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Journal Articles

Surface stress measurement of Si(111) 7$$times$$7 reconstruction by comparison with hydrogen-terminated 1$$times$$1 surface

Asaoka, Hidehito; Uozumi, Yuki

Thin Solid Films, 591(Part B), p.200 - 203, 2015/09

We have focused on measurements of the surface stress in Si(111) as a function of 7$$times$$7 reconstruction by comparison with the hydrogen (H)-terminated Si(111) 1$$times$$1 surface. In order to obtain information on both the surface stress and the surface reconstruction simultaneously, we have combined the surface-curvature and the reflection-high-energy-electron-diffraction instrumentations in an identical ultrahigh vacuum system. The stress evolution shows a decrease of tensile stress corresponding to the formation of H-termination at the beginning of the atomic H exposure of Si(111) 7$$times$$7 surface. After the above treatment, a complete transformation of the surface structure occurs from the reconstructed surface to the 1$$times$$1 one. As a result, we find the H-terminated Si(111) 1$$times$$1 surface releases 1.7 N/m (=J/m$$^{2}$$), or (1.4 eV/(1$$times$$1 unit cell)), of the surface energy from the strong tensile Si(111) 7$$times$$7 reconstruction.

Journal Articles

Development of a compact polarization analysis apparatus for plasma soft X-ray laser

Imazono, Takashi; Koike, Masato

Thin Solid Films, 571(Part 3), p.513 - 516, 2014/11

 Times Cited Count:2 Percentile:10.87(Materials Science, Multidisciplinary)

A laser-driven plasma soft X-ray laser (SXRL) system was constructed in Kansai Photon Science Institute. The SXRL having a 7-ps-duration pulse at a wavelength of 13.9 nm is generated from nickel-like silver plasmas generated by 10 J and ps-duration Nd:glass laser pulse. The polarization state of SXRL is considered to be almost vertically linearly polarized at the end station by the reflections of some Mo/Si multilayer mirrors installed in the SXRL beamline, but it has not been measured experimentally due to the lack of a polarization analysis apparatus. Therefore, we have developed a compact soft X-ray ellipsometer to be able to be installed in the SXRL beamline and evaluated the degree of linear polarization of SXRL with a Mo/Si multilayer polarizer whose polarization property has been characterized by using synchrotron radiation in advance.

Journal Articles

Plasmonic cyclohexane-sensing by sputter-deposited Au nanoparticle array on SiO$$_{2}$$

Kawaguchi, Kazuhiro*; Yamamoto, Shunya; Yoshikawa, Masahito; Takahiro, Katsumi*

Thin Solid Films, 562, p.648 - 652, 2014/07

 Times Cited Count:4 Percentile:21.37(Materials Science, Multidisciplinary)

Liquid organic-hydrides such as cyclohexane which can release-absorbing hydrogen in reversible have been proposed approvable carriers to store and transport hydrogen. However, organic-hydrides are known as highly flammable in air. To realize practical use of this hydrogen production process, the monitoring of leakage of organic-hydride gas is strongly required. In the present work, we have examined the plasmonic sensing ability of Au nanoparticle (NP) arrays for dilute cyclohexane. Au NP arrays were prepared on SiO$$_{2}$$ by a sputter deposition technique. The change in an extinction spectrum of Au NP arrays before and after exposure of cyclohexane vapor enabled us to detect it. The Au NP array prepared with 4.4 $$times$$ 10$$^{16}$$ Au atoms/cm$$^{2}$$ deposited at 300$$^{circ}$$C was and demonstrated a high sensitivity for cyclohexane at RT. The experimentally detectable concentration of cyclohexane was as low as 0.5 vol%, much lower than its explosion limit (1.3 vol%).

