Evaluation of pulsed laser irradiation on concrete using a QCW laser system

Nguyen, P. L.; Daido, Hiroyuki; Matsunaga, Yukihiro; Hanari, Toshihide; Terada, Takaya; Yamada, Tomonori; Kawachi, Tetsuya

no journal, , 

Evaluation for THz light generation by contact grating device

Tsubouchi, Masaaki; Nagashima, Keisuke; Yoshida, Fumiko; Ochi, Yoshihiro; Maruyama, Momoko

no journal, , 

We have developed the Febry-Perot type contact grating device for intense THz generation. In this device, the grating to tilt the pulse front of the pump pulse is contacted on the LiNbO crystal. To realize the contact grating device, we employed the Febry-Perot cavity on the LiNbO crystal to obtain the high diffraction ratio of the grating. In this paper, we introduce the characteristic of the device, and discuss the intrinsic problems and its solutions.

High efficiency diffraction grating overcoated with oxide film for 5-20nm region

Koike, Masato; Nagano, Tetsuya*

no journal, , 

Boron (B) in the steel material can greatly contribute to the improvement of the quenching property by the addition in a few tens ppm level. Taking this advantage the automotive steel sheets becomes possible lighter remains maintained strength. However, in the steelmaking process, accurate control of the B addition quantity in ppm level is needed. Also there is a strong demand for detailed electronic structure analysis for boron compounds. The authors have found a unique method based on a new physical phenomenon, which can dramatically increase the diffraction efficiency of the laminar type diffraction grating coated with a metal single-layer film such as gold around B-K emission line (6.76 nm). This phenomenon, in the grazing incidence area where causes the total reflection, can be appeared by overcoating with a transparent and high density layer having a certain thickness on the metal coated grating grooves. For the overcoating layer, it is desirable to have an intermediate refractive index in vacuum and the metal layer. From this standpoint we did a search on the oxide films which are generally used as optical coating. Consequently, TiO, CeO, etc., were found to be promising candidates to meet this criterion. The results of numerical calculation shows that the diffraction efficiency of both TiO and CeO is 22% at 6.76 nm and it is a significant improvement from 15.6% and 14.1% for Ni and Au, respectively.

Irradiation effect in the fabrication of ErO film on the sputter-treated Si

Fujita, Masaya*; Asaoka, Hidehito; Yamaguchi, Kenji

no journal, , 

The ion beam sputter deposition method is capable of fabricating highly-oriented ErO thin film on crystalline Si substrate at 700 C, by bombarding ErO target with O ion beam. However, there always exists silicide phase (ErSi) due to direct reaction between sputtered Er atoms and the Si substrate. In order to find ways to prevent, or slow down the reaction of Si with Er, the dependence of the sputter-etching conditions of the substrate, which are conducted prior to deposition to remove surface impurities, on the film crystalline properties was investigated. In the experiment, two sputter-etching conditions, (a) fluence 3.710 ions cm (normally employed condition) and (b) 3.710 ions cm, were employed. The results of the film structure observed by XRD analysis indicated that the silicide phase was present irrespective of the fluence conditions employed.

Defect levels in GaAs pn diodes embedded with InAs quantum dot layers

Sato, Shinichiro; Schmieder, K.*; Hubbard, S.*; Forbes, D.*; Warner, J.*; Oshima, Takeshi; Walters, R.*

no journal, , 

III-V semiconductor devices embedded with quantum dots (QDs) are expected to be applied to next generation space solar cells. High density QDs and highly stacked QD layers without stacking fault are required in order to relaize QD solar cells, and have been obtained recently by using strain compensating technology. However, larger amount of defects are still incorporated into QD devices compared to single crystal devices and affect the device characteristics. In this study, we fabricated GaAs pn diode with 10 layers of InAs QDs by Metal Organic Vapor Phase Epitaxy (MOVPE) method and characterized defect levels in the devices using Deel Level Transient Spectroscopy (DLTS). The results were compared to reference samples which were GaAs pn diodes without InAs QDs. It was shown that unique electron and hole trap levels were found in the QD devices and thus we concluded that these traps should be reduced in order to improve the device quality.

XAFS study of single-layer graphene oxide grown on sapphire(0001)

Entani, Shiro; Honda, Mitsunori; Takizawa, Masaru*; Shimoyama, Iwao; Naramoto, Hiroshi*; Sakai, Seiji; Shamoto, Shinichi

no journal, , 

no abstracts in English

In situ synchrotron X-ray diffraction during MBE growth of nitride semiconductors

Takahashi, Masamitsu; Sasaki, Takuo; Deki, Ryota*

no journal, , 

no abstracts in English

In segregation and dislocation mechanisms of InGaAs under Stranski-Krastanow growth

Deki, Ryota*; Sasaki, Takuo; Takahashi, Masamitsu

no journal, , 

no abstracts in English

Design of a measurement system for laser-accelerated ion beams considering photo-neutrons effect

Kanasaki, Masato*; Jinno, Satoshi*; Sakaki, Hironao; Kondo, Kiminori; Oda, Keiji*; Yamauchi, Tomoya*; Fukuda, Yuji

no journal, , 

In laser-driven ion acceleration experiments using cluster-gas targets, a significant amount of fast electrons are produced that drive ion acceleration along with high energy ions with several-tens of MeV. In our recent experiment, the energy of the electrons reached as high as 200 MeV. Such fast electrons can produce photo-neutrons by bremsstrahlung processes followed by (, ) reactions. When the CR-39 nuclear track detector is exposed to such photo-neutrons, it records the etchable tracks of recoiled protons depending on their energy as unwanted background signals. To precisely diagnose laser-accelerated protons using CR-39, we have developed the discrimination method for laser- accelerated protons and photo-neutrons on CR-39 based on the incident angle and the incident energy.

How platinum nanoparticle catalysts are affected by ion-beam modification of their support

Kimata, Tetsuya*; Kato, Sho*; Yamaki, Tetsuya; Yamamoto, Shunya; Hakoda, Teruyuki; Kobayashi, Tomohiro*; Terai, Takayuki*

no journal, , 

Platinum (Pt) nanoparticles with high oxygen reduction reaction activity have been required for applications to polymer electrolyte fuel cells. We prepared the Pt nanoparticles on an Ar-ion-irradiated glassy carbon (GC) substrate by a radio-frequency sputtering method to investigate the influence of the ion-induced lattice defects in GC on the deposited Pt nanoparticles by X-ray photoelectron spectroscopy (XPS). Detailed examination of both the Pt 4f and C 1s XPS spectra demonstrated that Pt-C bonding interaction occurred at the interface between the irradiated GC and Pt nanoparticles, confirming the significant effect of the Ar-ion irradiation on the electronic properties of Pt.

Surface temperature dependence of oxidation of Cu3Au(111)

Tsuda, Yasutaka*; Makino, Takamasa*; Okada, Michio*; Yoshigoe, Akitaka; Teraoka, Yuden

no journal, , 

Oxidation processes of alloy materials are important chemical reactions for the fabrication of protective layers used in various industrial applications. In this study, surface temperature dependence of oxidation of CuAu(111) was studied using synchrotron radiation XPS and molecular beams. It was found that no dependence among uptake curves was observed from 300 to 500 K in low oxygen dosage because a direct dissociative adsorption takes place in this incident energy region. In contrast, clear difference between 400 and 500 K due to CuO formation was observed. This result suggests that thermal-driven diffusion of Au atoms into bulk depress the protective function for oxidation.