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The irradiation damage behaviors of single crystal (SC), coarse-grained (CG), and nanograined (NG) copper (Cu) films were investigated under Helium (He) ion implantation at 450 °C with different ion fluences. In irradiated SC films, plenty of cavities are nucleated, and some of them preferentially formed on growth defects or dislocation lines. In the irradiated CG Cu, cavities formed both in grain interior and along grain boundaries; obvious void-denuded zones can be identified near grain boundaries. In contrast, irradiation-induced cavities in NG Cu were observed mainly gathering along grain boundaries with much less cavities in the grain interiors. The grains in irradiated NG Cu are significantly coarsened. The number density and average radius of cavities in NG Cu was smaller than that in irradiated SC Cu and CG Cu. These experiments indicate that grain boundaries are efficient sinks for irradiation-induced vacancies and highlight the important role of reducing grain size in suppressing radiation-induced void swelling. [ABSTRACT FROM AUTHOR]

We have explored the capacity of Cu/V interfaces to absorb helium ion radiation-induced defects spanning a peak damage range of 0.6–18 displacements per atom (dpa). The study provides evidence of alleviated nucleation of He bubbles in the multilayer films from Cu/V 50 nm to Cu/V 2.5  nm. Layer interfaces are retained in all irradiated specimens. Peak bubble density increases monotonically with fluence, and is lower in multilayers with smaller individual layer thickness. Radiation hardening decreases with decreasing layer thickness and appears to reach saturation upon peak radiation damage of 6 dpa. Size- and fluence-dependent radiation damage in multilayers is discussed. [ABSTRACT FROM AUTHOR]

The microstructural evolution of Ne-ion-irradiated anatase TiO2/SrTiO3 films was investigated. A defect denuded layer formed in the TiO2 film near the TiO2/SrTiO3 interface after irradiation. The accumulation of defects at the TiO2/SrTiO3 interface led to the formation of a continuous interfacial amorphous layer on SrTiO3. Both observations are attributed to the interaction of defects with the interface. Present results reveal that a hetero-epitaxial interface between two different oxides can act as an effective sink to absorb irradiation-induced defects. [Copyright &y& Elsevier]

We have shown that 1MeV Ni+ ion irradiation can cause nanocrystal formation in Ni52.5Nb10Zr15Ti15Pt7.5 metallic glass (MG). The process requires precipitate formation and subsequent crystal growth within the precipitates. Temperature evolution modeling of damage cascades suggests a locally melted region within the damage cascade with substantial temperature gradients and rapid energy dissipation, with a quenching rate much larger than MG’s critical cooling rate. Thus, the damage cascade regions do not directly develop nanocrystals. [ABSTRACT FROM AUTHOR]

Abstract: We have systematically studied Ar-ion-milling-induced microstructural evolution in Cu50Zr45Ti5 metallic glass (MG) during specimen preparation for transmission electron microscopy (TEM). We have observed the formation of a Cu10Zr7 intermetallic phase in samples prepared using low energy ion milling (2keV) but without evident crystallization. We also observed the formation of nanocrystalline Cu10Zr7 phase (with a possibility of being mixed with other minor phases) in samples prepared using high energy ion milling (⩾3keV). In contrast, the MG samples remained in the glassy state without any microstructural changes when prepared by either electropolishing or low energy ion milling with liquid nitrogen cooling (2keV). Further, our study suggests that chemical decomposition might be a necessary intermediate stage for crystallization. In situ TEM electron irradiation shows ion-milling-induced phase segregation and preferred nanocrystallization in the precipitated regions. [Copyright &y& Elsevier]

Abstract: Ion irradiation can be used to induce partial crystallization in metallic glasses to improve their surface properties. We investigated the microstructural changes in ribbon Zr55Cu30Al10Ni5 metallic glass after 1MeV Cu-ion irradiation at room temperature, to a fluence of 1.0×1016 cm−2. In contrast to a recent report by others that there was no irradiation induced crystallization in the same alloy [S. Nagata, S. Higashi, B. Tsuchiya, K. Toh, T. Shikama, K. Takahiro, K. Ozaki, K. Kawatusra, S. Yamamoto, A. Inouye, Nucl. Instr. and Meth. B 257 (2007) 420], we have observed nanocrystals in the as-irradiated samples. Two groups of nanocrystals, one with diameters of 5–10nm and another with diameters of 50–100nm are observed by using high resolution transmission electron microscopy. Experimentally measured planar spacings (d-values) agree with the expectations for Cu10Zr7, NiZr2 and CuZr2 phases. We further discussed the possibility to form a substitutional intermetallic (Ni x Cu1− x )Zr2 phase. [Copyright &y& Elsevier]