Journal Articles

Electrochemical immobilization of biomolecules on gold surface modified with monolayered L-cysteine

Honda, Mitsunori; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie

Thin Solid Films, 556, p.307 - 310, 2014/04

 Times Cited Count:5 Percentile:26.26(Materials Science, Multidisciplinary)

Journal Articles

Preparation of a dense TiO$$_{2}$$ thin film by oxidizing metallic titanium

Yoshida, Fumiko; Tanaka, Momoko; Nagashima, Keisuke

Thin Solid Films, 537, p.23 - 27, 2013/06

 Times Cited Count:2 Percentile:11.28(Materials Science, Multidisciplinary)

Journal Articles

Analysis of buried heterointerfacial hydrogen in highly lattice-mismatched epitaxy on silicon

Yamazaki, Tatsuya; Asaoka, Hidehito; Taguchi, Tomitsugu; Yamamoto, Shunya; Yamazaki, Dai; Maruyama, Ryuji; Takeda, Masayasu; Shamoto, Shinichi

Thin Solid Films, 520(8), p.3300 - 3303, 2012/02

 Times Cited Count:2 Percentile:10.73(Materials Science, Multidisciplinary)

We succeeded in realizing the epitaxial growth of a Sr layer on Si(111) with an atomically abrupt heterointerface - in spite of its large lattice mismatch (12%) with Si - by introducing a monoatomic layer of H on Si. In order to identify the buried H, we carried out a combination analysis involving neutron reflectometry and resonant nuclear reaction of $$^{1}$$H($$^{15}$$N,$$alpha$$$$gamma$$)$$^{12}$$C analysis. We found different neutron reflectivity profiles resulting from a contrast variation between the H and D atoms at the buried heterointerface. Furthermore, the depth $$gamma$$-ray intensity profiles revealed that the H at the heterointerface acts as an effective buffer layer that enables it to manage the highly mismatched epitaxy on Si.

Journal Articles

Formation of atomically flat $$beta$$-FeSi$$_{2}$$/Si(100) interface using ion irradiated substrate

Sasase, Masato*; Yamamoto, Hiroyuki; Kurata, Hiroki*

Thin Solid Films, 520(9), p.3490 - 3492, 2012/02

 Times Cited Count:0 Percentile:0.02(Materials Science, Multidisciplinary)

Thin uniform $$beta$$-FeSi$$_{2}$$ films were fabricated on ion irradiated Si(100) substrates to achieve an atomically flat interface. Ion irradiation produces a surface with more defects than chemical etching, however, it is expected that the presence of defects can promote the formation of compound films such as $$beta$$-FeSi$$_{2}$$ that require interdiffusion and reaction processes. However, excess defects can also result in random nucleation, poor crystallinity and a rough interface. Cross-sectional transmission electron microscopy was used to determine the optimum conditions for ion irradiation of the substrate to obtain a clear $$beta$$-FeSi$$_{2}$$/Si interface.

Journal Articles

Ion channeling study of epitaxy of iron based Heusler alloy films on Ge(111)

Maeda, Yoshihito; Narumi, Kazumasa; Sakai, Seiji; Terai, Yoshikazu*; Hamaya, Kohei*; Sado, Taizo*; Miyao, Masanobu*

Thin Solid Films, 519(24), p.8461 - 8467, 2011/10

 Times Cited Count:7 Percentile:34.63(Materials Science, Multidisciplinary)

Journal Articles

Orientation of B-C-N hybrid films deposited on Ni (111) and polycrystalline Ti substrates explored by X-ray absorption spectroscopy

Mannan, M. A.; Baba, Yuji; Kida, Tetsuya*; Nagano, Masamitsu*; Shimoyama, Iwao; Hirao, Norie; Noguchi, Hideyuki*

Thin Solid Films, 519(6), p.1780 - 1786, 2011/01

 Times Cited Count:18 Percentile:62.01(Materials Science, Multidisciplinary)

Orientation of BCN hybrid films synthesized on Ni (111) and Ti substrates by radio frequency plasma enhanced chemical vapor deposition has been investigated. Formation of the $$sp$$$$^{2}$$-BCN hybrids was confirmed by X-ray diffraction. Raman spectra also suggested the presence of graphite-like $$sp$$$$^{2}$$-BCN hybrid bonds. Orientation and local structures of the films were studied by the near-edge X-ray absorption fine structure (NEXAFS) measurements using synchrotron radiation. The B K-edge NEXAFS spectra revealed the preferred formation of the $$sp$$$$^{2}$$-BCN hybrid configuration around the B atoms like-BN$$_{3}$$ on Ni (111). It was revealed that the BCN film is parallel to the surface on Ni(111). On the other hand, the film is randomly oriented on Ti surface. It was suggested that the chemical reactivity of the metal surface affects the orientation of the BCN hybrid film.

