• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.7
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• pp.486-493
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• 2003

Schottky type A $l_{0.33}$G $a_{0.67}$N ultraviolet photodetectors were fabricated on the MOCVD grown AlGaN/ $n^{＋}$-GaN and AlGaN/AlGaN interlayer/ $n^{＋}$-GaN structures. The grown layers have the carrier concentrations of -$10^{18}$, and the mobilities were 236 and 269 $\textrm{cm}^2$/V.s, respectively. After mesa etching by ICP etching system, the Si3N4 layer was deposited for passivation between the contacts and Ti/AL/Ni/Au and Pt were deposited for ohmic and Schottky contact, respectively. The fabricated Pt/A $l_{0.33}$G $a_{0.67}$N Schottky diode revealed a leakage current of 1 nA for samples with interlayer and 0.1$\mu\textrm{A}$ for samples without interlayer at a reverse bias of -5 V. In optical measurement, the Pt/A $l_{0.33}$G $a_{0.67}$N diode with interlayer showed a cut-off wavelength of 300 nm, a prominent responsivity of 0.15 A/W at 280 nm and a UV-visible extinction ratio of 1.5x$10^4./TEX>.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.2
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• pp.43-48
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• 2017

Conductive $Sn_xO_y$ thin films were fabricated via RF reactive sputtering using SnO:Sn (80:20 mol%) composite target. The composite target was used to produce a chemically stable composition of $Sn_xO_y$ thin film while controlling structural defects by chemical reaction between tin and oxygen. During sputtering pressure, RF power, and substrate temperature were fixed, and oxygen partial pressure was varied from 0% to 12%. Annealing process was carried out at $300^{\circ}C$ for 1 hour in vacuum. Except $P_{O2}=0%$ sample, all samples showed the transmittance of 80~90% and amorphous phase before and after annealing. Electrically stable p-type $Sn_xO_y$ thin film with high transmittance was only obtained from the oxygen partial pressure at 12%. The carrier concentration and mobility for the $P_{O2}=12%$ were $6.36{\times}10^{18}cm^{-3}$ and $1.02cm^2V^{-1}s^{-1}$ respectively after annealing.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.231-237
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• 2005

The sizes and structure of micelles and vesicles formed in ammonium dodecyl sulfate (ADS)/octadecyl trimethyl ammonium chloride (OTAC) mixed aqueous solutions were analyzed by small-angle neutron scattering. In micellar regions of pure ADS and OTAC aqueous solution, the spherical micelles were formed at given concentrations and their sizes were 40 and $61{\AA}$, respectively. The structure transition of pure micelles occurred above 300 mM due to the constancy of the intermicellar distance above 250 mM. The coexisting region of mixed micelles and vesicles in phase diagram of mixed system was also assured. It was investigated that vesicle formed spontaneously took a bilayer structure. The lamellar thickness of vesicles decreased with increasing concentration of vesicle samples. However, the size could not be determined for mixed micelle and vesicle above 100 nm due to limitation of low q ranges. Finally, The 9 mM solution of ADS mole fraction 0.9 (${\alpha}$=0.9) showed bilayer structure compared to phase diagram classified into mixed micelle.

• Journal of Korean Society of Forest Science
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• v.100 no.3
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• pp.466-475
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• 2011

This study purposed to analyze the spatial pattern and the amount of carbon emission at the deforestation area based on the administrative and GIS data. The total size of deforestation area in last nine years (2000-2008) was about 649 ha, and it was occurred annually about 72 ha. The occurrence rate of deforestation per administrative area in Wonju was about 0.74%. It was 0.34% higher than that of Kwangwondo, and 0.06% less than that of National rate. On the other hand, the forms of deforestation by purpose were not related to the administrative district unit. The number of deforestation forms was highest at settlements. second most frequent form is other land. Grassland showed the lowest score. In addition, the deforestations were more occurred which is closed to the existing housing and building rather than roads. The number of deforestation was 1.2 times higher based on 300m. Seventy percent of deforestation was occurred which is less than 0.5 ha in size, and it increased to 91% when the size is less than 1ha. The total size of theoretical carbon emission based on deforestation area was estimated at 23,424 tc, and average annual carbon emission was estimated by 2,603 tc. Carbon emission per ha was 36.1 tC/ha. This study results will be useful to construct the greenhouse gas statistical verification system against the Post-2012 by GIS.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.4
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• pp.235-243
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• 2016

Korea is part of a region of low to moderate seismicity located inside the Eurasian plate with bedrock located at depths less than 30 m. However, the spectral acceleration obtained from site response analyses based on the geologic conditions of inland areas of the Korean peninsula are significantly different from the current Korean seismic code. Therefore, suitable site classification scheme and design response spectra based on local site conditions in the Korean peninsula are required to produce reliable estimates of earthquake ground motion. In this study, site-specific response analyses were performed at more than 300 sites with at least 100 sites at each site categories of $S_C$, $S_D$, and $S_E$ as defined in the current seismic code in Korea. The process of creating a huge database of input parameters - such as shear wave velocity profiles, normalized shear modulus reduction curves, damping curves, and input earthquake motions - for site response analyses were described. The response spectra and site coefficients obtained from site response analyses were compared with those proposed for the site categories in the current code. Problems with the current seismic design code were subsequently discussed, and the development and verifications of new site classification system and corresponding design response spectra are detailed in companion papers (II-development of new site categories and design response spectra and III-Verifications)

• Journal of the Microelectronics and Packaging Society
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• v.11 no.3 s.32
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• pp.47-53
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• 2004

Eutectic Au-20Sn(compositions are all in weight percent unless specified otherwise) solder alloys were soldered on the Ni substrate with various time and temperature. The composition, phase identification and morphology of intermetallic compounds(IMC) at the interface were examined using Scanning Electron Microscopy(SEM). There were two types of IMCs, $(Au,Ni)_3Sn_2$ and $(Au,Ni)_3Sn$ at the interface. The transition in morphology of $(Au,Ni)_3Sn_2$ has been observed at $300{\~}400^{\circ}C$. The morphology transition of $(Au,Ni)_3Sn_2$ is due to the decrease of enthalpy of formation of $(Au,Ni)_3Sn_2$ phase and has been explained well by Jackson's parameter with temperature. Because the number of diffusion channel is different at each soldering temperature, IMC thickness is nearly same at all temperature.

