Influence of ion bombardment on the interaction of Sb with the Si(100) surface

Abstract

One monolayer (ML) of Sb, which is the saturation coverage at the substrate temperature T s = 425 °C used in these experiments, was adsorbed on clean Si(100) surfaces and subsequently bombarded with 2 keV Ar + ions incident at an angle of 21° and a flux J Ar = 1.7 ×10 14 cm −2 s −2. Thermally-stimulated desorption (TSD) was then used to measure the remaining Sb coverage θ as a function of ion dose D (0 to 2.3 × 10 16 cm −2) and to determine the effect of ion irradiation on the Sb surface binding energy. In the absence of ion bombardment, only one TSD peak was observed which, at a heating rate of 10 °C s −1, occurred at T 1 = 890°C. In agreement with previous results, the peak was fit with a binding energy E 1 = 2.33 eV. Ion irradiation resulted in the formation of an additional, higher temperature, TSD peak at T 2 = 1005°C which was fit with E 2 = 2.6 eV. The Sb coverage θ 2 at the T 2 site increased with increasing ion dose, reached a maximum of θ = 0.08 ML at D ≌ 8.5 ×10 15 cm −2 , and then gradually decreased. A simple model, which includes terms for ion-bombardment-induced sputtering and trapping processes, was used to calculate Sb coverages on both the T 1 and T 2 sites as a function of D and shown to be in good agreement with experimental results. The sputtering yield S from the two sites was found to be ~ 0.08 atoms/ion and the trapping yield α 2 of Sb adatoms from the T 1 into the T 2 site was 0.015 atoms/ion. The low value of S was due primarily to the poor mass matches between Ar/Sb and Si/Sb. Ion bombardment carried out during Sb deposition on Si(100) with J Sb 4 = 1.5 ×10 13 cm −2 s −1 and the same value of J Ar resulted in an increase in the saturation coverage from 1 to 1.6 ML. TSD peaks were observed at both the T 1 and T 2 positions and an additional broad low-energy TSD peak was obtained at T 3 ≌ 710 ° C . The coverage of Sb bound at the T 3 site was ~ 0.25 ML.