Journal Articles

Growth and characterization of stoichiometric BCN films on highly oriented pyrolytic graphite by radiofrequency plasma enhanced chemical vapor deposition

Mannan, M. A.; Noguchi, Hideyuki*; Kida, Tetsuya*; Nagano, Masamitsu*; Hirao, Norie; Baba, Yuji

Thin Solid Films, 518(15), p.4163 - 4169, 2010/05

 Times Cited Count:24 Percentile:70.15(Materials Science, Multidisciplinary)

Hexagonal boron carbonitride (h-BCN) hybrid films have been synthesized on highly oriented pyrolytic graphite by radiofrequency plasma enhanced chemical vapor deposition using tris-(dimethylamino)borane as a single-source molecular precursor. The films were characterized by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS) and Raman spectroscopic measurements. XPS measurement showed that the B atoms were bonded to C and N atoms to form the $$sp$$$$^{2}$$ BCN hybrid chemical environment. The atomic composition estimated from the XPS of the typical sample was found to be almost B1C1N1. NEXAFS spectra of the B K-edge and the N K-edge had the peaks due to the $$pi$$$$^{*}$$ and $$sigma$$$$^{*}$$ resonances of $$sp$$$$^{2}$$ hybrid orbitals implying the existence of the $$sp2$$ hybrid configurations of h-BCN around the B atoms.

Journal Articles

Radiation-induced luminescence from TiO$$_{2}$$ by 10 keV O$$^{+}$$, N$$^{+}$$ and Ar$$^{+}$$ ion irradiation

Kitazawa, Sin-iti; Saito, Yuichi; Yamamoto, Shunya; Asano, Masaharu; Ishiyama, Shintaro

Thin Solid Films, 517(13), p.3735 - 3737, 2009/03

 Times Cited Count:1 Percentile:6.48(Materials Science, Multidisciplinary)

Radiation-induced luminescence (RIL) produced by 10 keV O$$^{+}$$, N$$^{+}$$ and Ar$$^{+}$$ irradiation at room temperature has been used to study energy transfer in titanium dioxide (TiO$$_{2}$$) targets. RIL spectra in the UV-visible region show numerous atomic lines and three bands. Two visible bands by crystalline defects and an UV band at 3.9 eV originating from radiation transitions between the Ti$$^{3+}$$ 3d and O$$^{2-}$$ 2s states in the TiO$$_{2}$$ crystal are observed. The experimental results suggest that the excitations were not mainly produced by transitions from the ground state to excited states but by cascade radiations from higher excited states.

Journal Articles

Photoluminescence characterization of $$beta$$-FeSi$$_{2}$$ prepared by ion beam sputter deposition (IBSD) method

Zhuravlev, A. V.; Yamamoto, Hiroyuki; Shimura, Kenichiro*; Yamaguchi, Kenji; Shamoto, Shinichi; Hojo, Kiichi; Terai, Takayuki*

Thin Solid Films, 515(22), p.8149 - 8153, 2007/08

 Times Cited Count:3 Percentile:18.6(Materials Science, Multidisciplinary)

A semiconducting silicide, $$beta$$-FeSi$$_{2}$$, formed on a Si substrate, is known to exhibit strong photoluminescence (PL) peak at around 0.8 eV when it is annealed at high temperature (1073-1173 K). On the other hand, dislocation-related band of Si has intensity maxima at 0.81 eV. In the present study, the PL spectra were taken at the various stages of IBSD in order to understand the processes that are responsible for the observed PL enhancement. We observed a strong PL peak at around 0.8 eV in IBSD-grown $$beta$$-FeSi$$_{2}$$ film on Si substrate, as well as in substrate itself, upon thermal annealing in air at 1153 K. The most pronounced peak at 0.8 eV was observed when Si substrates were sputter etched by Ne$$^{+}$$, prior to the thermal annealing in air. However, the temperature dependence of peak intensity of $$beta$$-FeSi$$_{2}$$ was different from that of SE-treated Si, where thermal quenching appeared to occur at slightly lower temperature in the former.

