Ion induced precipitation of metal particles in triethoxysilane for optical and magnetic applications

Ion irradiation of silicon-based gels with the stoichiometry SiO1.5H1, prepared from triethoxysilane, and containing Fe3+, Ni2+ or Cu2+ ions in solid solution permits to obtain the precipitation of metallic nanoparticles. Comparison of the particles volume fractions in films irradiated with 1.5 MeV He or 3 MeV Art ions on basis of their optical absorption or magnetic resonance indicates that electronic excitations are responsible for the reduction and precipitation processes, while atomic displacements induce a partial redissolution by mixing. Moreover, the precipitation yield increases almost in proportion to the ion fluence. Measurements of magnetization as a function of the temperature show that the Fe and Ni particles in irradiated films are superparamagnetic and their range of sizes is narrower than in films heat treated in vacuum at 600-1000 degreesC. (C) 2003 Elsevier B.V. All rights reserved.