption of elemental S on Si(100)-2 X 1 surfaces by LEED, AES, TDS, and WF measurements in UHV. The adsorption of S at room temperature causes the surface restoration of the reconstructed Si(100)-2 X 1 substrate to its original bulk-terminated surface, Si(100)-1 X 1. The S adsorbate follows the substrate structures, i.e. it forms initially a (2 X 1) up to 0.5 ML and subsequently a (1 X 1). Above 1 ML, sulfur is imbedded into the Si bulk near the surface. The sticking coefficient of S on Si(100) surface is constant, S = 1, up to 2 ML. Deposition of S at RT up to 1 ML increases the WF of the surface by about 0.30 +/- 0.05 eV. Above 1 ML, as the S is diffused into the Si bulk, the WF decreases, The TDS measurements show that S is desorbed as SiS molecule with a single TD peak near 585 degrees C. This may indicate that the Si-S bond energy is greater than that of Si-Si which may be the dominant cause of the substrate restoration.