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Irradiation Temperature Dependence of Shape Elongation of Metal Nanoparticles in Silica: Counterevidence to Ion Hammering Related Scenario
Irradiation temperature (IT) dependence of the elongation efficiency of vanadium nanoparticles (NPs) in SiO2 was evaluated: The samples were irradiated with 120 MeV Ag^9+ ions to a fluence 1.0 X 10^14 ions/cm2 at each IT between 300 K and 591 K, while the measurements were performed at room temperature. The vanadium was selected for the NP species because of the highest bulk m.p. of 1890 C among all the species of the elemental metal NPs in which the shape elongation was observed. The highest m.p. could contribute negligible size changes of NPs against inevita-ble exposure to high temperatures for the IT dependence measurements. The elongation of V NPs was evaluated qualitatively by transmission electron microscopy (TEM) and quantitatively by the optical linear dichroism (OLD) spectroscopy. The electron microscopy studies showed a pronounce elongation of NPs with SHI irradiation at the elevated temperatures. The OLD signal was almost constant, or even slightly increased with increasing the IT from 300 K to 591 K. This IT dependence provides a striking contrast to that of the ion hammering (IH) effect, which pre-dicts a steep decrease with increasing IT. Combined with other two counterevidence previously reported, the IH-related effect is excluded from the origin of the shape elongation of metal NPs in SiO2.
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- 07/04/2023
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