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Volume 49, Issue 12
Displaying 1-20 of 20 articles from this issue
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Foreword
Reviews
  • Current-driven Domain Wall Motion and its Application to Spintronic Devices
    Teruo ONO
    2006 Volume 49 Issue 12 Pages 692-694
    Published: 2006
    Released on J-STAGE: August 09, 2007
    DOIhttps://doi.org/10.3131/jvsj.49.692
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  • Magnetic Interface Effects in Metallic Multilayers
    Ko MIBU
    2006 Volume 49 Issue 12 Pages 695-699
    Published: 2006
    Released on J-STAGE: August 09, 2007
    DOIhttps://doi.org/10.3131/jvsj.49.695
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      The interfaces in multilayers are expected to be fertile in novel magnetic properties, due to a break in translation symmetry of the constituent atoms. In this article, some methods to examine interface magnetism are briefly reviewed. Examples of magnetic interface effects are shown for multilayers containing antiferromagnetic Cr layers.
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  • Highly Spin-polarized Full-Heusler Alloy Films and Their Application to Spin-electronics Devices
    Kay YAKUSHIJI, Koki TAKANASHI
    2006 Volume 49 Issue 12 Pages 700-705
    Published: 2006
    Released on J-STAGE: August 09, 2007
    DOIhttps://doi.org/10.3131/jvsj.49.700
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      The recent development of the study on half-metallic full-Heusler alloy thin films and their application to spin-electronics devices are reviewed. The progress of preparation technique of Co-based full-Heusler alloy films with high L21 structural order has made it possible to obtain higher spin-polarization than that of typical transition metals and alloys (Co, CoFe, etc.). Resulting tunnel magnetoresistance in magnetic tunnel junctions exceeds 60% at room temperature. Our recent results on the current-perpendicular-to-plane magnetoresistance (CPP-GMR) devices with Co2MnSi films are also shown. The resistance change-area product (ΔRA) at room temperature was 19 mΩμm2, which is one order of magnitude larger than those in previously reported trilayer systems, resulting in the MR ratio of 2.4%. The enhanced ΔRA is considered to originate from the large spin polarization in a high-quality L21 Co2MnSi film.
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  • Magnetic Nano Structures on Solid Surfaces
    —Surface Spintronics—
    Hiroshi NAKANISHI
    2006 Volume 49 Issue 12 Pages 706-709
    Published: 2006
    Released on J-STAGE: August 09, 2007
    DOIhttps://doi.org/10.3131/jvsj.49.706
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      We have proposed the surface spintronics devices based on the magnetic nano-structures constructed on the solid surfaces. Because the Fe atom layer on Cu(111) has the spin polarized states in the surface projected bulk band gap, it is possible to make the spin conductor, spin switch and non-volatile spin memory. And we propose how to make the stable magnetic nano-structures on the reactive Si surfaces.
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  • Experiments on Nanomagnets at Surfaces
    Fumio KOMORI
    2006 Volume 49 Issue 12 Pages 710-715
    Published: 2006
    Released on J-STAGE: August 09, 2007
    DOIhttps://doi.org/10.3131/jvsj.49.710
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      Recently, ferromagnetic nanostructures have been prepared by well-controlled methods using self-organization at surfaces. Their magnetic and electronic properties are experimentally in situ studied with newly developed methods. In this article, results on the nanowires along the step edges on vicinal surfaces of nonmagnetic metals and on the regular arrays of nanodots on strain relief surface nanopatterns are reviewed. Both nanowires and nanodots show magnetic hysteresis loops as measured macroscopically by magneto-optical Kerr effect. When the magnetic nanostructure is isolated, the hysteresis is caused by the blocking of superparamagnetism at low temperatures. In the case of regular arrays of nanowires and nanodots, a long range magnetic order is established by both the percolation mechanism and the magnetic coupling among them. The microscopic interaction and the magnetic nanodomains have been clarified by spin-resolved scanning tunneling microscopy.
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  • Reactive Ion Etching of Transition-Metal Alloys
    Hiro AKINAGA, Fumiyoshi TAKANO, Shigeno MATSUMOTO, Wilson A. T. DI&Nti ...
    2006 Volume 49 Issue 12 Pages 716-721
    Published: 2006
    Released on J-STAGE: August 09, 2007
    DOIhttps://doi.org/10.3131/jvsj.49.716
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      For production of advanced spin-electronic devices, such as a magnetic random access memory with the higher-density memory cell, a reactive ion etching (RIE) process of transition metal alloys is the indispensable component of development, while no transition-metal compounds with the relatively high vapor pressure have been founded so far. Here, we show the RIE process of a NiFe thin film by using CH4:O2:NH3 discharge. The RIE process was designed by ab initio calculations, and the present result is the first successful demonstration of the chemical effect in the RIE process for transition-metal alloys. The relative etching ratio of NiFe against Ti as the metal mask was decreased by substituting CH4 with CHF3.
