Zn nanoparticles irradiated with swift heavy ions at low fluences: Optically-detected shape elongation induced by nonoverlapping ion tracks

摘要: Elongation of metal nanoparticles (NPs) embedded in silica (SiO{sub 2}) induced by swift heavy-ion (SHI) irradiation, from spheres to spheroids, has been evaluated mainly transmission electron microscopy (TEM) at high fluences, where tens thousands ion tracks were overlapped each other. It is important clarify whether the i.e., track overlaps, are essential for elongation. In this study elongation NPs was low fluences linearly polarized optical absorption spectroscopy. Zn irradiated with 200-MeV Xe{sup 14+} ions an incident angle 45 deg. The fluence ranged 1.0x10{sup 11} 5.0x10{sup 13} Xe/cm{sup 2}, which corresponds coverage ratio (CR) 0.050 25 tracks. A small but certain dichroism observed down 2} (CR = 0.25). comparison numerical simulation suggested that nonoverlapping After further irradiation NP experienced multiple SHI impacts, resulted TEM observation showed elongated whose aspect (AR) 1.2 1.7 2}. Under almost same conditions, Co NPsmore » initial mean radius more prominent AR {approx}4 fluence, while melting point (m.p.) much higher than Zn. Less efficient lower m.p. discussed.« less