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Journal of Electron Microscopy 48(4): 399-405 (1999)
© 1999 Oxford University Press
In-situ observation of the microstructural evolution in germanium under the low-energy helium ion irradiation
Department of Material Science, Interdisciplinary Faculty of Science and Engineering, Shimane University 1060 Nishikawatsu, Matsue 690-8504
1Origin Electric Co., Ltd 1-18-1 Takada, Toshima-ku, Tokyo 171, Japan.E-mail: arakawak{at}ifsel.riko.shimane-u.ac.jp
Effects of helium atoms on the defect clustering in germanium are examined by irradiation with low-energy helium ions, using a specially designed transmission electron microscope which is connected with an ion accelerator. Dynamic microstructure evolution under low-energy (10 keV) helium ion irradiation with a beam flux of 7.0×1016 ions m2 s1 is observed at various temperatures between 85 and 870 K. Under around 290 K, a number of small defects (<6 nm in the diameter) are formed, which are probably of vacancy-helium complex and the precursor of (001) lenticular helium bubbles. At about 290-670 K, interstitial-type defects lying on {113} planes are mainly produced which grow to form perfect dislocation loops under the irradiation. The features of the {113} defects introduced under the low-energy helium ion irradiation are compared with those formed by electron irradiation. The enhanced formation of {113} interstitial-type defects and the extensive width of the defects under the irradiation of helium ions above 290 K imply the mechanism of helium cutting saturated bonds between germanium atoms.
Keywords lattice defect, radiation effect, germanium, helium, ion irradiation, electron microscopy
Received 30 November 1998, accepted 8 January 1999