Adsorption and structural energetics of chemisorbed F atom Si(100) - a density functional theory (DFT) study

We report density functional electronic structure calculations related to the initial fluorination of the Si(100)-2 x 1 surface. Embedded finite silicon clusters are used to model an extended Si(100)-2 x 1 surface. Two high symmetry pathways and subsequent adsorption sites were examined: (i) adsorption of an fluorine atom directing onto a silicon dangling bond to form a monocoordinated fluorine atom (ii) adsorption of a fluorine atom directing on top of silicon dimer to form a bridging dicoordinated fluorine atom. However, in the later case we find that no barrier exists for the bridging fluorine atom to slide towards silicon dimer dangling bond to form more stable mono coordinated Si-F bond. We calculated activation barriers and equilibrium surface configuration as a function of fluorine coverage upto 2.0 ML. We report the harmonic vibrational frequency for surface fluorosilyl species. We compared the stability of the fluorinated surface. We finally propose a plausible mechanism of the initial stage of fluorine etching.