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 n0nu0 = 4 X 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.