Adsorption of chlorine on Si(100)

The adsorption of Cl₂ on Si(100) has been examined by temperature-programmed desorption and low-energy electron diffraction. The results reconcile disagreement in the literature about whether SiCl₂ or SiCl₄ desorbs at 950 K from Si surfaces in response to Cl-containing gases. Either product can be obtained, depending on the history of the ultra-high vacuum chamber. SiCl₄ desorption is a spurious effect that arises from the presence of gaseous FeCl₃, which forms in the chamber after large Cl₂ exposures. SiCl₂ is the true product, desorbing by second-order kinetics with an activation energy of 73 ∓ 4 kcal/mol and a pre-exponential factor n₀v₀ = 4×10^16∓1 s^-1. For large Cl₂ exposures, the surface is etched through SiCl₄ desorption at 500 K, and at 115 and 150 K in the presence of Cl₂ multilayers.