Dose Rate and Temperature Dependence of Ion-Beam-Induced Defect Evolution in Si and SiC
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Dose Rate and Temperature Dependence of Ion-Beam-Induced Defect Evolution in Si and SiC M. Posselt, L. Bischoff and J. Teichert Institute of Ion Beam Physics and Materials Research, Forschungszentrum Rossendorf, D-01314 Dresden, Germany A. Ster, Research Institute for Technical Physics and Materials Science, H-1525 Budapest, Hungary ABSTRACT A focused ion beam system is applied to investigate the dose dependence of the shape of Ge channeling implantation profiles in Si and SiC at two very different dose rates (1011 and 1018 cm-2 s-1), and for implantation temperatures between room temperature and 580 0C. The competing influence of dose rate and temperature observed is explained in terms of intracascade defect relaxation. For the different implantation temperatures, the time scale for defect reduction is estimated. The results obtained for Si are compared with those for SiC.
INTRODUCTION Ion-beam-induced defect accumulation leads to a dose dependence of the shape of ion range profiles in single-crystalline targets. This effect is caused by the enhanced dechanneling of the implanted particles when radiation damage builds up. It is particularly pronounced for channeling implantation, i.e. if the direction of ion incidence is parallel to low-index axial or planar channels of the crystal. The dose dependence of the profile shape was extensively studied for room temperature (RT) implants into Si using conventional implanters with typical dose rates of 1012 1014 cm-2s-1 (cf. [1,2] and references therein). It was shown that this behavior occurs mainly at doses below and near the amorphization threshold. Atomistic computer simulations demonstrated [1-3] that the relevant defects causing the dechanneling of the incident ions are extended defects like amorphous pockets or clusters of displaced atoms. In this work, the effect of dose rate and implantation temperature on ion-beam-induced buildup of damage in Si and SiC is investigated considering channeling implantation of 70 keV Ge. The use of a focused ion beam (FIB) equipment enables the application of dose rates which differ by seven orders of magnitude. The experimental results are interpreted considering lifetime, relaxation and accumulation of the defects responsible for the dechanneling.
EXPERIMENTS The implantations were performed using the FIB system IMSA-100 [4] with a Au77Ge14Si9 liquid metal ion source [5]. Ge2+ ions were implanted at 70 keV into n-type (001) Si and into ntype (0001) 6H-SiC Lely-platelets. In contrast to common SiC substrates the Lely-platelets do not contain any micropipe defects. Such platelets were used since in present investigations samples with a high crystalline quality are required. The direction of the ion beam was nearly equal to the [001] and [0001] axial channel directions of the Si and SiC samples, respectively. The maximum error of the beam orientation with respect to the crystal axes was about 1.50. This value results F11.2.1 Downloaded from https://www.cambridge.org/core. The Librarian-Seeley Historical Library, on 01 Jan 2020 at 0
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