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Surface Characterization of Mo Oxynitride Films Obtained by RF Sputtering at Various N2 Ratios
Juyun Park,강용철 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.1
Molybdenum oxynitride (MoNxOy) thin films were deposited on p-type Si(100) wafer by rf magnetron sputtering method at various nitrogen gas ratios. The surface characteristics of deposited thin films were investigated using scanning electron microscopy, atomic force microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The thickness of films decreased down to 70 from 1000 nm and the roughness was varied with increasing N2 gas ratio. The formation of MoNxOy was confirmed by existence of Mo species between Moδ+ and Mo5+ oxidation state and ON bond in XP spectra. At 0% of N2 gas ratio, metallic simple cubic Mo structure was observed. As the N2 gas ratio increased, Mo nitrate and Mo silicate phases were appeared.
Juyun Park,Rex D. Ramsier,Kyounga Lim,강용철 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.9
Copper oxide thin films were synthesized by reactive radio frequency magnetron sputtering at different oxygen gas ratios. The chemical and physical properties of the thin films were investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). XPS results revealed that the dominant oxidation states of Cu were Cu^0 and Cu^+ at 0%oxygen ratio. When the oxygen ratios increased above 5%, Cu was oxidized as CuO as detected by X-ray induced Auger electron spectroscopy and the Cu(OH)_2 phase was confirmed independent of the oxygen ratio. The valence band maxima were 1.19 ± 0.09 eV and an increase in the density of states was confirmed after formation of CuO. The thickness and roughness of copper oxide thin films decreased with increasing oxygen ratio. The crystallinity of the copper oxide films changed from cubic Cu through cubic Cu2_O to monoclinic CuO with mean crystallite sizes of 8.8 nm (Cu) and 16.9 nm (CuO) at the 10% oxygen ratio level.
Surface Phenomena of Deuterized Ethanol Exposed Zircaloy-4 Surfaces
Juyun Park,Se-Won Jung,Mi-Sun Chun,Yong-Cheol Kang 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.6
We report the results of the surface chemistry of deuterized ethanol exposed Zircaloy-4 (Zry-4) surfaces with various amount of C2D5OD exposures at 190 K. This system was examined with Auger electron spectroscopy (AES) and temperature programmed desorption (TPD) techniques. In TPD study, D2 was evolved at two different desorption temperature regions accompanying with broad desorption background. The lower temperature feature at around 520 K showed first-order desorption kinetics. The high temperature desorption peak at around 650 K shifted to lower desorption temperature as the exposure of C2D5OD increased. The Zr(MNV) Auger peak shifted about 2.5 eV from 147 eV to lower electron energy followed by 300 L of C2D5OD dosing. This implies metallic zirconium was oxidized by deuterized ethanol adsorption. After stepwise annealing of the oxidized Zry-4 sample up to 843 K, the shifted Zr(MNV) peak was gradually shifted back to metallic zirconium peak position. After the sample was heated to 843 K, the oxygen content near the Zry-4 surface was recovered to clean surface level. The concentration of carbon, however, was not recovered by annealing the sample.
Generation of 1.5 cycle 0.3 TW laser pulses using a hollow-fiber pulse compressor.
Park, Juyun,Lee, Jae-Hwan,Nam, Chang Hee Optical Society of America 2009 Optics letters Vol.34 No.15
<P>Pulse compression in a differentially pumped neon-filled hollow fiber was used to generate high-power few-cycle laser pulses. The pulse compression process was optimized by adjusting gas pressure and laser chirp to produce the shortest laser pulses. Precise dispersion control enabled the generation of laser pulses with duration of 3.7 fs and energy of 1.2 mJ. This corresponds to an output of 1.5 cycle, 0.3 TW pulses at a 1 kHz repetition rate using positively chirped 33 fs laser pulses.</P>
Characterization of Nickel Oxide Nanofibers Obtained by Electrospinning
Park, Juyun,Kang, Yong-Cheol,Koh, Sung Wi The Basic Science Institute Chosun University 2018 조선자연과학논문집 Vol.11 No.1
Nickel oxide nanofibers were synthesized by electrospinning with nickel(II) acetate tetrahydrate and polyvinylpyrrolidone and calcination process. The nanofiber shape was easily detected from the nanofibers with high Ni contents after calcined at $600^{\circ}C$ and the crystal structure of layer-by-layer growth was observed from SEM images at $900^{\circ}C$. XRD and TEM results showed metallic Ni and NiO structure were formed at nanofibers obtained at 600 and $900^{\circ}C$ and the crystallite size was calculated from 25 to 55 nm. The surface of nanofibers was fully oxidized from the deconvoluted Cu 2p and O 1s XPS spectra.
Soft x-ray microscope constructed with a PMMA phase-reversal zone plate.
Park, Jong Ju,Kim, Deuk Su,Jeon, Sang Chul,Park, Juyun,Lee, Kyoung Hwan,Lee, Jae-hwan,Kim, Ki Nam,Yoo, Jung Jae,Nam, Chang Hee Optical Society of America 2009 Optics letters Vol.34 No.3
<P>A soft x-ray microscope based on a phase-reversal zone plate was constructed and tested using high harmonic radiation as a coherent light source. The 61st harmonic centered at 13.3 nm was optimized in spectral sharpness and intensity by controlling the incident laser energy and chirp. A phase-reversal zone plate made of polymethyl methacrylate more than doubled the first-order efficiency. The nano patterns, imaged on an x-ray CCD with a magnification of 650, showed that the measured resolution of the microscope was better than 100 nm.</P>
The Properties of RF Sputtered Zirconium Oxide Thin Films at Different Plasma Gas Ratio
Juyun Park,,Jin Kook Heo,Yong-Cheol Kang 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.2
Zirconium oxide thin films deposited on the p-type Si(100) substrates by radio-frequency (RF) reactive magnetron sputtering with different plasma gas ratios have been studied by using spectroscopic ellipsometry (SE), atomic force microscopy (AFM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The deposition of the films was monitored by the oxygen gas ratio which has been increased from 0 to 80%. We found that the thickness and roughness of the zirconium oxide thin films are relatively constant. The XRD revealed that the deposited thin films have polycrystalline phases, Zr(101) and monoclinic ZrO2 (131). The XPS result showed that the oxidation states of zirconium suboxides were changed to zirconia form with increasing O2 gas ratio.