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 t he initial fluorination of the Si(100)-2 x 1 surface. Embedded finite silic on clusters are used to model an extended Si(100)-2 x 1 surface. Two high s ymmetry pathways and subsequent adsorption sites were examined: (i) adsorpt ion of an fluorine atom directing onto a silicon dangling bond to form a mo nocoordinated fluorine atom (ii) adsorption of a fluorine atom directing on top of silicon dimer to form a bridging dicoordinated fluorine atom. Howev er, in the later case we find that no barrier exists for the bridging fluor ine atom to slide towards silicon dimer dangling bond to form more stable m ono coordinated Si-F bond. We calculated activation barriers and equilibriu m 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.