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  • Semiconductor Nanospintronics Devices
    Yi Kai ZHOU, Hajime ASAHI
    2006 Volume 49 Issue 12 Pages 722-727
    Published: 2006
    Released on J-STAGE: August 09, 2007
    DOIhttps://doi.org/10.3131/jvsj.49.722
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      This paper introduces the features and basic principles of the representative spintronics devices-MRAM, spin FET and circular light LED, especially which are fabricated by ferromagnetic semiconductors. It implies that the development of room temperature ferromagnetic semiconductor is very important towards the realization of semiconductor spintronics devices. The properties of transition metal (Cr) and rare-earth element (Gd) doped GaN, which show ferromagnetism at room temperature, are reviewed. The observation of TMR effect in GaCrN/AlN/GaCrN trilayer shows the possibility of GaN-based room temperature ferromagnetic semiconductor for semiconductor spintronics devices.
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Articles
  • Development of Alumina Ceramics Vacuum Chamber for J-PARC
    Michikazu KINSHO, Yoshio SAITO, Zenzaburo KABEYA, Norio OGIWARA
    2006 Volume 49 Issue 12 Pages 728-733
    Published: 2006
    Released on J-STAGE: August 09, 2007
    DOIhttps://doi.org/10.3131/jvsj.49.728
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      We successfully developed alumina ceramics vacuum chamber for the 3 GeV-RCS of J-PARC at JAEA. This chamber has titanium flanges and an outer RF shield to reduce duct impedance, and moreover TiN film is coated on the inside surface to preclude charge build up and to reduce secondary emitted electrons. The outgassing rate of the ceramics chamber measured by the conductance modulation method has a sufficiently low value of 1.2×10-8 Pa m3 s-1 m2 after 50 hours pumping. The temperature of the titanium flange became 45°C due to eddy current heating under dipole magnet operation. It was found that the radiation damage to the capacitor used for the RF shield of this duct was small, the capacitance only decreased by 7% after gamma ray irradiation of 30 MGy. In order to determine effect of the ceramics chamber on the proton beam, this ceramics chamber prepared for J-PARC was installed instead in the 12 GeV main ring at KEK-PS. The proton beam could be controlled to accelerate stably after installation, and thus it was found that this chamber did not influence the beam very much. This ceramics chamber is thus usable for the 3 GeV-RCS of J-PARC.
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  • High Power Proton Accelerator Development at KAERI and its Vacuum System
    Byung-Ho CHOI, Mi Young PARK, Kui Young KIM, Kye Ryung KIM, Jun Yeon K ...
    2006 Volume 49 Issue 12 Pages 734-738
    Published: 2006
    Released on J-STAGE: August 09, 2007
    DOIhttps://doi.org/10.3131/jvsj.49.734
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      The Proton Engineering Frontier Project (PEFP), approved and launched by the Korean government in July 2002, includes a 100 MeV proton linear accelerator (linac) development and programs for its utilization and application. The main goals in the first phase of the project, spanning from 2002 to 2005, were the design of a 100 MeV proton linac and the development of a 20 MeV linac consisting of a 50 keV proton injector, a 3 MeV radio frequency quadrupole (RFQ), and a 20 MeV drift tube linac (DTL). The 50 keV injector and 3 MeV RFQ have been installed and tested, and the 20 MeV DTL is being assembled, tuned and under a beam test. At the same time, the utilization programs using the proton beam have been planned, and some are now under way. The vacuum system of the 20 MeV proton linac and its related issues, especially in operation with a high duty, are discussed in detail.
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  • Present Status of The KEK B-Factory Vacuum System
    Yusuke SUETSUGU, Ken-ichi KANAZAWA, Shigeki KATO, Kyo SHIBATA, Hiromi ...
    2006 Volume 49 Issue 12 Pages 739-747
    Published: 2006
    Released on J-STAGE: August 09, 2007
    DOIhttps://doi.org/10.3131/jvsj.49.739
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      The KEK B-Factory (KEKB) is a two-ring electron-positron collider with asymmetric energies dedicated to proving the CP violation. The vacuum system has been working satisfactorily form the beginning of commissioning in December, 1998. The maximum stored beam currents are 1.3 A for the 8 GeV electron ring (High Energy Ring, HER), and 1.8 A for the 3.5 GeV positron ring (Low Energy Ring, LER). Most of the beam ducts are made of oxygen-free copper, owing to its ability to withstand an intense heat load and to effectively shield the radiation from high beam currents. The pumping scheme is a combination of Non-Evaporable Getter (NEG) pumps and auxiliary sputter ion pumps. An average pressure of about 1×10-7 Pa has been achieved for both rings at the maximum beam currents for both rings. The coefficient of photon-stimulated gas desorption has been decreasing steadily to less than 5×10-7 molecules photon-1 at an integrated linear photon density of about 1×1026 photons m-1. Although special care was taken to make the inside of the beam ducts as smooth as possible in order to avoid the excitation of higher order modes (HOM), the presence of high-current bunched beams has created several problems so far. The intense HOM has sometimes caused the heating of components near to some big HOM sources. Electron cloud around positron bunches led to an instability, which resulted in a vertical beam size blow-up in LER. A discussion about upgrading KEKB has just started aiming at a higher luminosity. The R & D of the vacuum components has also begun based on various experiences so far.
