Observation of fluorine-vacancy complexes in silicon

We show direct evidence, obtained by positron annihilation spectroscopy, for the complexing of fluorine with vacancies in silicon. Both float zone and Czochralski silicon wafers were implanted with 30 keV fluorine ions to a fluence of 2x10(14) ions/cm(2), and studied in the as-implanted condition, and after annealing to 650 degreesC for 10 and for 30 min. The "2-detector" background reduction technique for positron annihilation was applied. The spectra reveal a significant concentration of fluorine-vacancy complexes after annealing, for both Czochralski and float zone material, supporting the results of computer simulations of the implantation and annealing process. (C) 2004 American Institute of Physics.