Two-stage diffusion and nanoparticle formation in heavily implanted polycrystalline Al 2O 3

Abstract

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 RBS spectra, shows two different diffusion mechanisms for the implanted Ti ions between RT and 900°C: (i) radiation enhanced diffusion (RED) up to 730°C; (ii) transient thermal-like diffusion between 730°C and 900°C. The extrapolation to zero-value at 710°C agrees well with the temperature, reported in (G.P. Pells, J. Am. Ceram. Soc. 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°C. Combining RBS, 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.