Journal Articles

Growth of $$beta$$-FeSi$$_2$$ thin films on $$beta$$-FeSi$$_2$$ (110) substrates by molecular beam epitaxy

Muroga, Masataka*; Suzuki, Hirokazu*; Udono, Haruhiko*; Kikuma, Isao*; Zhuravlev, A. V.; Yamaguchi, Kenji; Yamamoto, Hiroyuki; Terai, Takayuki*

Thin Solid Films, 515(22), p.8197 - 8200, 2007/08

 Times Cited Count:6 Percentile:32.45(Materials Science, Multidisciplinary)

Semiconducting ${it $beta$}$-FeSi$$_2$$ has received much attention as a material for Si-based optoelectronic devices. There are a number of studies on heteroepitaxy of ${it $beta$}$-FeSi$$_2$$ film on Si. However, growth experiments of ${it $beta$}$-FeSi$$_2$$ film on single crystalline ${it $beta$}$-FeSi$$_2$$ substrate have not been investigated yet. Recently, single crystalline ${it $beta$}$-FeSi$$_2$$ with large growth facets by solution growth method using Ga solvent. By obtaining a smooth surface on the substrate, we have succeeded in growing ${it $beta$}$-FeSi$$_2$$ film on ${it $beta$}$-FeSi$$_2$$(110) substrate using molecular-beam epitaxy.

Journal Articles

Single crystalline $$beta$$-FeSi$$_{2}$$ grown using high-purity FeSi$$_{2}$$ source

Goto, Kohei*; Suzuki, Hirokazu*; Udono, Haruhiko*; Kikuma, Isao*; Esaka, Fumitaka; Uchikoshi, Masahito*; Isshiki, Minoru*

Thin Solid Films, 515(22), p.8263 - 8267, 2007/08

 Times Cited Count:14 Percentile:55.22(Materials Science, Multidisciplinary)

We have investigated the effect of FeSi$$_{2}$$ source purity on the electrical property of $$beta$$-FeSi$$_{2}$$ grown from solution. A high purity FeSi$$_{2}$$ source avoided a contamination of Cu and W metals was synthesized by melting a high purity Fe (5N) and Si (5N-up) in a quartz ampoule. The $$beta$$-FeSi$$_{2}$$ crystals grown using the high purity FeSi$$_{2}$$ and Zn solvent showed n-type conduction, whereas those grown using the arc-melted FeSi$$_{2}$$ showed p-type. From the SIMS analysis of the grown crystals, we found that dominant impurity concentrations in the p-type crystals were higher than those in the n-type ones.

Journal Articles

Comparative study of structures and electrical properties in cobalt-fullerene mixtures by systematic change of cobalt content

Sakai, Seiji; Naramoto, Hiroshi*; Avramov, P.; Yaita, Tsuyoshi; Lavrentiev, V.; Narumi, Kazumasa; Baba, Yuji; Maeda, Yoshihito

Thin Solid Films, 515(20-21), p.7758 - 7764, 2007/07

 Times Cited Count:22 Percentile:67.42(Materials Science, Multidisciplinary)

A systematic study is performed for the Co content-dependent structure evolution and electrical properties in the cobalt(Co)-fullerene(C$$_{60}$$) mixtures in the broad content region. Raman analysis confirms that the mixture has a saturation composition of Co$$_{5}$$C$$_{60}$$ for the compoundformation. An important role of the covalent Co-C bonds for the characteristic structure and the properties in the Co-C$$_{60}$$ compounds is concluded from the content-dependent peak shifts and the symmetry lowering of C$$_{60}$$. The Co-dilute mixtures exhibit a semiconductive nature represented bythe activated transport from the shallow mid-gap states. The Co-dense mixtures are characterized by hopping conduction (including variable rangehopping) attributed to the Co clusters/nanoparticles in the compound matrix and by the percolated metallic conduction, depending on the Co content.

