Reactivity of halogens on a Si(111) surface studied by surface differential reflectivity

Abstract

The adsorption of Br on a $\mathrm{Si}(111)7\ifmmode\times\else\texttimes\fi{}7$ surface at room temperature and the isothermal desorption of silicon bromides from a Br-terminated Si(111) rest atom surface at about 900 K have been investigated by means of in situ real-time surface differential reflectivity (SDR) spectroscopy in order to elucidate the fundamental processes of Br-etching. The present results are compared with those of previous SDR studies on chlorine adsorption and chloride desorption. In the adsorption process, both the sticking probability on adatom dangling bonds and the breaking probability of adatom back bonds are larger than those for Cl adsorption. In the desorption process, the activation energy for bromide desorption (1.8 eV) is smaller than that for chloride desorption. The experimental results can be well interpreted in terms of larger repulsive interaction between Br adsorbates. The activation energy for the formation of the dimer-adatom-stacking fault structure (3.5 eV) is larger than that for the surface after chloride desorption.