Mititaka Terasawa

Characterization of Hard Diamond-Like Carbon Films Formed by Ar Gas Cluster Ion Beam-Assisted Fullerene Deposition

The coordination of carbon atoms in diamond-like carbon (DLC) thin films formed by Ar gas cluster ion beam (GCIB) assisted deposition using fullerene as the carbon source was investigated by measuring near-edge X-ray absorption fine structure (NEXAFS) spectra of the carbon K-edge over the excitation energy range 275–320 eV, using synchrotron radiation. With attention to the peak corresponding to the transition of the excitation electron from a carbon 1s orbital to a π* orbital, relative sp2 contents of various DLC films were estimated. The sp2 contents of the DLC films formed by the GCIB-assisted deposition were observed to be lower than those of the DLC films formed by other methods. The hardness value measured with a nano-indentation technique was found to be strongly related to the sp2 content of the DLC film.

Surface modification of titanium by nitrogen ion implantation

Abstract Nitrogen ions were implanted in high purity titanium at various doses. The nitride phase, TiN, was identified using either grazing incidence X-ray analysis or transmission electron microscopy. AES depth profile of nitrogen was altered from Gaussian-like to a rectangle with increasing nitrogen doses. Both dissolved nitrogen and tendency to form TiN increased precipitates with increasing nitrogen doses. These TiN precipitates that size were several tens of nm were observed at a lower dose. They grew larger as nitrogen dose increased. The dynamic ultra-microhardness rose to a thickness of within 200 nm of the surface owing to TiN formation, resulting in improved wear resistance of titanium. The wear volume was minimum at a dose of 5×10 21 N 2 + m −2 .

Formation of metal–TiN/TiC nanocomposite powders by mechanical alloying and their consolidation

Abstract Fe–TiN, Ni–TiN, and SUS316–TiC nanocomposite powders were prepared by ball-milling Fe–Ti, Ni–Ti, and SUS316–TiC powder mixtures in a nitrogen or argon gas atmosphere. Fe–63vol.% TiN and Ni–44–64vol.% TiN milled powders were dynamically compacted by use of a propellant gun to produce bulk materials of nanocrystalline structure and having grain sizes between about 5 and 400 nm. SUS316–2.8–5.6vol.% TiC milled powders were consolidated by hot isostatic pressing (HIP) to produce bulk materials having grain sizes between about 100 and 400 nm. The possibility of using fine-dispersed TiN/TiC particles to pin grain boundaries and thereby maintain ultra-fine grained structures of grain sizes down to the nanocrystalline scale has been discussed.

Optical Thin Film Formation with O2 Cluster Ion Assisted Deposition

O2 cluster ion assisted deposition was demonstrated to form optical multilayer films for advanced optical communications. With O2 cluster ion assisted deposition, high refractive index 2.20 at 550 nm and very smooth surface (Ra=0.37 nm) of Ta2O5 films were realized. From a scanning electron microscope (SEM) image, dense film structure were observed without porous or columnar structures at the O2 cluster ion assisted layers. The surface and interface of Ta2O5/SiO2 multilayer films were very flat due to surface smoothing effect of cluster ion beams, and it can be realized even though the beneath surface was rough. The shift of a center wavelength of multilayer film was quite small after an environmental test.

Correlative multielectron processes in K-shell photoionization of Ca, Ti and V in the energy range of 8-35 keV

The Kalpha satellite spectra arising from the correlative multielectron processes accompanying K-shell photoionization of Ca, Ti and V were measured using a broad range crystal spectrometer. Multiconfiguration Dirac-Fock calculations were performed to interpret the observed,x-ray energies and the spectral line shape., The calculations agree fairly well with the experimental results. The variation of the KalphaL(1) satellite and the Kalpha(1,2)(h) hypersatellite intensities was measured as a function, of excitation energy in the range of 8-35 keV. The KalphaL(1)/Kalpha(1,2) intensity ratio for each,element is already saturated in our energy range, and the asymptotic values of 1.58 +/- 0.08, 1.26 +/- 0.06 and 0.97 +/- 0.05% for Ca, Ti. and V were determined. By combining the present results and the previously measured values for various elements, we have found a Z(-3.5) scaling law for the KalphaL(1)/Kalpha(1,2) intensity ratio, The measured Kalpha(1,2)(h)/Kalpha(1,2) for each element, is found to increase smoothly from its onset and shows a long saturation range extending up to at least 25 keV above the threshold for Ti. The evolution of the Kalpha(1,2)(h)/Kalpha(1,2) intensity ratio is compared with the analytic Thomas model and with the theoretical calculation based on the screened hydrogenic model. (Less)

