Dynamic computer simulations of Cs incorporation in Si during low‐energy (0.2–3 keV) irradiation

Abstract

AbstractThe incorporation of Cs atoms in silicon was investigated by dynamic computer simulations using the Monte‐Carlo code T‐DYN that takes into account the gradual change of the target composition due to the Cs irradiation. The implantation of Cs atoms at normal incidence was studied for four energies (0.2, 0.5, 1, and 3 keV) and three different Cs surface‐binding energies UCs (0.4, 0.8, and 2.4 eV). The total implantation fluences were 2 × 1017 Cs cm−2 for 0.2 keV, 1.5 × 1017 Cs cm−2 for 0.5 keV, and 1 × 1017 Cs cm−2 for 1 and 3 keV. At these values, a stationary state has been reached. The steady‐state Cs‐surface concentrations exhibit a pronounced dependence both on impact energy and UCs, varying between ∼1 (at 0.2 keV and UCs = 2.4 eV) and ∼0.13 (3 keV and UCs = 0.4 eV). Under equilibrium, the partial sputtering yield of Si, YSi, experiences little influence of UCs, but varies with the Cs energy: at UCs = 0.8 eV from 0.09 to 1.0 Si atoms/Cs projectile. For all irradiation conditions a strongly preferential sputtering of Cs atoms as compared to Si atoms is found, increasing from 1.8 (at 3 keV and UCs = 2.4 eV) to 13.3 (at 0.2 keV and UCs = 0.4 eV). Preferential sputtering of Cs increases with decreasing irradiation energy and decreasing UCs. Copyright © 2008 John Wiley & Sons, Ltd.