ADSORPTION OF ELEMENTAL S ON SI(100)-2X1 SURFACES

We have studied the adsorption of elemental S on Si(100)-2 X 1 surface s by LEED, AES, TDS, and WF measurements in UHV. The adsorption of S a t room temperature causes the surface restoration of the reconstructed Si(100)-2 X 1 substrate to its original bulk-terminated surface, Si(1 00)-1 X 1. The S adsorbate follows the substrate structures, i.e. it f orms initially a (2 X 1) up to 0.5 ML and subsequently a (1 X 1). Abov e 1 ML, sulfur is imbedded into the Si bulk near the surface. The stic king coefficient of S on Si(100) surface is constant, S = 1, up to 2 M L. 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 a s SiS molecule with a single TD peak near 585 degrees C. This may indi cate that the Si-S bond energy is greater than that of Si-Si which may be the dominant cause of the substrate restoration.