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Morphology changes on various metals by helium irradiation are shown experimentally. It has been revealed that a whisker-like nanostructure was formed on tungsten and molybdenum surfaces by the exposure to a helium plasma. After helium irradiation to titanium and stainless steel, many dots in several hundreds of nanometers cover the surface. The morphology change may be caused by the growing process of helium bubbles in the sub-surface region.
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Kajita et al. (2011) studied this question.
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