Transformation of Cl bonding structures on Si(100)-(2×1)

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×{}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 [011{}] axes (the axes of Si₂ dimer orientations in two domains). Upon annealing (T{≤}673 K), the Cl⁺ ESDIAD pattern is irreversibly transformed into a four-beam pattern with a twofold azi- muthal symmetry in the plane of each dimer axis, indicative of the formation of energetically stable Si-Cl bonds inclined 25^∘{}±{}4^∘{} from the surface normal.