Low-dose Ion Irradiation Research Articles

Defect-mediated photoluminescence enhancement in ZnO/ITO via MeV Cu++ ion irradiation

Zinc oxide (ZnO) nanowires play a pivotal role in the nanoworld due to their broad range of characteristics and applications. In this work, structural and optical properties of ZnO nanowires grown on indium doped tin oxide (ITO) coated glass have been modified by copper (Cu++) ions irradiation at constant energy of 0.7 MeV. The X-ray diffraction (XRD), photoluminescence (PL), and field emission scanning electron microscope (FESEM) are used to examine changes in the nanowires. XRD results show that the crystallite size first decreases and then increases with high ion dose while peaks’ intensity decreases continuously with increasing the dose. The absence of (102) plane after irradiation depicts the defects formation. FESEM clearly shows the damage that occurred in the density of nanowires and also depicts the reduced charging effect with increasing dose. The PL spectra indicate the strong near-band edge peak and green luminescence enhancement has been recorded due to low dose ion irradiation.

Manipulation of free volumes in a metallic glass through Xe-ion irradiation

The origin of the deformation in metallic glasses is attributed to rearrangements of atoms in some structurally weak spots behaving as flow units, which are associated with free volumes. In the present study, Xe-ion beam is used to manipulate the free-volume fraction, and influence on the mechanical behavior of a Zr-based metallic glass. The irradiation at low dosages can change the structure by increasing the free volume, and by homogenising the distribution of free volume. The increase in the free-volume fraction is equivalent to the increase in the deformation temperature, thus resulting in the decrease in the yield strength. The analysis of stochastic strain burst size in the metallic glass irradiated at different dosages indicates that the strain burst depends on the yield strength and homogeneity of the glassy phase. The results of this study highlight the fact that the quantitative manipulation of the homogeneity and the amount of free volumes can be achieved through low-dose ion irradiation, which can modify the mechanical behavior of metallic glasses.

Irradiation response of commercial, high-Tc superconducting tapes: Electromagnetic transport properties

Effects of low dose ion irradiation on the electrical transport current properties of commercially available high-temperature superconducting, coated-conductor tapes were investigated, in view of potential applications in irradiative environments. Three different tapes, each with unique and tailored as-grown flux-pinning structures, were irradiated with Au and Ni ions at energies that provide a range of damage effects, with accumulated damage levels near that expected for conductors in, for example, a fusion reactor environment. Measurements using transport current determined the pre- and post-irradiation resistivity, critical current density, and pinning force density, yielding critical temperatures, irreversibility lines, and inferred vortex creep rates. Results show that, at the irradiation damage levels tested, any detriment to as-grown pre-irradiation properties is modest; indeed in one case already-superior pinning forces are enhanced, leading to higher critical currents.

Recent Progress of Ion Irradiation Bit Patterned Media

Recent progress of the bit patterned media fabricated by ion irradiation method is reviewed. High energy ion irradiation is a useful method to modify the magnetic properties and this technique can be used to fabricate high density bit patterned media which is a promising candidate to overcome the limit of the areal density of the conventional recording media. In order to achieve magnetic patterned structure having the feature size less than 50 nm by the ion irradiation technique, the materials whose magnetic order is easily suppressed by low dose ion irradiation are necessary. One of the candidate is L12 phase CrPt3, and the control of the magnetic order of CrPt3 by the ion irradiation and the fabrication of CrPt3 bit patterned medium are discussed.

Influence of low dose ion irradiation on the structure and physical–mechanical properties of solids

This paper studies the laws of plastic deformation due to irradiation by continuous and pulsed flows of ions in the interval of small doses 10 13–10 15 cm −2. Also investigated are the influence of irradiation within the above-shown interval on texture and on the physical–mechanical properties of thin films and bulk specimens of metal and alloys.

Disordering kinetics of Ni 3Al under ion irradiation

The stability of the long-range-ordered (LRO) γ′ phase was investigated in the temperature interval 100 K ⩽ T⩽773 K under 300 keV Ni + irradiation. The radiation-induced intensity changes of the L1 2 superlattice reflections were monitored by TEM technique using a computer assisted, quantitative evaluation of the amplitudes of diffraction patterns obtained by image plates. The dynamical diffraction theory where the thickness of the investigated foils was taken into account was employed to determine the degree of order from the diffraction patterns. The fluences were varied up to 10 dpa. The results are compared with recent measurements of disordered zone sizes after low dose ion irradiation in Ni 3Al. The measured temperature dependence below room temperature is consistent with the predictions of the thermal spike model for disordering, but for higher temperatures the results hint to a more complicated re-ordering process in disordered areas. A Ni 3Al specimen which was completely disordered after 10 dpa at 200 K was used for a thermal annealing experiment. The annealing behavior confirms the importance of the heterogeneous state of the order for the re-ordering process under ion irradiation.

Disordering in the Ni-Al system under low dose ion-irradiation: a computer simulation study

ABSTRACTStarting from the radiation damage cascades, as obtained using the binary collision approximation, we derive the spatial distribution of the energy deposited into the lattice by the primary knock-on atom (PKA). We follow the time evolution of the cascade core in two ordered intermetallics Ni3Al and NiAl, using the molecular dynamics (MD) method with the embedded potential and with the liquid droplet model (LDM) in which a simplified version of the heat equation is solved. Moreover, the MD was used to determine the evolution of the local structure and to identify the disordered zones. The LDM allows us, after a calibration with MD results, to estimate the dependence of the molten volume on the PKA energy up to 1 MeV. The results show good agreement with other published simulations and the available transmission electron microscopy (TEM) observation experiments.

Derelaxation of Amorphous Silicon by Ion Implantation: Optical Characterization

ABSTRACTThe transition between relaxed and unrelaxed amorphous silicon can be obtained by thermal treatment of the unrelaxed amorphous or by low dose ion irradiation of the relaxed material. In both cases a variation in the short range order has been invoked to explain the behavior of the structural changes probed by various techniques. In this work we study the influence of such changes on the optical properties of a-Si in the region of the transition between the relaxed and the unrelaxed states. We show that a progressive variation of the optical constant in the visible-near infrared region upon derelaxation occurs. Therefore, significant modifications of the electron density of state in the region above the optical gap are associated with the changes in the short range order probed by Raman spectroscopy.