Latent ion tracks in amorphous silicon

We present experimental evidence for the formation of ion tracks in amorphous Si induced by swift heavy-ion irradiation. An underlying core-shell structure consistent with remnants of a high-density liquid structure was revealed by small-angle x-ray scattering and molecular dynamics simulations. Ion track dimensions differ for as-implanted and relaxed Si as attributed to differentmicrostructures andmelting temperatures. The identification and characterization of ion tracks in amorphous Si yields new insight into mechanisms of damage formation due to swift heavy-ion irradiation in amorphous semiconductors

Comparative studies using EXAFS and PAC of lattice damage in semiconductors

We have used the perturbed angular correlation (PAC) method and extended X-ray absorption fine structure spectroscopy (EXAFS), along with microscopic methods to investigate the implantation induced disorder and characterize the ion-induced amorphisation of elemental and compound semiconductors

Nanoscale density fluctuations in swift heavy ion irradiated amorphous SiO2

We report on the observation of nanoscale density fluctuations in 2 μm thick amorphous SiO2 layers irradiated with 185 MeV Au ions. At high fluences, in excess of approximately 5 1012 ions=cm², where the surface is completely covered by ion tracks, synchrotron small angle x-ray scattering measurements reveal the existence of a steady state of density fluctuations. In agreement with molecular dynamics simulations, this steady state is consistent with an ion track “annihilation” process, where high-density regions generated in the periphery of new tracks fill in low-density regions located at the center of existing tracks

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

Elongation of metal nanoparticles (NPs) embedded in silica (SiO2) induced by swift heavy-ion (SHI) irradiation, from spheres to spheroids, has been evaluated mainly by transmission electron microscopy (TEM) at high fluences, where tens to thousands of ion tracks were overlapped each other. It is important to clarify whether the high fluences, i.e., track overlaps, are essential for the elongation. In this study the elongation of metal NPs was evaluated at low fluences by linearly polarized optical absorption spectroscopy. Zn NPs embedded in silica were irradiated with 200-MeV Xe14+ ions with an incident angle of 45 degrees. The fluence ranged from 1.0 x 10(11) to 5.0 x 10(13) Xe/cm(2), which corresponds to the track coverage ratio (CR) of 0.050 to 25 by ion tracks. A small but certain dichroism was observed down to 5.0 x 10(11) Xe/cm(2) (CR = 0.25). The comparison with numerical simulation suggested that the elongation of Zn NPs was induced by nonoverlapping ion tracks. After further irradiation each NP experienced multiple SHI impacts, which resulted in further elongation. TEM observation showed the elongated NPs whose aspect ratio (AR) ranged from 1.2 to 1.7 at 5.0 x 10(13) Xe/cm(2). Under almost the same irradiation conditions, Co NPs with the same initial mean radius showed more prominent elongation with AR of similar to 4 at the same fluence, while the melting point (m.p.) of Co is much higher than that of Zn. Less efficient elongation of Zn NPs while lower m.p. is discussed

Shape transformation of Sn nanocrystals induced by swift heavy-ion irradiation and the necessity of a molten ion track

We report on the spherical to rodlike shape transformation of Sn nanocrystals NCs embedded in amorphous SiO2 following irradiation with 185 MeV Au ions. Consistent with previous reports for other metals, transmission electron microscopy demonstrates that under irradiation, Sn NCs larger than a critical size 11 nm elongate parallel to the incident ion direction, while smaller particles remain spherical. Irradiation-induced NC dissolution is significant, as evident from the formation of smaller NCs in place of their original larger counterparts. Using formation conditions that yield Sn NCs at the amorphous-SiO2/crystalline-Si interface, we show that the irradiation-induced shape change occurs only within the SiO2 layer, in the direction opposite to that of the incident ions. We suggest this demonstrates the necessity of a molten ion track and provides further evidence for an elongation process involving NC melting and flow