TRANSFORMATION OF CL BONDING STRUCTURES ON SI(100)-(2X1)

The digital electron-stimulated-desorption ion angular distribution (ESDIAD) method has been used to observe the existence and the irreversible thermal transformation between different bonding structures for Cl on the Si(100)-(2 X 1) surface. The ESDIAD pattern produced from dissociative chemisorption of Cl2 at 120 K shows intense normal emission of Cl+, plus lower intensity of Cl+ emission focused along the [011] and [011BAR] axes (the axes Of Si2 dimer orientations in two domains). Upon annealing (T less-than-or-equal-to 673 K), the Cl+ ESDIAD pattern is irreversibly transformed into a four-beam pattern with a twofold azimuthal symmetry in the plane of each dimer axis, indicative of the formation of energetically stable Si-Cl bonds inclined 25-degrees +/- 4-degrees from the surface normal.