High energy resolution PIXE with high efficiency using the heavy ion microbeam

Abstract An X-ray crystal spectrometer using a position sensitive proportional counter combined with tandem microbeam line at Osaka National Research Institute have been developed. This system realizes high energy resolution PIXE analysis using a heavy ion microbeam (E

Flux pinning and flux creep in La2−xSrxCuO4 with splayed columnar defects

The effects of columnar defects with splayed configurations on flux pinning and flux creep were investigated experimentally. Parallel columnar defects and splayed columnar defects were introduced into specimens of La2−xSrxCuO4 by high-energy heavy-ion irradiation. A large enhancement of the flux pinning and the critical current density Jc due to the splayed columnar defects was observed. At temperature T<15 K and a magnetic field H=0.1 T, the effective pinning potential U0 of a specimen with splayed columns was larger than that of a specimen with parallel columns. On the other hand, at 15 K≤T≤30 K and H=0.1 T, U0 of a specimen with splayed columns was smaller than that of a specimen with parallel columns.

ELECTRONIC EXCITATION EFFECTS IN ION-IRRADIATED HIGH-TC SUPERCONDUCTORS

Abstract We have measured the fluence dependence of the c -axis lattice parameter in EuBa 2 Cu 3 O y (EBCO) irradiated with various ions from He to Au over the wide energy range from 0.85 MeV to 3.80 GeV. We have observed a linear increase of the c -axis lattice parameter with increasing fluence for all irradiations. The slope of c -axis lattice parameter against fluence, which corresponds to the defect production rate, is separated into two contributions; the effect via elastic displacement and the effect via electronic excitation. The former contribution exhibits a linear increase against the nuclear stopping power, S n . The latter contribution is scaled by the primary ionization rate, d J /d x , rather than by the electronic stopping power, S e , and is nearly proportional to (d J /d x ) 4 .

Chemical state analysis of Cu, Cu2O and CuO with WDX using an ion microbeam

Abstract The possibility of chemical state analysis with a wavelength-dispersive X-ray spectrometer system for particle-induced X-ray emission (WDX-PIXE) using a light ion microbeam is described. High-resolution Cu Lα 1,2 and Lβ 1 X-ray spectra from Cu, Cu 2 O and CuO targets are measured using this spectrometer system. The incident microbeam is focused 2.0 MeV protons with a beam size of 100(H)×30(V) μm 2 . The Cu L X-ray spectra show two clear main peaks and their satellites. The main peaks are the Lα 1,2 and the Lβ 1 diagram lines, respectively. Due to a high detection efficiency of our spectrometer equipped with a position-sensitive detector for soft X-rays, the intensity ratio Lβ 1 /Lα 1,2 is observable, which is the lowest for pure Cu metal, and the largest for CuO. Moreover, the Lα 1,2 X-ray spectrum for CuO shows a large shoulder at the high energy side of the main peak, which is considered to be due to the chemical bonding between Cu and O atoms. The results show that this system can be used for chemical state analysis for various compound materials and for analyzing small areas of materials or small particles.

High energy resolution PIXE analysis using focused MeV heavy ion beams

Abstract The possibility of chemical state microanalysis using high energy resolution PIXE was investigated using a plane crystal spectrometer installed at a heavy ion microbeam line. The spectrometer has the advantage for the analysis of an X-ray spectrum of simultaneously detecting X-rays over an energy range using position sensitive proportional counter without scanning the crystal. Though the detection efficiency is estimated to be at least four orders of magnitude lower than energy dispersive X-ray spectroscopy (EDS) using a Si(Li) detector, the resolution of the system ( d E E ) is better than 10−3, because the effect of beam size on system resolution is negligible. Focused 2 MeV proton and 5 MeV Si3+ ion beams were employed for the analysis of Si Kα X-rays of Si and SiO2. In both cases, it is possible to detect chemical effects by observing relative intensities of X-ray satellite peaks. However, the use of heavy ions is considered to be more promising because the yields of satellite lines using silicon ion bombardment was much higher than that of protons.