The effect of incident energy upon adsorbate structure for Cl2 chemisorption onto Si(111)-7×7 surfaces

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Abstract
Scanning tunneling microscopy (STM) and molecular beam techniques are used to investigate the effect of adsorption mechanism upon adsorbate structures for Cl2 chemisorption onto Si(111)-7×7 surfaces. At incident energies less than 0.11 eV, the SiCl island formation as well as isolated-site reaction are observed. STM images of the internal structure of the islands show that the SiCl islands nucleate at sublimation defects and not at step edges. Conversely, for 0.44 eV dosing, only the isolated-site reaction occurs. It is proposed that the island formation results from precursor mediated chemisorption and that the isolated-site reaction results from direct activated chemisorption. For direct activated chemisorption, the competition between Cl-atom abstraction and dissociative chemisorption was also observed. The abstraction probability decreases with increasing Cl2 incident translational energy.