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Ion implantation and thermal processing were used to create a layer of Co nanoclusters embedded in the near-surface region of single-crystal sapphire. The Co nanoparticles ranged in size from 2-20 nm and were crystallographically aligned with the host sapphire. Specimens were irradiated with Xe and Pt ions, and the microstructural evolution of the nanoclusters was investigated by transmission electron microscopy. With increasing Pt or Xe ion dose, the Co nanoparticles lost their initially excellent faceting, although they remained crystalline. The host Al2O3 became amorphous and the resulting microstructure consisted of a buried amorphous layer containing the still-crystalline Co nanoparticles. EDS mapping and electron diffraction were used to determine the distribution of the implanted species, and the magnetic properties of the composite were measured with a SQUID magnetometer. The results show that ion beams can be applied to modify and control the properties of ferromagnetic nanocomposites, and, combined with lithographic techniques, will find applications in exercising fine-scale spatial control over the properties of magnetic materials.

Nanocrystals of CdS and CdSe have been formed in SiO2, Al2O3, and Si by sequential ion implantation and annealing. In SiO2, the nanocrystals have the hexagonal wurtzite structure and are randomly oriented. In Al2O3 and Si, nanocrystals are three dimensionally oriented. They have the cubic zincblende structure in Si and can be produced with either structure in Al2O3 by controlling the implantation conditions. In SiO2 and Al2O3, nanocrystals exhibit strong optical absorption and photoluminescence (PL). Evidence for quantum confinement is observed, and the PL results for CdSe are strongly temperature dependent.

The surface scattering of MeV He+ ions channeled along Si〈100〉 from clean well‐characterized Si(100) surfaces is measured. The surface peak intensity, along with other values in the literature, is shown to obey simple scaling laws. For the study of very thin films by backscattering the contribution made by this surface scattering can be important.