TEM and PL Study of FeSi 2 Precipitates Formed in Si by Iron Implantation Using a Metal Vapor Vacuum Arc Ion Source
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F8.20.1
TEM and PL Study of FeSi2 Precipitates Formed in Si by Iron Implantation Using a Metal Vapor Vacuum Arc Ion Source Y. Gao*, W.Y. Cheung*, S.P. Wong*#, G. Shao**, K.P. Homewood*** *Dept. of Electronic Engineering and Materials Science and Technology Research Centre, The Chinese University of Hong Kong, Hong Kong, China **School of Engineering, University of Surrey, Guilford, Surrey GU2 7XH, UK ***School of Electronics Engineering, Computer and Mathematics, University of Surrey, Guildford, Surrey GU2 7XH, UK
ABSTRACT In this work, FeSi2 precipitates were formed in Si by iron implantation using a metal vapor vacuum arc ion source. Transmission electron microscopy (TEM) was used to determine the crystal and defect structures of the implanted samples. It was found that the implantation temperature played an important role on the shape and phase formation of the FeSi2 precipitates, as well as the formation and distribution of the dislocation loops. When implantation was performed at an elevated temperature of about 380oC, there were a lot of dislocation loops formed and only β-FeSi2 precipitates were observed. When implanted at a low temperature of about -100oC followed by a dual step annealing process, the samples were found to be free of dislocation loops, and γ-FeSi2 and β-FeSi2 precipitates coexisting and coherent with the silicon substrate were observed. Photoluminescence (PL) spectra of different line shapes from these implanted samples were observed. By combining the PL and TEM results, the origins of the PL peaks in different samples could be distinguished and identified to be from β-FeSi2 precipitates or from crystal defects in the samples.
INTRODUCTION Ion beam synthesis (IBS) of β-FeSi2 in Si has attracted a lot of research interest in recent years because of its potential in fabrication of Si-based light emitting devices operating at 1.55 µm [1, 2]. However, it is still controversial as whether the 1.55 µm emission from these samples were from β-FeSi2 or from a defect-related emission line (D1) in Si [3]. In this work, FeSi2 precipitates were formed in Si by iron implantation using a metal vapor vacuum arc (MEVVA) ion source and their structures and light emission properties were studied. We shall show that the implantation temperature and annealing conditions played important roles on the shape and phase formation of the FeSi2 precipitates, as well as the formation and distribution of the dislocation loops. At appropriate conditions, a FeSi2 precipitate layer completely free of dislocation loops can be fabricated. In addition, by comparing the photoluminescence (PL) spectra of samples with or without dislocation loops, we can identify the origins of the PL peaks from these samples.
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EXPERIMENTAL DETAILS Iron ions were implanted at an extraction voltage of 40 kV with implantation doses of 5x10 and 3x1016 ions/cm2 into n-type FZ Si (100) wafers with a resistivity of 65~135 Ω-cm using a MEVVA ion source. The implantation was performed at thre
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