Irradiation Ion Fluence Research Articles

Effect of irradiating ion fluence on optical properties of ZnO1−x:Nx thin films

Swift heavy ion (SHI) irradiation is an effective technique to modify the optical properties of the materials. In the present investigation, the effect of 100 MeV Ag7+ SHI irradiation fluence on the optical properties of ZnO1−x:Nx thin films was studied. The post irradiation spectroscopic characterizations such as UV–VIS reflectance spectroscopy, Raman spectroscopy and photoluminescence (PL) spectroscopy analysis were carried out. The studies imply that when the SHI passes through the solid, the higher electronic stopping power of ions can weaken oxygen bonds in ZnO, resulting in the formation of donor defects such as oxygen vacancies and zinc interstitials. The formation of donor defects has been acknowledged through the increase in bandgap with irradiating ion fluence. The blue shift observed from the Raman spectra for the 3 × 1013 ions/cm2 fluence-irradiated films implies the existence of compressive stress in the films. The PL analysis acknowledges the formation of donor defects upon irradiation. Furthermore, it conveys that the presence of N atoms in ZnO lattice leads to the formation of a less number of defects as compared with undoped ZnO while irradiation.

Surface and interface modification of Zr/SiC interface by swift heavy ion irradiation

In this study thin Zr films (135nm) were deposited on 6H-SiC substrate at room temperature by sputter deposition. The Zr/SiC couples were irradiated by 167MeV Xe26+ ions at room temperature at fluences of 5.0×1012, 1.0×1013, 5.0×1013, 2.0×1014, 3.1×1014 and 6.3×1014ions/cm2. The samples were analysed before and after irradiation using Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM) and secondary electron microscopy (SEM). The surface morphology from SEM analysis revealed a homogeneous Zr surface which did not vary with increasing fluences of irradiation. AFM analysis revealed that the Rrms surface roughness did increase from the as-deposited value of 1.6nm and then decrease at higher SHI irradiation fluences to 1.4nm. RBS results indicate that interface mixing between Zr and SiC interface occurred and varied linearly with irradiation ion fluence. The value obtained for diffusivity of Zr shows that the mixing was due to interdiffusion across the interface during a transient melt phase according to the thermal spike model.

Magnetic patterning of FeRh thin films by energetic light ion microbeam irradiation

Magnetic patterning of FeRh thin films of various shapes and dimensions by 2 MeV H and He ion microbeam irradiation was examined by X-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM) at the photon energy of the Fe L3 absorption edge. The XMCD-PEEM images clearly show that the various magnetic patterns whose sizes are about 1–2 µm, can be successfully produced by controlling the scan condition and the size of the ion beam probe. Furthermore, the quantitative analysis of the XMCD-PEEM images reveals that the localized magnetization in the micrometer-sized magnetic patterns significantly depends on the irradiation ion fluence. In addition, the annealing condition is also found to be one of the predominant factors that determine the magnetic state even for the micrometer-sized magnetic patterns.

Change in magnetic and structural properties of FeRh thin films by gold cluster ion beam irradiation with the energy of 1.67 MeV/atom

The effect of energetic cluster ion beam irradiation on magnetic and structural properties of FeRh thin films have been investigated. The cluster ions used in the present studies consist of a few gold atoms with the energy of 1.67 MeV/gold atom. Saturation magnetization of the sample irradiated with Au3 cluster ion beam (280 emu/cc) is larger than that for the irradiated sample with Au1 ion beam (240 emu/cc) for the same irradiation ion fluence. These results can also be confirmed by the X-ray magnetic circular dichroism (XMCD) measurement; the XMCD signal for Au3 cluster ion irradiation is larger than that for Au1 ion irradiation. Since the ion beam irradiation induced magnetization of FeRh is significantly correlated with the amount of the lattice defects in the samples, cluster ion beam irradiation can be considered to effectively introduce the lattice defects in B2-type FeRh rather than the single ion beam. Consequently, cluster ion irradiation is better than single ion irradiation for the viewpoint of saturation magnetization, even if the same irradiation energy is deposited in the samples.

Study on ferromagnetic ordering of FeRh thin films induced by energetic heavy ion irradiation by means of X-ray Magnetic Circular Dichroism

We investigated the ion irradiation induced ferromagnetic state of FeRh thin films with 10MeV I ion beam by the measurements of a superconducting quantum interference device (SQUID) magnetometer as well as of soft X-ray Magnetic Circular Dichroism (XMCD). It was clearly shown in the magnetization loops by SQUID measurements that the ion irradiation induced the ferromagnetic state in the FeRh thin films even below room temperature. This was also confirmed by the Fe L2,3-edge XMCD measurements for the irradiated FeRh film samples. However, we found that the irradiation ion fluence dependence on the magnetization was totally different between two measurement techniques. We also revealed by XMCD sum rule analysis that the ferromagnetism in the ion irradiated FeRh thin films was mainly dominated by the spin moment.