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  • Vacuum System Developments at the National Synchrotron Radiation Research Center -from the 1.5 GeV TLS to the 3.3 GeV TPS
    June-Rong CHEN, Gao-Yu HSIUNG, Che-Kai CHAN, Tsai-Lieh YANG, Chien-Kua ...
    2006 Volume 49 Issue 12 Pages 748-753
    Published: 2006
    Released on J-STAGE: August 09, 2007
    DOIhttps://doi.org/10.3131/jvsj.49.748
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      This article describes the design and operation of the vacuum system of the 1.5 GeV Taiwan Light Source (TLS) at the National Synchrotron Radiation Research Center (NSRRC). The TLS vacuum system has aluminum beam ducts, an oil-less fabrication process, a low impedance structure, an oil-less pumping system, little dust and an effective vacuum safety interlock system. Operating already for 12 years, TLS vacuum system has been highly reliable.
      A low-emittance 3.3 GeV synchrotron light source, the Taiwan Photon Source (TPS, with a circumference of 518.4 m), at the NSRRC is proposed to meet the requirements of advanced scientific study. Given the strictness of these requirements, the TPS vacuum system must be constructed to perform well in many areas, with a low vacuum pressure, little dust, a stable mechanical structure and a low risk of material failure caused by a high heat load or radiation damage. The vacuum system of the TPS has been preliminarily designed based on experience gained at the TLS. This work presents the technical design of the TPS vacuum chambers, the pumping configuration and some special components, emphasizing the considerations in obtaining an ultrahigh vacuum, the factors that influence beam quality and the reliability of the vacuum system.
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  • The Vacuum System for Shanghai Synchrotron Radiation Facility (SSRF)
    Dikui JIANG
    2006 Volume 49 Issue 12 Pages 754-756
    Published: 2006
    Released on J-STAGE: August 09, 2007
    DOIhttps://doi.org/10.3131/jvsj.49.754
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      SSRF is the first third generation light source in China. The storage ring vacuum system will adopt SS 316LN chambers with antechambers and discrete absorbers. Several chamber models using SS 316L were developed. There are three types of absorbers. TSP and (SIP+NEG) combined pumps will be used. A model of (SIP 2001/s+NEG WP1250) was developed. The vacuum system in total cell will be pre-baked before installing, then in-site baking will not be adopted. RF shielded bellows containing a single finger shielding structure and the high precision BPM section have been designed.
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Review
Articles
  • Structure of Platinum and Carbon Composite Thin Films Prepared by Plasma Sputtering Method
    Shigeo MATSUMOTO, Akio OKAMOTO, Toshikazu NOSAKA
    2006 Volume 49 Issue 12 Pages 763-766
    Published: 2006
    Released on J-STAGE: August 09, 2007
    DOIhttps://doi.org/10.3131/jvsj.49.763
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      Nano-particle of Pt is essential for a fabrication of high performance catalysts. It was tried to control particle size of nano-particle of Pt by preparing platinum and carbon (Pt-C) composite thin films. Pt-C composite thin films have been deposited by plasma sputtering method using methane/argon mixture gas. The sputtering voltage varied from 100 to 1000 V, the partial pressure of the methane gas varied from 0 to 1.0×10-1 Pa, the total gas pressure of the methane and argon mixture was fixed at 1.8×10-1 Pa. A high-purity platinum metal was used as a sputtering target. The electrical property of Pt-C composite thin films can be changed from metallic to dielectric according to the preparation conditions of the sputtering voltage and the partial pressure of the methane. These composite thin films have various structures, consist of nano-scale particles of Pt crystallites. The designed catalysts of the Pt-C composite thin films comprising nano Pt particles will be possibly obtained by optimizing the partial pressure of the methane and the sputtering voltage.
