Kensuke Murai

Electrochromic properties of spin-coated nickel oxide films

Abstract Nickel 2-ethylhexanoate was spin-coated from organic solution, followed by pyrolysis in air at 380°C. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis showed that the spin-coated films consisted of fine particles of NiO crystallites, 10–20 nm in diameter. The optical response and cycling ability of the films were measured by applying a rectangular potential pulse between 0.0 and 0.5 V vs. SCE in a 1 M KOH electrolyte. The influence of the processing temperature on the electrochromic properties of the films was studied. Although the films pyrolyzed in air at 380°C showed the response time of 1–2 s for coloration/bleaching, the degradation was observed within a few thousands to 10 4 cycles. The cycling ability could be much improved by post heat-treatment at 500°C for 20 min in air without sacrificing the response speed.

Pulsed Laser Deposition of Crystalline Indium Tin Oxide Films at Room Temperature by Substrate Laser Irradiation

Crystalline tin (Sn)-doped indium oxide (ITO) films grown at room temperature (RT) using pulsed laser deposition (PLD) coupled with laser irradiation of the growing films are discussed. The energy of the laser irradiation beam was ~0.07 Jcm-2. The films were deposited from Sn-doped (0–10 wt%) In2O3 targets under oxygen pressure (PO2 ) of 10-2 Torr. At RT, the laser-irradiated and nonirradiated portions of the films yielded resistivities of ~1.2×10-4 and ~2.5×10-4 Ωcm, respectively. At 200°C, a resistivity of 8.9×10-5 Ωcm was observed for the laser-irradiated part of the ITO films.

Surface Modification of Poly(methyl methacrylate) by Hydrogen-Plasma Exposure and Its Sputtering Characteristics by Ultraviolet Light Irradiation

Surface modification of poly(methyl methacrylate) (PMMA) films by hydrogen-plasma exposure has been studied in the light of sputtering resistance of polymer-based materials in plasma etching processes. Surface measurements of PMMA were performed with X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and spectroscopic ellipsometry. It has been found that oxygen atoms are preferentially removed from the surface when a PMMA film is subjected to hydrogen-plasma exposure, with the depth of modification being about 40 nm in the case we examined. Hydrogen-plasma exposure is also found to reduce the sputtering yields of PMMA by ultraviolet light irradiation, as in the case of Ar+ ion irradiation [S. Yoshimura et al.: J. Vac. Soc. Jpn. 56 (2013) 129]. The results suggest that PMMA films become hardened and more sputtering resistant due to the formation of a thick (i.e., 40 nm in the case of this study) amorphous carbon layer by hydrogen-plasma exposure. Hydrogen-plasma exposure is thus an effective technique to increase etching resistance of polymer films.

Electrochromic properties of nickel oxide films prepared by the oxidation of nickel-carbon composite films

Electrochromic (EC) nickel oxide (NiO) films were prepared either by plasma oxidation of vacuum-deposited nickel-carbon (Ni–C) composite films or by thermal oxidation of those films. EC properties of the NiO films were measured by cyclic voltammetry in 1 M KOH. The degree of electrochromism in the NiO films depended not only on the Ni-to-C (Ni/C) ratio in the Ni–C films but also on the oxidation conditions of the Ni–C films. The NiO film with a Ni/C ratio of ~0.6 showed the longest cycling ability among the films with three different Ni/C ratios (~0.3, ~0.6 and ~1.2). The NiO film thermally oxidized at 500° C showed smaller transmission modulation and passed charge density than the plasma oxidized film, but could be electrochemically switched for more than 5000 cycles without serious residual coloration.

Focusing efficiency of a multilayer Fresnel zone plate for hard X-ray fabricated by DC sputtering deposition

Abstract A hard X-ray microbeam with submicrometer spot size from third-generation high brilliance synchrotron radiation (SR) sources is expected to be a powerful tool for various fields of research. A Fresnel zone plate (FZP) is one of the promising, focusing elements for X-rays. Focusing efficiency is one of the important features of the FZP. In order to fabricate an FZP with a high focusing efficiency, it is necessary to investigate the relation between the experimental values of the focusing efficiency and the theoretical ones. We have fabricated Ag/C and Cu/Al multilayer (sputtered-sliced) FZPs for use in hard X-ray region, and have compared the measured focusing efficiency data with the calculated ones. The experimental data have been in good agreement with the theoretical values.

Double-Pass Amplification in Ge Soft X-Ray Laser with a Polarizing Half-Cavity

The control of polarization of soft X-ray lasers is presented. Double-pass amplification in a soft X-ray laser with a half-cavity comprising a multilayer polarizer and a normal incidence reflector has been tested. Successful results have been obtained using a curved-slab target for the lasing line at 19.6 nm due to the J=0–1 transition of the collisional-excitation neonlike germanium soft X-ray laser.

Spatial Coherence Measurement of 13.9 nm Ni-like Ag Soft X-Ray Laser Pumped by a 1.5 ps, 20 J Laser

In this paper, we report the first measurement of the time-integrated spatial coherence of the Ni-like Ag X-ray laser at 13.9 nm pumped by a 1.5 ps, 20 J Nd glass laser, in which the transient collisional excitation (TCE) pumping scheme is realized. The time-integrated complex coherence factor (CCF) of the X-ray laser has been determined from partially coherent diffraction patterns of a multislit array placed 1 m away from the X-ray laser source. The transverse coherence lengths in the directions horizontal and vertical to the Ag target surface are estimated respectively to be within 110 µm to 140 µm at a position 1 m from the X-ray laser source. We tried to explain the profile of the CCF with a quasi-monochromatic incoherent source model with various profiles.

Intense Nickel-like Neodymium X-Ray Laser at 7.9 nm with a Double-Curved-Slab Target

We have demonstrated triple-pulse lasing combined with an X-ray mirror with 4 pumping pulses in Ni-like Nd at 7.9 nm. Intense triple-pulse X-ray laser radiation has been generated with a double-curved-slab target, which was irradiated with laser pulses of quasi-traveling wave configuration, using cylindrical lens arrays for uniform pumping. An order of magnitude higher X-ray laser pulse energy was observed along the forward-traveling wave direction compared to the backward-traveling wave direction. Output energy in the forward direction was estimated to be ~40 µJ.

Electrochromism in nickel oxide films prepared by plasma oxidation of nickel-carbon composite films

Abstract We report on a novel dry process for preparing NiO films by plasma oxidation of NiC composite films, which have been deposited by co-evaporation of Ni and C from two different sources. After being hydrated in KOH electrolyte, the NiO films show fast response and good cycling ability.

Low-energy SiC2H6+ and SiC3H9+ ion beam productions by the mass-selection of fragments produced from hexamethyldisilane for SiC film formations

We have been attempting to produce low-energy ion beams from fragments produced through the decomposition of hexamethyldisilane (HMD) for silicon carbide (SiC) film formations. We mass-selected SiC2H6+ and SiC3H9+ ions from fragments produced from HMD, and finally produced low-energy SiC2H6+ and SiC3H9+ ion beams. The ion energy was approximately 100 eV. Then, the ion beams were irradiated to Si(100) substrates. The temperature of the Si substrate was 800°C during the ion irradiation. The X-ray diffraction and Raman spectroscopy of the substrates obtained following SiC2H6+ ion irradiation demonstrated the occurrence of 3C-SiC deposition. On the other hand, the film deposited by the irradiation of SiC3H9+ ions included diamond-like carbon in addition to 3C-SiC.