Ion implantation induced formation of aluminum nanoparticles in alumina via reduction

Ion implantation of calcium and yttrium into high-purity, single crystalline a-alumina has resulted in the formation of metallic aluminum nanoparticles in the implanted regions. The calcium implantations were carried out at accelerating energies of 50 and 70 keV and resulted in particles with average diameters of approximately 8.2 +/- 1.4 nm. The yttrium was implanted at an accelerating energy of 150 keV and resulted in particles of approximately 10 +/- 1.8 nm in diameter. The ion fluence for all implantations was 5 x 10(16) ions cm(-2). Differential optical absorption measurements support the presence of nanoparticles in these samples. The spectra from the Ca implanted samples show absorption features at similar to 245 nm. The spectrum from the Y implanted sample shows a similar, but more intense, absorption feature at 239 nm. The particles are face-centered cubic with a calculated lattice parameter of a(o) = 0.41 nm and are randomly oriented and aluminum-rich with respect to the surrounding amorphous alumina matrix. Energy filtering transmission electron microscopy (EFTEM) results confirm that the particles contain metallic aluminum, which is formed as a result of the reduction of the alumina matrix. (C) 1998 Elsevier Science S.A.