Surface Structure of Fluorinated Si（100）

The structure of a fluorinated Si（100） surface is studied by He atom diffraction. He diffraction measurements show that Si dangling bonds are the sites for fluorine adsorption. Molecular fluorine reaction with Si（100） 2×1 does not perturb the Si-Si dimer bond and the reaction virtually ceases at one monolayer of F coverage for F₂ at low incident kinetic energy. Further reaction of F₂ with fluorinated surface can be activated by increasing the F₂ incident energy. No ordered surface structure is observed after exposure to high energy fluorine.