Precipitation, ripening and chemical eects during annealing of Ge  implanted SiO 2 layers K.H. Heinig a , B. Schmidt a, * , A. Markwitz a , R. Gr otzschel a , M. Strobel a , S. Oswald b a Forschungszentrum Rossendorf, Institut f  ur Ionenstrahlphysik und Materialforschung, PO Box 510119, D-01314 Dresden, Germany b IFW Dresden, Institut f  ur Festk orperanalytik und Strukturforschung, PO Box 270016, D-01171 Dresden, Germany Abstract The Ge redistribution and nanocrystal formation in Ge  implanted SiO 2 layers have been systematically studied by RBS, TEM and XPS. Annealing in N 2 or Ar leads to a dramatic change of the as-implanted Gaussian-like Ge depth distribution to a bimodal pro®le and, additionally, an accumulation of Ge at the Si/SiO 2 interface. XTEM images show no Ge nanocrystals in the region of the sub-surface peak, whereas the deeper peak can be clearly related to Ge nanocrystals. A similar Ge redistribution occurs after annealing in pure O 2 , but in this case amorphous GeO x clusters have been found too. The annealing behaviour is explained by the in-diusion of an oxidant (O 2 or a few ppm of moisture) from the annealing ambient and its subsequent reaction with dissolved and/or clustered Ge. Kinetic 3D lattice Monte-Carlo simulations have been performed to prove this model of the Ge redistribution and nanocluster evolu- tion. Ó 1999 Elsevier Science B.V. All rights reserved. PACS: 61.46.+w; 61.16.Bg; 81.20.)n; 82.80.Yc; 07.05.Tp Keywords: Ion-beam synthesis; Germanium; Silicon dioxide; Annealing; Oxidation; Modeling 1. Introduction High-dose ion implantation allows to implant surface layers with impurity atoms up to high concentrations. If the implanted impurity atoms are not miscible with the substrate, nanoclusters can precipitate. If diusion of impurity atoms is small during implantation, a post-implantation annealing step initiates precipitation of nanoclus- ters followed by their growth and coarsening. By this ion beam synthesis (IBS) technique metallic, semiconducting or insulating nanoclusters in var- ious substrates can be obtained. Particularly in- teresting are nanoclusters of elemental semiconductors (Si, Ge) in SiO 2 due to their lu- minesence (see e.g. [1,2]) and their potential use for non-volatile memory devices (see, e.g., [3±5]). The impurity redistribution and nanocrystal evolution can be strongly in¯uenced by the an- nealing ambient as has been reported recently [6] for Ge implanted SiO 2 layers. The origin of this behavior is in-diusion of an oxidant from the annealing atmosphere, which changes substantially the Ge depth pro®le and nanocluster distribution. Nuclear Instruments and Methods in Physics Research B 148 (1999) 969±974 * Corresponding author. Tel.: +49 351 260 2726; fax: +49 351 260 3285; e-mail: bernd.schmidt@fz-rossendorf.de 0168-583X/98/$ ± see front matter Ó 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 9 8 ) 0 0 8 6 2 - 3