Structure and optical properties of sapphire implanted with boron at room temperature and 1000 °C Carl J. McHargue a, * , E. Alves b,c , L.C. Ononye a , C. Marques b,c a Center for Materials Processsing, University of Tennessee, 100 Eastbrook Hall, Knoxville, TN 37996-0750, United States b Dep. Fisica, Instituto Tecnologico e Nuclear, Sacave´m 2686-953, Portugal c Centro de Fisica Nuclear da Universidade de Lisboa, Lisbon, Portugal Available online 12 June 2006 Abstract Many previous studies of ion-implanted sapphire have used gas-forming light ions or heavier metallic cations. In this study, boron (10 17 cm 2 , 150 keV) was implanted in c-axis crystals at room temperature, 500 and 1000 °C as part of a continuing study of cascade density and ‘‘chemical’’ effects on the structure of sapphire. Rutherford backscattering-ion channeling (RBS-C) of the RT samples indi- cated little residual disorder in the Al-sublattice to a depth of 50–75 nm but almost random scattering at the depth of peak damage energy deposition. The transmission electron micrographs contain ‘‘black-spot’’ damage features. The residual disorder is much less at all depths for samples implanted at 1000 °C. The TEM photographs show a coarse ‘‘black-spot damage’’ microstructure. The optical absorption at 205 nm is much greater than for samples implanted with C, N, or Fe under similar conditions. Ó 2006 Elsevier B.V. All rights reserved. PACS: 61.72.Yx; 61.82.Ms Keywords: Ion implantation; Sapphire, Defect structure 1. Introduction Many details of the defect structure produced by ion implantation of sapphire (single crystal a-Al 2 O 3 ) have been studied and a general understanding has been achieved. Sapphire exhibits essentially no deviation from stoichiome- try and limited solubility of impurities. The nonequilibrium introduction of implanted species requires the formation of second phases and/or defect-impurity complexes that com- pensate for unbalanced charges. Implantation of inert gases at fluences P10 17 ions cm 2 causes blisters and exfoliation of the surface [1]. Transmis- sion electron microscopy has detected bubbles in RT nitro- gen-implanted sapphire at fluences as low as 3 · 10 16 N cm 2 [2]. This band of bubbles causes de-channeling in the RBS-C spectra. Blistering and exfoliation of the surface have been reported for RT implantation of 2 · 10 17 N cm 2 [3]. Alves et al. detected a second source of de-channeling in the Al-sublattice at the depth of the Al recoils and suggested that it might be due to Al-interstitials [4]. Many implanted cations form nanometer-sized metallic particles at fluences greater than about 3 · 10 16 ions cm 2 . As an example, as much as 50% of iron is in this form for implantations fluences of 10 17 Fe cm 2 [5]. The remaining Fe resides in the valence states of Fe 2+ and Fe 4+ that are associated with oxygen vacancies that contain trapped elec- trons (i.e. F- and F + -centers). A study of boron implantation is of interest for several reasons. The usual valence is 3+, the same as Al, thus it might replace Al on the Al-sublattice. The damage cas- cades for light ions differ significantly from those of heavier ions. Simulations using SRIM 2004 show that the displaced Al and O and the implanted B exhibit negative skewness of the range distributions, whereas, implantation of heavier 0168-583X/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2006.04.086 * Corresponding author. Tel.: +1 865 974 7680; fax: +1 865 974 4995. E-mail address: crl@utk.ed (C.J. McHargue). www.elsevier.com/locate/nimb Nuclear Instruments and Methods in Physics Research B 250 (2006) 81–84 NIM B Beam Interactions with Materials & Atoms