Journal Articles

Development of neutron supermirrors with large critical angle

Maruyama, Ryuji; Yamazaki, Dai; Ebisawa, Toru*; Hino, Masahiro*; Soyama, Kazuhiko

Thin Solid Films, 515(14), p.5704 - 5706, 2007/05

 Times Cited Count:38 Percentile:80.45(Materials Science, Multidisciplinary)

The development of neutron supermirrors is important for neutron scattering experiments since it offers a considerable increase in the available neutron intensity. Up to now, many studies have been carried out to realize high reflectivity and large $$m$$, where $$m$$ is the ratio of the effective critical angle of the supermirror to that of natural nickel. We have developed neutron supermirrors by employing the ion beam sputtering (IBS) technique because it enables the production of layers with high density and small grain size. Although the IBS technique produces high quality layers, its disadvantage is that the deposition area is relatively small. In order to produce the optical devices using supermirrors, which is planned in the project of a new spallation neutron source (Japan Proton Accelerator Research Complex, J-PARC), a new IBS instrument with a large deposition area whose diameter is 500 mm has been designed and installed at the Japan Atomic Energy Agency. The deposition rate has been confirmed to be almost uniform over the entire deposition area. We have carried out the development of Ni/Ti supermirror with large $$m$$. In this presentation, the performance of those supermirrors fabricated with the IBS instrument is discussed.

Journal Articles

Rutile and anatase mixed crystal TiO$$_2$$ thin films prepared by pulsed laser deposition

Kitazawa, Sin-iti; Choi, Y.*; Yamamoto, Shunya; Yamaki, Tetsuya

Thin Solid Films, 515(4), p.1901 - 1904, 2006/12

 Times Cited Count:71 Percentile:91.65(Materials Science, Multidisciplinary)

The epitaxial growths of titanium dioxide (TiO$$_2$$) thin films were prepared by pulsed laser deposition. The dependences of the crystalline structure of prepared films upon buffer O$$_2$$ gas pressure, laser power and substrate were studied. The crystalline structures were found by the X-ray diffraction method to be a mixture of rutile and anatase on $$alpha$$-Al$$_2$$O$$_3$$, and anatase on LaAlO$$_3$$. The crystallite sizes were calculated to be about 10 nm by applying the Scherrer equation to the diffraction peaks. The sizes were increased by collisions between evaporated particles and O$$_2$$. The growth of mixed crystal is caused by the competitive process between lattice misfit-induced epitaxy and thermodynamic stability.

Journal Articles

Effect of thermal annealing on the photoluminescence from $$beta$$-FeSi$$_2$$ films on Si substrate

Yamaguchi, Kenji; Shimura, Kenichiro; Udono, Haruhiko*; Sasase, Masato*; Yamamoto, Hiroyuki; Shamoto, Shinichi; Hojo, Kiichi

Thin Solid Films, 508(1-2), p.367 - 370, 2006/06

 Times Cited Count:12 Percentile:50.74(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

In situ characterization of the heterointerfaces between SrO films and dangling-bond-terminated Si surfaces

Asaoka, Hidehito; Yamazaki, Tatsuya*; Yamamoto, Hiroyuki; Shamoto, Shinichi

Thin Solid Films, 508(1-2), p.175 - 177, 2006/06

 Times Cited Count:4 Percentile:23.48(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Consumption kinetics of Si atoms during growth and decomposition of very thin oxide on Si(001) surfaces

Ogawa, Shuichi*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Teraoka, Yuden; Takakuwa, Yuji*

Thin Solid Films, 508(1-2), p.169 - 174, 2006/06

 Times Cited Count:12 Percentile:50.74(Materials Science, Multidisciplinary)

The surface morphological change during growth and subsequent decomposition of very thin oxide on Si(001) surface was observed in real time by RHEED combined with AES and macroscopically by STM. The RHEED intensity ratio between half-order spots revealed that etching of the surface took place in a manner of nucleation and lateral growth of dimer vacancy on the terrace during two-dimensional (2D) oxide island growth at 690$$^{circ}$$C, whereas the resultant oxide layer was decomposed at 709$$^{circ}$$C with consumption of Si atom in a step flow mode. STM observation of the partially oxide decomposed surface, however, showed that a number of Si islands with 10-20 angstrom in diameter remained randomly over the rather atomically flat terraces within voids in spite of the step-flow etching. These results are considered in terms of the phase separation of Si-rich oxide grown by 2D oxide island growth mode between Si clusters and a stoichiometric SiO$$_{2}$$ matrix and subsequent precipitation of Si islands on the terrace during decomposition.

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