• Proceedings of the Korean Vacuum Society Conference
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• 1996.06a
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• pp.40-41
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• 1996

Nitridation technique has been receiving much attention for the formation of a thin nitrided buffer layer on which high quality nitride films can be formedl. Particularly, gallium nitride (GaN) has been considered as a promising material for blue-and ultraviolet-emitting devices. It can also be used for in situ formed and stable passivation layers for selective growth of $GaAs_2$. In this work, formation of a thin nitrided layer is investigated. Nitrogen electron cyclotron resonance(ECR)-plasma is employed for the formation of thin nitrided layer. The plasma source used in this work is a compact ECR plasma gun3 which is specifically designed to enhance control, and to provide in-situ monitoring of plasma parameters during plasma-assisted processing. Microwave power of 100-200 W was used to excite the plasma which was emitted from an orifice of 25 rnm in diameter. The substrate were positioned 15 em away from the orifice of plasma source. Prior to nitridation is performed, the surface of n-type (001)GaAs was exposed to hydrogen plasma for 20 min at $300{\;}^{\circ}C$ in order to eliminate a native oxide formed on GaAs surface. Change from ring to streak in RHEED pattern can be obtained through the irradiation of hydrogen plasma, indicating a clean surface. Nitridation was carried out for 5-40 min at $RT-600{\;}^{\circ}C$ in a ECR plasma-assisted molecular beam epitaxy system. Typical chamber pressure was $7.5{\times}lO^{-4}$ Torr during the nitridations at $N_2$ flow rate of 10 seem.(omitted)mitted)

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1352-1354
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• 1998

$LiNbO_3$ transistor showed relatively stable characteristic, low interface trap density, and large remanent polarization. This paper reports ferroelectric $LiNbO_3$ thin films grown directly on p-type Si(100) substrates by 13.56 MHz rf magnetron sputtering system for FRAM applications. To take advantage of low temperature requirement for growing films, we deposited $LiNbO_3$ films lower than $300 ^{\circ}C$. RTA(Rapid Thermal Anneal) treatment was performed for as-deposited films in an oxygen atmosphere at $600^{\circ}C$ for 60 sec. We learned from X-ray diffraction that the RTA annealed films were changed from amorphous to poly-crystalline $LiNbO_3$ which exhibited (012), (015), and (022) orientations. The I-V characteristics of $LiNbO_3$ films before and after anneal treatment showed that RTA improved the leakage current of films. The leakage current density of films decreased from $10^{-5}$ to $10^{-7} A/cm^2$ at room temperature measurement. Breakdown electric field of the films exhibited higher than 500 kV/cm. The C-V curves showed the clockwise hysteresis represents ferroelectric switching characteristics. From C-V curves, we calculated dielectric constant of thin film $LiNbO_3$ as 27.5 which is close to that of bulk value.

• Applied Biological Chemistry
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• v.23 no.4
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• pp.199-205
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• 1980

Relatively large quantity of the major components of saponin, $ginsenoside-Rb_1,\;-Rb_2,\;-Rc,\;-Rd,\;-Re\;and\;-Rg_1$ from Panax ginseng C.A. Meyer were isolated using preparative and semipreparative high performance liquid chromatography, and analyzed by analytical HPLC. The application of HPLC for isolation of ginsenosides was not only very effective for rapid analysis but also reduced the isolation time. The isolation capacity of pure ginsenosides was $30{\sim}50mg/hr$.

• Bulletin of the Korean Chemical Society
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• v.17 no.1
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• pp.46-50
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• 1996

Monoanionic nickel(Ⅲ) complexes, [Ni(dmbit)2]1- and [Ni(dmbbip)2]1- where dmbit2- and dmbbip2- denote 2-thiobenzo[d]-1,3-dithiole-5,6-dithiolate and 1,2-bis(isopropylthio)benzen-4,5-dithiolate, respectively, have been synthesized by the iodine oxidation of dianionic complexes. In the scanning electron microscopic(SEM) images, these complexes show the well-grown two-dimensional layered structures which are clearly comparable to the dianionic ones with three-dimensional structures. Magnetic susceptibilities of nickel(Ⅲ)complexes are fitted well with the two-dimensional Heisenberg antiferromagnet model of S=1/2 system resulting in the spin-exchange parameters (|J|/k) of 11.4 K and 0.45 K, respectively. The weaker magnetic interaction in [Ni(dmbbip)2]1- is resulted from the bulky isopropyl groups on the periphery of dmbbip ligand. EPR measurements for [Ni(dmbit)2]1- give the signal with axial symmetry and the anisotropic g-values for low-spin nickel(Ⅲ) (g//=2.158, g =2.030,gav=2.074 at 300 K; g//=2.162, g =2.038, gav=2.080 at 77 K). It is therefore concluded that nickel(Ⅱ) is oxidized to nickel(Ⅲ), rather than dmbit2- and dmbbip2- ligands are, by the iodine oxidation. The paramagnetic Ni(Ⅲ) would be located in the axial symmetry(D4h) with the electronic configuration of (dxz2dyz2dz22dxy1dx2-y20).