Thermal stability of embedded metal nanoparticles elongated by swift heavy ion irradiation: Zn nanoparticles in a molten state but preserving elongated shapes

摘要: Solid Zn and V nanoparticles (NPs) embedded in silica were elongated by swift heavy ion (SHI) irradiation with 200 MeV Xe14+ ions to a fluence of 5.0 × 1013 ions cm−2. Isochronal annealing was carried out vacuum from 200 1000 °C steps 100 °C for 10 min each. The degree shape elongation evaluated at room temperature (RT) two different optical methods: linear dichroism spectroscopy birefringence spectroscopy. In the as-irradiated state, samples showed an absorption band 5 eV due radiation-induced defects addition anisotropic metal NPs. After 400 °C defect had completely disappeared, while almost unchanged or rather slightly increased both NPs decreased but maintained certain value after 500 °C, which is much higher than melting point (MP) (∼420 °C). This observation indicates that mostly even if are molten state some extent during annealing. eliminated 600 °C. case NPs, up 800 °C 900 °C. Since recovery 900 °C spherical lower MP bulk (1890 °C), we consider without i.e. via solid mass transportation. not key factor shape.