Surface Science

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

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One monolayer (ML) of Sb, which is the saturation coverage at the substrate temperature Ts = 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 JAr = 1.7 ×1014 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 × 1016 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 T1 = 890°C. In agreement with previous results, the peak was fit with a binding energy E1 = 2.33 eV. Ion irradiation resulted in the formation of an additional, higher temperature, TSD peak at T2 = 1005°C which was fit with E2 = 2.6 eV. The Sb coverage θ2 at the T2 site increased with increasing ion dose, reached a maximum of θ = 0.08 ML at D {all equal to} 8.5 ×1015 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 T1 and T2 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 α2 of Sb adatoms from the T1 into the T2 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 JSb4 = 1.5 ×1013 cm-2 s-1 and the same value of JAr resulted in an increase in the saturation coverage from 1 to 1.6 ML. TSD peaks were observed at both the T1 and T2 positions and an additional broad low-energy TSD peak was obtained at T3 {all equal to} 710 °C. The coverage of Sb bound at the T3 site was ~ 0.25 ML. © 1987.


02 Mar 1987


Surface Science