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pISSN : 1225-1429 / eISSN : 2234-5078

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2004, Vol.14, No.1

  • 1.

    Growth of nickel-catalyzed carbon nanofibers using MPCVD method and their electrical properties

    Kim Sung-Hoon | 2004, 14(1) | pp.1~5 | number of Cited : 0
    Abstract PDF
    Carbon nanofilaments were formed on silicon substrate via microwave plasma-enhanced chemical vapor deposition method. The structure of carbon nanofilaments was identified as the carbon nanofibers. The extent of carbon nanofibers growth and the diameters of carbon nanofibers increased with increasing the total pressure. The growth direction of carbon nanofibers was horizontal to the substrate. Laterally grown carbon nanofibers showed the semiconductor electrical characteristics.
  • 2.

    The formation of diamond films on high speed steel with a titanium interlayer by electron-assisted CVD process

    정연진 | 이건영 | 이호진 and 1other persons | 2004, 14(1) | pp.6~11 | number of Cited : 0
    Abstract PDF
    The characteristics of interface layer and the effect of bias voltages on the nucleation density and hetroepitaxial growth of diamond films were studied in the hot filament CVD diamond process. Diamond films were deposited on a high speed steel (SKH-51) substrate by bias-assisted hot filament CVD technique with a titanium interlayer. The bias applied for enhancing the emission of electrons from the filament increased the nucleation density and achieving heteroepitaxial growth of CVD diamond. Diamond films obtained at a gas pressure of 20 torr; a bias voltage of 200 V and a substrate temperature of 700oC. Titanium was a suitable element as an interlayer for the diamond deposition on steel because it has high diffusivity of Fe and C as a carbide forming element.
  • 3.

    A study on crystal growth and properties of high quality DAST

    윤선웅 | YON SEOG JOO | 김종흠 | 2004, 14(1) | pp.12~16 | number of Cited : 0
    Abstract PDF
    Abstract In this study, we have investigated the development of the crystal growth stability and reproducibility for large and high-quality DAST. DAST crystal were grown from a saturated methanol solution by a slow cooling method and DAST was synthesized by the condensation of 4-methyl-n-methyl pyridinum tosylate, which was prepared from 4-pocoline and methyl toluenesulponate and 4-N-dimethyl amino-bezaldehyde in the presence of piperidine. We had synthesized DAST crystals in dry Argon atmosphere in order to avoid the formation of hydride organge co-crystals, DAST·H2O. Since DAST molecules crystallize in a humid atmosphere, crystal structure become centrosymmetric, and then second order NLO (nonlinear optical) properties would be disappeared. We fixed the growth orientation of DAST crystal (001) surface. The crystal growth was proceeded at a cooling rate of 1oC/day and the cooling period is for 4 days. The dimensions of seed crystal was 2.5×3.6×0.4 mm3 and we have obtained a DAST crystal with the dimension of 10×10.5×3.0 mm3. The color of grown DAST crystal is red and it’s surface appears to be metallic green.
  • 4.

    Theory of specific heat discontinuity of the superconductor under applied magnetic field

    Eo ik-soo | 김철호 | 2004, 14(1) | pp.17~20 | number of Cited : 2
    Abstract PDF
    We derive specific heat gap at the critical temperature as an exact anylitical function of applied magnetic field by using the thermodynamics. And we calculate numerical value of specific heat gap for some superconductors with the derived results and discuss the physical meaning. And it will be discussed that gap of specific heat discontinuity under certain magnetic field intensity become zero at the critical temperature
  • 5.

    A study on the identification of type Ⅱa natural diamonds treated by the HPHT method

    Kim, Young-chool | Choi, Hyun-min | 2004, 14(1) | pp.21~26 | number of Cited : 1
    Abstract PDF
    Results from PL and Raman spectroscopic analyses of HPHT (high-pressure high-temperature) treated type IIa diamonds are presented, and these spectral characteristics are compared with those of untreated diamonds of similar color and type. We identify a number of significant changes by 325 nm He/Cd laser excitation. Several peaks are removed completely, including H4, H3 system in HPHT treated diamond. The N3 system, however, increased in emission. Also we can find the behaviour of the nitrogen-vacancy related center N-V centers at 575 and 637.1 nm, as observed with 514 nm Ar ion laser excitation. When these centers are present, the FWHM (full width at half maximum) of 637.1 nm luminescence intensities offers a potential means of separating HPHT-treated from untreated typeIIa diamonds. The width of 637.1 nm (N-V)- line measured at the position of half the peak’s height are determine to range from 19.8 to 32.1 cm-1 for HPHT treated diamonds.
  • 6.

    Bonding structure of the DLC films deposited by RF-PECVD

    Bonggeun Choi | 신재혁 | 안종일 and 1other persons | 2004, 14(1) | pp.27~32 | number of Cited : 1
    Abstract PDF
    Amorphous GaN film was deposited using a laser ablation of the highly densified GaN target. Through the surface morphological and compositional analysis of films deposited under various laser energies and Ar gas pressures, the film deposited under the pressure of 10 Pa were found to be amorphous GaN with the smooth surface. In particular, the film at 200 mJ/pulse showed the enhanced crystallinity and stoichiometric composition, compared with those of the films at relatively lower laser energy. The strong band-gap emission at 2.8 eV was observed from amorphous GaN film in the room temperature photoluminescence spectra, showing the highest efficiency in the film at 200 mJ/pulse under 10 Pa.
  • 7.

    Growth and characterization of amorphous GaN film using a pulsed-laser ablation

    심승환 | 윤종원 | Naoto koshizaki and 1other persons | 2004, 14(1) | pp.33~36 | number of Cited : 0
    Abstract PDF
    Amorphous GaN film was deposited using a laser ablation of the highly densified GaN target. Through the surface morphological and compositional analysis of films deposited under various laser energies and Ar gas pressures, the film deposited under the pressure of 10 Pa were found to be amorphous GaN with the smooth surface. In particular, the film at 200 mJ/pulse showed the enhanced crystallinity and stoichiometric composition, compared with those of the films at relatively lower laser energy. The strong band-gap emission at 2.8 eV was observed from amorphous GaN film in the room temperature photoluminescence spectra, showing the highest efficiency in the film at 200 mJ/pulse under 10 Pa.