Two-stage diffusion and nanoparticle formation in heavily implanted polycrystalline Al2O3

Two-stage diffusion was experimentally observed for the first time in polyc rystalline alumina. Samples were heavily implanted by Ti ions and the conce ntration depth profiles were determined by Rutherford backscattering spectr ometry (RBS) with 2 MeV He+ ions. The Arrhenius-plot, derived from the RES spectra, shows two different diffusion mechanisms for the implanted Ti ions between RT and 900 degreesC: (i) radiation enhanced diffusion (RED) up to 730 degreesC; (ii) transient thermal-like diffusion between 730 degreesC an d 900 degreesC. The extrapolation to zero-value at 710 degreesC agrees well with the temperature, reported in (G.P. Pells, J. Am. Ceram. Sec. 77 (2) ( 1994) 368). At this temperature the annealing of F-centres is already compl eted. High resolution scanning electron microscopy (HSEM) with energy dispe rsive X-ray analysis (EDX) showed Ti-enriched nanoparticles with a typical diameter of about 10-15 nm on samples, implanted at RT. The nanoparticles a gglomerate into larger particles at an implantation temperature of about 83 0 degreesC. Combining RES, HSEM, X-ray photoelectron spectroscopy (XPS) mea surements with TRIM simulations (J.F. Ziegler, J.P. Biersack, U. Littmark, The Stopping and Range of Ions in Solids, Pergamon, New York, 1985), more d etailed information on depth and lateral distribution of Ti atoms was obtai ned. (C) 2000 Elsevier Science B.V. All rights reserved.