Shigeharu Tamura

Microbeam of 100 keV x ray with a sputtered-sliced Fresnel zone plate

Microfocusing of 100 keV x ray with a sputtered-sliced Fresnel zone plate (ss-FZP) has been performed at the 250-m-long beamline (20XU) of SPring-8. The ss-FZP with an outermost zone width 0.16 μm which is composed of 70 layers of alternating Cu and Al layers and having thickness ∼180 μm was fabricated and characterized. The minimum focal spot size attained for the first order focal beam was 0.5 μm with a focal distance 900 mm at a photon energy 100 keV. The total flux of the microprobe was ∼2×106 photons s−1 μm−2.

Development of a multilayer Fresnel zone plate for high-energy synchrotron radiation X-rays by DC sputtering deposition

Hard X-ray microscopy with high spatial resolution (<or=0.1 microm) using a high-energy and high-brilliance X-ray microprobe is expected to be a promising technology for various types of analysis, imaging etc. in materials science, biology and medicine. A multilayer Fresnel zone plate (FZP) could be a promising approach to focusing optics in the high-energy X-ray region (>or=20 keV) because a large thickness (aspect ratio) can be available. Various types of multilayer FZPs have been fabricated by DC sputtering deposition. Their focusing characteristics have been evaluated at the high-brilliance undulator beamline BL47XU of SPring-8. An optical system using a Cu/Al multilayer FZP (with an outermost zone width of 0.25 microm) as the focusing optics fabricated by the optimum deposition condition with precise film (zone) thickness control has attained an almost diffraction-limited microbeam of 0.3-0.35 microm at 8.9 keV. A line-and-space resolution test pattern has been observed: fine structures up to 0.2 microm were clearly observed in the measured image. This FZP has been working since 1995, keeping good focusing characteristics. It can be said from these results that a spatial resolution better than 0.1 microm in the high-energy X-ray region is in prospect by the development of a multilayer FZP with a narrower outermost zone width in the near future.

Highly conductive transparent F-doped tin oxide films were prepared by photo-CVD and thermal-CVD

Abstract Although high-quality SnO 2 films have been prepared above 400°C, we prepared highly-conductive transparent F-doped SnO 2 films below about 350°C and at high growth rates, using a new raw material system of Sn(CH 3 ) 4 , O 2 containing 5 mol.% O 3 , and HF-acid. At a substrate temperature of 350°C, the films, which had properties such as sheet resistances of 1.6 and 4.5 Ω /□, resistivities of 3.4 and 4.5 × 10 −4 Ω cm, and transmittances including substrates of 70% and 80% at 550 nm, were prepared by thermal-CVD and photo-CVD (chemical vapour deposition), respectively. Several optical and electrical properties of the films prepared by both CVD methods were compared.

Fabrication of a hard x-ray sputtered-sliced Fresnel phase zone plate

A Fresnel phase zone plate for hard x ray was fabricated by physical vapor deposition alternating transparent and opaque layers onto a fine gold wire core 47 μm in diameter. The zone plate, which is comprised of 25 pairs of alternating Ag and C layers, is designed to operate with a focal length of 124 mm for a parallel beam at 8.1 keV. The thickness of the zone plate is less than 10 μm and is capable of operating as a phase zone plate. Using the brilliant monochromatized x-ray beam from the TRISTAN Main Ring, with an undulator, the minimum focal spot size attained for the first order focal beam was 0.5 μmφ. The light collecting efficiency was determined to be near 11%.

Optical humidity sensitivity of plasma-oxidized nickel oxide films

Abstract We report on the optical humidity sensitivity of nickel oxide (NiO) films prepared by plasma oxidation of nickel–carbon composite films. The plasma-oxidized NiO films showed humidity-sensitive absorbance change at room temperature. The optical absorbance change was strongest at wavelengths around 560 nm. The reversible absorbance change over a wide humidity range of 0–90% RH and the response time within several minutes were obtained with the plasma-oxidized NiO films which is a potential candidate for optical humidity detection.

Transparent conductive tin oxide films by photochemical vapour deposition

Abstract Photochemical vapour deposition (photo-CVD) is expected to be a damage-free process at low temperature. Transparent conductive tin oxide (non-doped) films have been prepared by the photo-CVD process under various deposition conditions. TMT (Sn (CH3)4) and O2 (containing 4 mol.% O3) were used as the raw materials and a low-pressure mercury lamp was used as the light source. By the combination of linearly focused low-pressure mercury lamp light through a semi-cylindrical suprasil window and a reciprocation motion of the substrate, a good uniformity of the film thickness along an 8 × 10 cm area was realised. The growth rate was proportional to both the substrate temperature and the TMT flow rate. The minimum resistivity of ~ 7 × 10−3 Ω cm was obtained at a substrate temperature of 250 °C.

Hard X-ray microbeam experiments with a sputtered-sliced Fresnel zone plate and its applications.

Hard X-ray microbeam experiments with sputtered-sliced Fresnel zone plates have been performed. Zone plates with an outermost zone width of 0.25 microm (#FZP1) and 0.1 microm (#FZP2) were fabricated and evaluated. In a scanning X-ray microscopy experiment, a line-and-space pattern with structure as fine as 0.1 microm was resolved using #FZP2 at an X-ray wavelength of 1 A. As an application of the microbeam technique, a two-dimensional distribution of constituent elements in forensic samples has been obtained (e.g. section view of human and elephant hairs) using fluorescent scanning microscopy.

Hard X-ray Microbeam Experiment at the Tristan Main Ring Test Beamline of the KEK

A hard X-ray microbeam with zone-plate optics has been tested at the MR-BW-TL beamline on the Tristan main ring of the KEK, and preliminary experiments on scanning microscopy have also been performed. A sputtered-sliced Fresnel zone plate with an Au core and Ag/C multilayer is used as an X-ray focusing device. The outermost zone width of the zone plate is 0.25 microm. A focused spot size of approximately 0.5 mum has been achieved at an X-ray energy of 8.54 keV. In a scanning X-ray microscopy experiment, test patterns with submicrometer fine structure have been clearly resolved.

Zernike-type X-ray imaging microscopy at 25 keV with Fresnel zone plate optics

A Zernike-type imaging microscope using a sputtered-sliced Fresnel zone plate (SS-FZP) has been developed and tested at an X-ray energy of 25 keV. The SS-FZP was used as an objective. A copper (Cu) phase plate was placed at the back focal plane of the SS-FZP in order to produce phase contrast. The performance of the Zernike-type imaging microscope was tested with a gold (Au) mesh and a resolution test pattern at undulator beamline 47 of SPring-8. The Au mesh and the resolution test pattern could be imaged in transmission with a magnification of x10.2. Owing to the Cu phase plate, different image contrast was observed compared with the bright-field image contrast. Tantalum microstructures down to 0.5 microm line-and-space have been observed on spatial resolution test patterns.

Fabrication and testing of hard x‐ray sputtered‐sliced zone plate

A sputtered‐sliced hard x‐ray zone plate has been made by the physical vapor deposition of alternating transparent and opaque layers onto a fine gold wire core of 50 μm diameter. The zone plate is designed to operate with a focal length of 124 mm at 8.05 eV and consists of 25 pairs of alternating Ag and C layers with a thickness of ∼40 μm along the wire axis. Using monochromized synchrotron x ray with an energy of 8.05 keV the minimum focal spot size attained for the first order focal beam was 2.3 μm in the vertical and horizontal directions, respectively. The light‐collecting efficiency was determined to be ∼4%. The focal spot size obtained was substantially larger than the 1.2 μm φ spatial resolution predicted from the contradiction of the light source size.