We studied the role of thermal spike in nanocrystallization of Cu50Zr45Ti5 metallic glasses after 1MeV Cu ion irradiation at room temperature. Nanocrystals of Cu10Zr7 and CuZr2 phases are formed after the ion irradiation. The study suggests that thermal spike formation and subsequent quenching are too fast to allow direct structural transformation in the damage cascade regions. The overall irradiation effects are caused by enhanced atomic mobility due to increased excessive free volume. [Copyright &y& Elsevier]

Abstract: We report on the evolution of microstructure and mechanical properties of Fe/W multilayers subjected to helium ion irradiations. Sputtered Fe/W multilayers with individual layer thickness, varying from 1 to 200nm, were subjected to He+ ion irradiation with a peak displacement per atom value of 6 at ambient temperatures. Helium bubbles, 1–2nm in diameter, were observed in Fe and W, and more so along layer interfaces. The magnitude of hardness variation after radiation depends on the individual layer thickness. Radiation hardening is observed in specimens with individual layer thickness of ⩾5nm. At smaller layer thickness, the hardness barely changes. Analysis indicates that radiation hardening may originate mainly from dislocation loops and partially from He bubbles. [Copyright &y& Elsevier]

Abstract: Application of metallic glasses as structural materials has been limited by their poor ductility. To overcome brittle failure, nanocrystals are intentionally introduced to stabilize the glasses. In this study, we report on the application of ion irradiation to induce nanocrystalization in a Cu50Zr45Ti5 (CZT) alloy. Transmission electron microcopy, microindentation and nanoindentation have been used to characterize the CZT alloy irradiated with 140keV He ions at room temperature. Hardness enhancement was observed near the projected range of the He ions, coinciding with the formation of nanocrystals. Such microstructural changes, however, were not observed in the near surface region, where the electronic stopping process is dominant. [Copyright &y& Elsevier]

Abstract: We have investigated the evolution of radiation damage and changes in hardness of sputter-deposited Cu/V nanolaminates upon room temperature helium ion irradiation. As the individual layer thickness decreases from 200 to 5nm, helium bubble density and radiation hardening both decrease. The magnitude of radiation hardening becomes negligible for individual layer thickness of 2.5nm or less. These observations indicate that nearly immiscible Cu/V interface can effectively absorb radiation-induced point defects and reduce their concentrations. [Copyright &y& Elsevier]

Abstract: Highly epitaxial thin films of YBa2Cu3O y (YBCO) have been grown on silicon with a double buffer of Eu2CuO4(ECO)/Y-ZrO2(YSZ). The utilization of the ECO layer, which possesses a very stable 214-T'' structure and excellent compatibility with YBCO, greatly improves the epitaxy and surface morphology of the grown YBCO film, whereas the YSZ layer efficiently blocks the interaction between silicon substrate and YBCO. The grown films were characterized by grazing incidence X-ray reflection, rocking scans of the X-ray diffraction peaks, scanning electron microscopy, cross-sectional transmission electron microscopy, and surface profilometry. The results showed an enhanced crystallinity and very clear interfaces between layers, demonstrating the advantages of such an ECO/YSZ double buffer. It was also found that this bi-layer buffer structure could greatly improve the surface roughness of the YBCO films. [Copyright &y& Elsevier]

The irradiation response of metallic glass Ni 50 Nb 10 Zr 15 Ti 15 Pt 7.5 Cu 2.5 under 3 MeV Au ion irradiation was studied. Significant hardness decrease was observed under low dose irradiation. However, the hardness restores to the level of unirradiated sample under higher dose irradiation. Positron annihilation Doppler broadening results indicate that ion bombardment would destroy the short range order (SRO) in metallic glass and introduce excessive free volume under low dose irradiation. While the formation of local ordered structure would consume the free volume due to enhanced atom mobility under higher dose irradiation. Our results help to understand the mechanism of the irradiation effect in metallic glass, and moderate ion radiation can be an efficient way to improve the mechanical property of metallic glass by introducing free volume in metallic glass. [ABSTRACT FROM AUTHOR]

Sputtering-deposited Cu/V multilayer films with the individual layer thickness varying from 2.5 nm to 100 nm were irradiated by 1 MeV helium (He) ion at the fluence of 6 × 10 16 ions · cm - 2 at room temperature. The resistivity of Cu/V multilayer films after ion irradiation was evaluated as a function of individual layer thickness at 300 K and compared with their resistivity before ion irradiation. The results show that the resistivity change before and after ion irradiation is largely determined by the interface structure, grain boundary and radiation induced defects. A model amended based on the model used in describing the resistivity of as-deposited Cu/V multilayer films was proposed to describe the resistivity of ion irradiated Cu/V multilayer films by considering the point defects induced by ion irradiation, the effect of interface absorption on defects and the effect of interface microstructure in the multilayer films. [ABSTRACT FROM AUTHOR]