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Characterization of carbon implanted fused silica samples using RBS and ERDA

Fused quartz implanted with C ions with different energies and implantation doses were investigated using non-Rutherford Backscattering Spectroscopy and Elastic Recoil Detection Analysis. Samples were analized under same conditions before and after annealing in forming gas to study mobility of carbon and hydrogen atoms in the substrate. For the analysis of samples implanted with 64 and 320 keV ions, we have used 4He beam and applied the fact that the cross sections for 12C(α , α )12C between 3.5 and 4 MeV are almost constant and 7 times Rutherford at 165°. This enhancement was sufficient to determine concentration and depth profile of carbon in SiO2 matrix in only one measurement. For samples implanted by more energetic (1 and 1.5 MeV) ions, carbon concentration and depth distribution were studied using proton beam and strong resonance in 12C(p, p)12C elastic scattering at 1726 keV. Proton beam measurements were applied to monitor amount of carbon diffused from the implanted region due to annealing. Multiple measurements are required for the study of carbon depth profile. By comparing the shape of the backscattering spectra at the same proton energy before and after heating, structural changes due to annealing process were observed. Hydrogen was studied by ERDA using 6.5 MeV oxygen ions. Forward scattered O ions as well as H recoils were detected using the IEE ERDA system that provides good separation between the two ion types and results in a background free H depth spectrum. Detector was placed at 45° scattering angle, with 22, 5° angle between the ion beam and the sample surface. With this experimental setup we could analyze hydrogen in SiO2 matrix up to 700 nm depth. Diffusion of hydrogen atoms from the environment into the substrate during the annealing was observed. Hydrogen atoms were accumulating at the as-implanted carbon positions.

RBS; ERDA; silica samples

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