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  • Properties of Indium-Tin-Oxide (ITO) Films Deposited by a Facing Target Sputtering
    Satoru TAKASAWA, Sadayuki UKISHIMA, Noriaki TANI, Satoru ISHIBASHI
    2006 Volume 49 Issue 12 Pages 767-770
    Published: 2006
    Released on J-STAGE: August 09, 2007
    DOIhttps://doi.org/10.3131/jvsj.49.767
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      A facing target sputtering piece of equipment was assembled to form ITO films and compare the features with those ITO films deposited using low-voltage sputtering techniques (e.g. parallel plate magnetron sputtering). The ITO films formed using the former technique showed minimum resistance at higher oxygen partial pressure regions and exhibited generally higher resistivity than those formed using parallel plate magnetron sputtering.
      To evaluate the degree of damage caused by ITO film deposition on organic films, tris (8-hydroxyquinoline) aluminum (Alq3) was vacuum deposited on glass substrates before ITO film formation, and the photoluminescence (PL) intensity of Alq3 was compared, before and after ITO deposition. ITO film deposition using parallel plate sputtering caused 56% PL decay as compared to the reference state (before ITO film deposition), and ITO deposition using the facing target sputtering caused 36% decay, indicating the latter method was less damaging to the organic film. It also emerged that eliminating the introduction of oxygen to the facing target sputtering process could substantially suppress PL decay of the Alq3 film.
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  • Electron Emission Mechanism from the Cathode Coated with Carbon-based Hard Film
    Tatsuo IWATA, Tomomi YOSHIMOTO, Yoshio YASUMORI, Masamori IIDA
    2006 Volume 49 Issue 12 Pages 771-774
    Published: 2006
    Released on J-STAGE: August 09, 2007
    DOIhttps://doi.org/10.3131/jvsj.49.771
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      The electron emission mechanism of a cathode covered with carbon-based hard film is discussed in relation to thermionic electron emission. This new model can reproduce the frequently observed peculiar Fowler-Nordheim plots consisted of two distinct parts, which are a strong electric field dependent part and a very weak field dependent part. It is shown that there is a relationship between the threshold electric field and film thickness as well as the threshold electric field and anode-cathode distance. The present model requires neither special field-enhancement mechanisms nor extremely small work function but does require retarding potential at dielectric-film/vacuum interface (∼1 eV).
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Letters
  • Real-time Photoelectron Spectroscopy for Nitridation at Ti(0001) Surface using Supersonic N2 Molecular Beams
    Shuichi OGAWA, Yuji TAKAKUWA, Shinji ISHIDZUKA, Akitaka YOSHIGOE, Yude ...
    2006 Volume 49 Issue 12 Pages 775-779
    Published: 2006
    Released on J-STAGE: August 09, 2007
    DOIhttps://doi.org/10.3131/jvsj.49.775
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      Nitridation at a Ti(0001)-1×1 surface using supersonic N2 molecular beams was investigated by real-time photoelectron spectroscopy to clarify the adsorption reaction dynamics of N2 molecules at the Ti surface. In a whole N2 dosage region examined, N 1s spectra could be fitted well with two chemically-shifted components A and B. The binding energies were 396.9 and 396.6 eV, respectively. For both components A and B, the initial sticking probability S0, obtained by differentiating each uptake curve of N 1s, showed a decrease feature with increasing Et as the overall trend, while had significant minima at ∼0.3 and ∼1.5 eV. Such Et dependences of S0 suggest that the chemisorbed states A and B are similarly caused by a trapping-mediated adsorption process through a physisorption state at lower Et than 0.3 eV and an activated adsorption process becomes to be dominant at higher Et than 0.3 eV. Although both components A and B can appear similarly at the initial N2 adsorption stage, the component B decreases considerably after showing a maximum. The initial increase continues, however, with changing its uptake rate for the component A, indicating a change of the nitrogen adsorption state from the component B to A with progress of nitridation.
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  • Tin Oxide Thin Films Prepared by Ion Beam Induced Chemical Vapor Deposition
    Yuka FUJIKAWA, Masato KIUCHI, Takaomi MATSUTANI, Takae TAKEUCHI
    2006 Volume 49 Issue 12 Pages 780-781
    Published: 2006
    Released on J-STAGE: August 09, 2007
    DOIhttps://doi.org/10.3131/jvsj.49.780
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      We deposited transparent and electrical conductive thin films on polymer substrates ZEONOR® (cycloolefin) by oxygen ion beam induced chemical vapor deposition (IBICVD) with tetramethylstannane (TMS). The film depositions were carried out the acceleration voltage of oxygen ion beam in range from 50 to 300 eV. The deposition time was fixed at 180 minutes at all conditions. Under irradiation of 300 eV oxygen ions, the optical transmittance at 550 nm and the resistivity of the prepared film were 80% and 5.4×10-2 Ω•cm, respectively. When oxygen ion energy increased from 50 to 300 eV, root mean square of roughness and contamination of carbon were decreased.
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Conference Report
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