Departmental Seminar

National Institute for Materials Science, Tsukuba, Japan

Dr Hiroshi Amekura
Tuesday 28 February 2012 11am–12.30pm
RSPE Link Seminar Room

Dr Hiroshi Amekura

National Institute for Materials Science, Tsukuba, Japan

“Modifications of Metal Nanoparticles in SiO2by Ion Irradiation: Elongation, Amorphization

Metal nanoparticles embedded in a transparent insulator have various possible applications, e.g., ultrafast
optical switches, single electron transistors, super-high density recording media, etc. Some properties of the
metal particle system can be modified by ion irradiation via shape elongation and amorphization of
nanoparticles. In this talk, two different ion irradiation effects on metal nanoparticles will be presented.
(1) Elongation of metal nanoparticles induced by swift heavy ion irradiation
in 2003, a French group irradiated cobalt nanoparticles in SiO2 with swift heavy ions (SHI) of 200 MeV
iodine, and observed shape changes of the nanoparticles from spherical to elongated shape and finally to
nanorods with increasing the fluence [1]. While the mechanism is still under debate, one of the most wellrecognized
one is a synergy effect between in-plane stress due to the ion hammering effect and transient
melting of metal nanoparticles by thermal spike effect. Recently we have carried out SHI irradiation to two
different species of metal nanoparticles, i.e., Zn [2] and V [3], which have bulk melting points of 420 and
1890°C, respectively. If the melting of the nanoparticles was involved in the elongation mechanism, a large
difference in the elongation could be observed between them because of the large difference in the melting
points. However, we observed almost the same degree of the elongation in both Zn and V nanoparticles.
The results are discussed in the talk.
(2) Amorphization of metal nanoparticles induced by MeV heavy ion irradiation
In 2007, an Australian group has succeeded in amorphization of Cu nanoparticles in SiO2 by irradiation with
6 MeV Sn3+ ions at liquid nitrogen temperature [4]. Here, we reports changes of optical absorption,
particularly of the surface plasmon resonance peak, induced by the amorphization [5].
[1] C. D’Orléans, et al., Phys. Rev. B 67, 220101 (2003).
[2] H. Amekura, et al., Phys. Rev. B 83, 205401 (2011).
[3] H. Amekura, et al. Nucl. Instrum. Methods Phys. Res. B 269, 2730 (2011).
[4] B. Johannessen, et al., Phys. Rev. B 76, 184203 (2007).
[5] H. Amekura, B. Johannessen, et al., Appl. Phys. Lett. 99, 043102 (2011).
Dr Hiroshi AMEKURA is a Chief Researcher of the Quantum Beam Unit, National Institute for Materials
Science (NIMS), Tsukuba, Japan. He has received MS (solid state physics) from Univ. of Tokyo in 1991,
PhD (materials science) from Univ. of Tsukuba in 1999. Since he has joined NIMS in 1991, he is working in
researches on phenomena related with ion beams; radiation-induced conductivity, radiation damage, rareearth
ion implantation doping, high-flux implantation, beam-solid interaction, etc. His recent interest covers
fabrication and modification of metal and oxide nanoparticles by ion beams, and characterization of novel
properties of the nanoparticles.


Ms Helen Shelper

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