Construction of superconducting bulk magnet magnetron sputtering apparatus for fabrication of highly reflective optical mirrors

We have developed the two-cathode magnetron sputtering apparatus equipped with superconducting permanent magnet to produce Mo/Si multi-layer films, which would potentially serve as a high-quality optical mirror at extreme ultraviolet (EUV) wavelength of 13.5 nm. The best deposition condition was searched by analyzing the structure of the inter-diffusion layer formed in the Mo/Si bi-layer film prepared under different deposition conditions. It was found that (1) Xe gas should be used as inert gas species, (2) its pressure is lower than 4 × 10⁻² Pa, (3) a throw distance is longer than 250 mm and (4) discharge voltage around 2 kV. By making full use of these data, we synthesized Mo/Si multi-layer films and analyzed the structure and its effect on the reflectivity. The highest EUV-reflectivity so far obtained is 67% in the normal incident condition.     

PIXE analysis of biological bodies in Uranouchi bay

We have investigated shellfish called Japanese littleneck clam (Ruditapes philippinarum) which were collected from Uranouchi bay (Kochi, Japan) for analysis of elemental concentration by Particle Induced X-ray Emission (PIXE). A 4 MeV He⁺⁺ ion beam was used to analyze shellfish in the ion beam laboratory of Kochi University of Technology (Japan). In the present study, shellfish have been chosen as a representative of the biological bodies in the Uranouchi bay. The concentration of heavy metals in shellfish has been quantified and the results are compared with those obtained by analyzing Market shellfish. Analyzing shellfish collected from three different places in the bay Cu, Zn, Br, Sr and Zr are detected as heavy metals. Our results suggest that in comparison with Market shellfish the Uranouchi bay shellfish contain more heavy metals.     

Relation between the size of motor units and the spectral characteristics of their action potentials. kazuseki@iname.com

Cis and trans isomers of two dinuclear platinum complexes, [cis-?Pt(NH3)2Cl?2 mu-(NH2(CH2)nNH2)](NO3)2 (1,1/c,c) and [trans-?Pt(NH3)2Cl?2 mu-(NH2(CH2)nNH2)](NO3)2 (1,1/t,t), where the diamine was 1,4-butanediamine (n = 4) or 1,6-hexanediamine (n = 6), were studied using electrospray ionization surface-induced dissociation (ESI/SID) tandem mass spectrometry (MS/MS). The same fragment ions were observed for both the cis and trans isomers of each complex (n = 4 or 6), but the relative intensities were dependent on the isomer studied. The ESI/SID data and energy-resolved mass spectra show that the position of the chloride plays a significant role in the fragmentation of these ions. Two major fragmentation pathways were detected for the complexes. The cleavage of the Pt-N bond trans to chloride was the most favorable pathway for both isomers of the complexes following the ion-surface collision. The differences in the ESI/SID spectra between the cis and trans isomers can be explained by the trans effect, namely that the Pt-N bond trans to chloride is the most labile bond.     

Formation of thick titanium carbide films by the hollow cathode discharge reactive deposition process

Thick titanium carbide films were successfully deposited on mild steel sheets using a hollow cathode discharge reactive deposition process. Methane, ethylene and acetylene were used as reactant gases during the titanium evaporation and the substrates were either negatively biased or grounded. The deposited films were characterized by microhardness measurements, X-ray diffraction, Auger electron spectroscopy and secondary ion mass spectrometry. The results are discussed with regard to deposition conditions and chemical composition.     

Development of micro-beam NRA for 3D-mapping of hydrogen distribution in solids: Application of tapered glass capillary to 6 MeV N ion

A micro-beam NRA system, by means of a resonant nuclear reaction ¹H(¹⁵N, αγ)¹²C, has been developed for the purpose of the 3D mapping of the hydrogen distribution in solids. To obtain the tens μm size of the beam spot, the combination of the newly proposed tapered glass capillary and a conventional quadrupole magnetic lens is employed. An Y patterned film on a substrate is prepared as an application of the developed system. The 6 MeV ¹⁵N beam focused by glass capillaries down to 50 μm successfully shows the hydrogen distribution. The in-plane NRA profile implies that the beam emitted from the glass capillary outlet is parallel, although the original beam has a considerable divergence. The NRA measurements in the 10³ Pa N₂ atmosphere due to the low gas conductance of the glass capillary is also demonstrated.     

RBS study of Ti/ZnO interface

We have studied the interface stability of the Ti(overlayer)/ZnO(substrate) system. Ti thin film was grown on the Zn face of single crystal ZnO(0 0 0 1) substrate by the vacuum deposition technique. The Ti film thickness was typically 16 nm. Then the samples were annealed in air at 300 and 400 °C for 15 min, respectively. The deposition and annealing effects on the interface structure were investigated with Rutherford backscattering and channeling spectroscopy using 2 MeV He⁺ ion beam. After Ti deposition the minimum yield from the ZnO substrate increased from 2% to 7%. This suggests severe damage caused by deposition, i.e. the interface reaction between Ti and ZnO (even at room temperature). A significant amount of Zn (approximately 6.4 × 10¹⁶ atoms/cm²) moved onto the surface after post-annealing at 400 °C. Since Ti has a stronger tendency to react with O than Zn, it is expected that Ti reacts with substrate oxygen leaving behind free Zn atoms, which can easily migrate onto the surface. We discuss how the Ti/ZnO interface reaction in detail, and seek to find another good metallic contact for ZnO devices, which are attracting much attention recently for practical applications as well as scientific aspects.     

Application of swift and heavy ion implantation to the formation of chalcogenide glass optical waveguides

We demonstrate the application of swift and heavy ion implantation to generate optical waveguides in amorphous materials. Gallium lanthanum sulfide (GLS) and gallium lanthanum oxysulfide (GLSO) glass waveguides are fabricated using Ar implantation at 60 MeV and 2 × 10¹² ions/cm². A “well” region with increased refractive index (0.1% for GLS and 0.3% for GLSO) is formed near the surface of the glass based on the electronic energy deposition; a “barrier” layer with decreased refractive index is formed inside the glass due to the nuclear energy deposition. As a result, the waveguides exhibit a refractive index distribution of “well + barrier” type. It is supposed that the change in local structure order of the substrate causes the “well” formation. The propagation loss is 2.0 dB/cm for GLS and 2.2 dB/cm for the GLSO glass waveguide.     

Depth profiling of hydrogen under an atmospheric pressure

Nuclear reaction analysis of hydrogen with a use of the ¹H(¹⁵N,αγ)¹²C reaction was performed under a atmospheric condition. A 100 nm-thick silicon nitride membrane coated with gold of 10 nm was used for the extraction of the ¹⁵N beam into the sample chamber filled with gas molecules. Hydrogen contained in a Y film with a thickness of 80 nm was detected in N₂ of 10⁵ Pa. This nuclear reaction analysis (NRA) setup was also applied to H₂ gas, and the yield curve revealed a plateau feature. The plateau level was, furthermore, found to be constant independent of the H₂ pressure. We show that this plateau intensity can be used to obtain the detection efficiency of a NRA setup.