Electron paramagnetic resonance of silica glasses implanted with nickel

Abstract Silica substrates were implanted with Ni + ions to nominal fluences ( F ) ranging from 10 15 to 6×10 16 cm −2 at energy E =160 keV. The anisotropic spectrum of electron paramagnetic resonance with g || =2.49±0.03 and g ⊥ =2.17±0.03 was observed at 77 and 295 K for the samples implanted to F =(1–3)×10 15 cm −2 and was attributed to Ni + ions with ground state | xy 〉 or | x 2 − y 2 〉. The single line with g =2.29 and Δ H pp ∼14 mT was found at 77 and 295 K for the samples implanted to F =(4–8)×10 15 cm −2 and was assigned to clusters of Ni + ions coupled by exchange interactions. Starting from F =8×10 15 cm −2 and at higher fluences the single line with g ∼2.2 and Δ H pp ∼30–40 mT was observed at room temperature. The behavior of this line as function of measurement temperature indicates its superparamagnetic origin earlier studied by Isobe et al. Optical absorption spectra and transmission electron microscopy confirm the results obtained by other authors concerning the formation of particles of metallic nickel of nanometer size in silica glass implanted with Ni + to F >10 16 cm −2 .