Fabrication of complex curved three-dimensional silicon microstructures using ion irradiation

We have developed a process to fabricate arbitrary-shaped, three-dimensional microstructures in 0.4 Ω cm p-type silicon using focused high-energy proton beam irradiation, followed by electrochemical anodization. This has enabled us to produce free-standing complex microstructures such as arrays or long wires, grids, wheels, vertically stacked wires and wires which can be controllably bent upward and downward in the vertical plane. The two most important factors which determine the wire cross-section dimensions and depth are the irradiation ion fluence and energy. We can controllably vary the width of wires from 1 to 5 µm by varying the fluence of 1 MeV protons and the depth of wires from 2 to 15 µm by varying the proton energy. By using a combination of multiple energy proton irradiation over a range of 200–1000 keV, and gray-scale masks, different ion penetration depths and multilevel free-standing three-dimensional silicon structures can be obtained in a single etch step.

Far-action radiation defects and gettering effects in 6H-SiC irradiated with Bi ions

We report on cathodeluminescence study of radiation defects in silicon carbide implanted by heavy ions of Bi at high energy. Irradiated and annealed samples were measured to investigate radiation defects distribution variation with fluence. It is shown that diffusion and gettering effects are occurred during irradiation. The data show that defect distribution depend on irradiation ion fluence drastically.

Surface modification of polymers by ion-assisted reaction

This paper deals with a new surface modification technique of polymers, the so-called ion-assisted reaction (IAR) to improve the surface properties of polymers and provides outstanding experimental results regarding wettability and adhesion of various polymers. In the IAR, polymer surfaces were subjected to low energy ion irradiation at different dosage in reactive gas environment. Dramatic improvements in wettability and surface energy are observed for the IAR-treated polymer surfaces and can be explained by the addition of functional groups, responsible for the increase of polar component in surface energy. The formation of functional groups results from the interaction among ion, reactive gas and polymer chain involved in IAR treatment, depending on the reactive ion species, the flow rate of the reactive gas and the irradiating ion fluence. The improvement in adhesion between the IAR-treated polymers and coating materials was explained in terms of the increased surface energy as well as surface roughness in the polymers modified by the IAR and possible adhesion enhancement mechanism is to be discussed.

Ion beam assisted formation of Ag nanoparticles in SiO 2 and their optical properties

Ag nanoclusters in SiO 2 matrix were formed by magnetron co-sputtering followed by ion irradiation. The refractive index and optical extinction spectra of the films were studied. The SiO 2:Ag thin films exhibit a plasmon resonance in the visible region. In the as-deposited films the Ag nanoclusters are less then 0.5 nm in size. The intensity of the plasmon peak is low. After irradiation with 4.5 MeV Au ions the intensity of the peak increases and it becomes narrower. The FWHM of the plasmon peak corresponds to a mean radius increasing with the ion fluence. The method of the disappearing diffraction pattern was used for the refractive index determination. It is a critical angle method and is applicable for measurements of layers with thickness comparable with the used wavelength. Moreover it is insensitive to surface gradients of the real part of the refractive index and roughness, which disturb elipsometric data. The refractive index enhances with the increasing Ag concentration and irradiation ion fluence, as is expected from the light scattering theory.

Swift heavy ion irradiation induced luminescence from C-doped SiO 2 films

In the present work, a novel technique, “low energy ion implantation+high-energy heavy ion irradiation”, was used to synthesis light-emitting material. Experimentally, thermal-grown SiO 2 films were firstly implanted with 120 keV C + ions at room temperature (RT) to total doses in the range of (5.0×10 16–1.0×10 18) ions/cm 2. These C-doped SiO 2 films were then irradiated at RT with 335 and 855 MeV 40Ar or 1.98 GeV 84Kr ions to a fluence of 1.0×10 12 ions/cm 2, or with 1.75 GeV 136Xe ions to 1×10 11, 5×10 11 or 1×10 12 ions/cm 2, respectively. By measuring photoluminescence (PL) spectra of these samples excited by 320 nm light, the PL bands were investigated as functions of implantation ion dose, irradiation ion fluence and electronic energy loss S e. It was found that this technique is a useful tool to produce high quality light-emission structures, and that high-energy heavy ion irradiated C-doped SiO 2 films should be an efficient blue–violet emitting material. Furthermore, S e plays a dominant role in the formation of the PL bands, and proper C-dopant and suitable irradiation fluence will enhance the PL efficiency. Possible origins of the blue-violet PL bands formed in the ion irradiated C-doped SiO 2 films were discussed.

Creep of a crystalline metallic layer induced by high energy heavy ion irradiation

The atomic transport induced by ion electronic energy loss in amorphous systems is studied on metallic sandwiches irradiated at liquid nitrogen temperature with 500 MeV iodide ions delivered by the VICKSI accelerator of the Hahn-Meitner-Institut (Berlin). The sandwiches are composed of two amorphous Ni3B layers of 1 or 1.5 μm thickness embedding a crystalline Au or W layer of thickness varying from 20 to 900 nm. Rutherford backscattering experiments using a 3.6 MeV He2+ beam delivered by the ARAMIS accelerator of the CSNSM (Orsay) were performed in order to determine the modifications of the geometry of the sandwiches after swift heavy ion irradiation. The results show a huge creep of the crystalline part of the sandwiches. The magnitude of this creep depends on the nature of the crystalline layer (Au or W) and increases steadily with the irradiating ion fluence with a strain-rate decreasing with increasing layer thickness. This creep phenomenon is due to the plastic deformation process occurring in the surrounding amorphous layers and is induced by ion electronic energy loss. A simple rheological model is developed to reproduce the observed effects.