Shinku
Online ISSN : 1880-9413
Print ISSN : 0559-8516
ISSN-L : 0559-8516
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Volume 48, Issue 7
Displaying 1-12 of 12 articles from this issue
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Special Issue: Study on Metastable Atoms
Reviews
Regular Papers
Letters
  • Study of Spin Tunnel Junctions using AlOx Insulating Barrier Fabricated by Reactive Sputtering
    Shinya HARADA, Kazuo SHIIKI
    2005 Volume 48 Issue 7 Pages 436-438
    Published: 2005
    Released on J-STAGE: August 11, 2006
    DOIhttps://doi.org/10.3131/jvsj.48.436
    JOURNAL FREE ACCESS
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    The spin tunnel junctions (STJ) using AlOx insulating barrier layer has been investigated and its composition and electrical characteristic are discussed. The AlOx insulating barrier layer was fabricated by ion-beam-sputtering Al with oxygen ions accelerated from assist gun. The barrier height was determined by measuring the current-voltage characteristic of Co (10 nm)/AlOx/Co (50 nm) STJ and fitting the current-voltage curve by Simmons' fitting. It is revealed that varying the oxygen gas flow at the assist gun changed the composition of AlOx and insulating layer characteristics, which can be explained by Anderson's model. The barrier height also depended on the sputtering time. Furthermore, the noise of STJ fabricated by this method was lower than the noise of STJ using insulating barrier layer fabricated by natural oxidization. From these experimental results, It is expected that by optimizing the oxygen gas flow at the assist gun and the sputtering time, we can obtain Co/AlOx/Co STJ with high magnetoresistance ratio and low noise.
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  • Microcrystallization of Amorphous GeC:H Films Prepared by Reactive Sputtering
    Nobuo SAITO, Hiromu IWATA, Isamu NAKAAKI, Osamu SUGIYAMA, Tomuo YAMAGU ...
    2005 Volume 48 Issue 7 Pages 439-441
    Published: 2005
    Released on J-STAGE: August 11, 2006
    DOIhttps://doi.org/10.3131/jvsj.48.439
    JOURNAL FREE ACCESS
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    GeC:H films have been deposited by a reactive rf magnetron sputtering of Ge target in argon-methane and helium gas mixtures. The effect of helium partial pressure ratio R on the structural, optical and electrical properties of the films was investigated. The films shows the amorphous nature in the low R range up to 60%. With increasing R above 70%, the peak of X-ray diffraction appears, the bonding configuration concerning carbon bonds in IR spectra increases, the optical bandgap decreases, and the dark conductivity increases rapidly. It is found from these data that the microcrystallization of GeC:H films could be achieved by introducing hellium in the sputtering process.
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  • Effect of Annealing on Slightly Oxidized Silicon Surface
    Masashi KAKIMOTO, Yuichi SANO, Yoshitomo KAMIURA, Yusuke MIZOKAWA
    2005 Volume 48 Issue 7 Pages 442-444
    Published: 2005
    Released on J-STAGE: August 11, 2006
    DOIhttps://doi.org/10.3131/jvsj.48.442
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    We investigated the effect of annealing on slightly oxidized silicon surfaces by using atomic force microscopy (AFM), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The very thin oxide films (∼1 nm) were made by chemical treatment for three kinds of samples. One of them was p-type Si(100) wafer, the others were heavily phosphorus-doped Si(100) wafers made by ion implantation and low pressure chemical vapor deposition. These samples were annealed at low temperature (700°C∼900°C) in ultra high vacuum. AFM measurements showed that RMS roughness of all surfaces after annealing in UHV was several times as much as that of the surfaces right after chemical treatment. The morphology of every sample after oxide silicon desorbed by annealing revealed dot shape. And the morphology of p-type Si(100) after annealing at 730°C resembled that of heavily phosphorus-doped Si(100) made by ion implantation after annealing at 830°C. AES and XPS measurements showed that the difference of annealing temperature for these samples was due to the difference of their oxide thickness and the quality of their oxides.
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  • Effect of Surface Roughness on Adsorption Force and Smooth Sliding in a Vacuum
    Akira KASAHARA, Masahiro GOTO, Testuo OISHI, Masahiro TOSA
    2005 Volume 48 Issue 7 Pages 445-447
    Published: 2005
    Released on J-STAGE: August 11, 2006
    DOIhttps://doi.org/10.3131/jvsj.48.445
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    We evaluated the sliding friction coefficient under changes of load from 0.98 mN to 196 mN at pressures of 105 Pa and 10-5 Pa. The friction of type 304 austenitic stainless steels as typical vacuum materials was measured, and surface roughness of nano order was prepared by electrochemical buffing and chemical etching. The same value of friction coefficient on samples measured in a vacuum as at atmospheric pressure when surface roughness was prepared to about 40 nm to 1.2 μm was also found. There is an absorption force of about 20 mN on a sample with a surface roughness of less than about 670 nm at atmospheric pressure. In a vacuum, a sample with a surface roughness under 40 nm also showed adsorption force below 0.98 mN, while a sample with a surface roughness around 100 nm showed higher adsorption force of about 15 mN. It was concluded that there was a range of surface roughnesses without any decrease in adsorption force even in a vacuum.
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  • Hydrogen Gas Sensing using Two Type of Pressure Gauges
    Atsushi SUZUKI, Akira KUROKAWA, Hidehiko NONAKA, Shingo ICHIMURA
    2005 Volume 48 Issue 7 Pages 448-450
    Published: 2005
    Released on J-STAGE: August 11, 2006
    DOIhttps://doi.org/10.3131/jvsj.48.448
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    For safety hydrogen sensing, the pressure measurement with a capacitance manometer and a quartz friction pressure gauge (Q-gauge) were investigated. Q-gauge pressure reading decreases when hydrogen gas is introduced into air supplied from atmosphere without any change of pressure measured by a capacitance manometer. This result indicates that the present pressure measurement using two pressure gauges is possible to detect the hydrogen leakage into air. In addition, a decrease of Q-gauge pressure reading correlates with a flow rate of the hydrogen gas, and increases with hydrogen concentration in air. Then it was shown that the low detection limit of hydrogen concentration is below 1%. Response time for hydrogen introduction is faster than 30 seconds, which meets the requirements for the hydrogen gas leak sensor. As above, the present safe pressure measurement using a capacitance manometer and a Q-gauge is satisfactorily useful for the hydrogen gas leak sensing.
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