Implantation parameters affecting aluminum nano-particle formation in alumina

The formation of nano-dimensional metallic Al precipitates in alumina due t o the reduction of the host matrix as a result of ambient temperature ion i mplantation of Y ions is examined. The formation and growth of Al precipita tes are dependent on both the Y ion dose and the energy available to the ma trix, as reported here. Reducing the ion dose from 5 x 10(16) to 2.5 x 10(1 6) ions/cm(2) results in smaller precipitates; 10.7 +/- 1.8 nm to 9.0 nm +/ - 1.2 nm, respectively, for incident ion energies of 150 keV, based upon pa rticle size measurements obtained using energy filtered transmission electr on microscopy. Below a fluence of 2.5 x 10(16), particle formation is not d etected. The energy available to the matrix was varied; first, by controlli ng the incident ion energy (varied between 60 and 150 keV) while holding th e substrate at ambient temperature, and second, by controlling the substrat e temperature (varied between 44 and 873 K) while holding the incident ion energy constant at 150 keV. Experiments conducted with incident ion energie s of 110 keV or higher produce crystalline Al precipitates; whereas implant ations at 100 keV produce amorphous Al particles and implantations at 60 ke V produce no detectable precipitates. The implantations carried out as a fu nction of temperature produce successively smaller precipitates with decrea sing temperature to 77 K (6.7 +/- 1.0 nm), below which no precipitates are detected. An Arrhenius activation energy for the formation of the aluminum precipitates of 1.7 kJ/mole has been calculated using the volume of precipi tates formed as a function of inverse temperature. This low activation ener gy suggests that radiation enhanced diffusion (RED) is responsible for part icle growth during these implantations. (C) 2001 Kluwer Academic Publishers .