Chemical bonding features of fluorine and boron in BF₂⁺ ion implanted Si

The chemical bonding configuraions of fluorine and boron atoms in BF₂⁺ ion implanted Si network have been studied by using x-ray photoelectron spectroscopy, infrared absorption and Raman scattering measurements. It is found that fluorine atoms in as implanted Si are mainly bonded to boron. By annealing at 900°C, BF bonds are thermally decomposed in the matrix and boron atoms are incorporated as four-fold coordinated acceptors, while fluorine atoms form thermodynamically stable SiF_x bonds (x=2,3) which appear to be located in the remaining defects. It is also shown that in the Raman spectra of recrystallized Si the full width at half maximum of the TO mode peak at 520 cm^-1 and the intensity of the Si-B local mode at 620 cm^-1 are well correlated with the BF₂⁺ ion dose and can be used for determining the hole concentration.