Isothermal desorption process of Cl-covered Si(1 1 1) studied by surface differential reflectivity spectroscopy

The isothermal desorption of silicon chlorides from a chlorine-saturated Si(1 1 1) rest atom surface at about 900 K has been investigated by means of in situ real-time surface differential reflectivity spectroscopy. The spectral features at 1.8 eV (A) and 2.5 eV (B) arise mainly from missing adatom dangling bonds and missing adatom back bonds of the dimer–adatom–stacking-fault (DAS) structure, respectively. The feature A decays twice as fast as B does, which indicates that A also originates from the dangling bonds on the rest atom surface. The decay of A, which is considered to represent the desorption of silicon dichlorides, follows first-order kinetics, and the activation energy for this process is 2.3 eV. The decay of B, which is considered to represent the formation of the DAS structure, also follows first-order kinetics and the activation energy is 2.8 eV. The mechanisms of the desorption of silicon dichlorides and the formation of the DAS structure are discussed on the basis of the experimental results.