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

Two-stage diffusion was experimentally observed for the first time in polycrystalline alumina. Samples were heavily implanted by Ti ions and the concentration depth profiles were determined by Rutherford backscattering spectrometry (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 and 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 completed. High resolution scanning electron microscopy (HSEM) with energy dispersive X-ray analysis (EDX) showed Ti-enriched nanoparticles with a typical diameter of about 10-15 nm on samples, implanted at RT. The nanoparticles agglomerate into larger particles at an implantation temperature of about 830 degreesC. Combining RES, HSEM, X-ray photoelectron spectroscopy (XPS) measurements with TRIM simulations (J.F. Ziegler, J.P. Biersack, U. Littmark, The Stopping and Range of Ions in Solids, Pergamon, New York, 1985), more detailed information on depth and lateral distribution of Ti atoms was obtained. (C) 2000 Elsevier Science B.V. All rights reserved.