• Proceedings of the Zoological Society Korea Conference
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• 1999.10b
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• pp.150.2-150
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• 1999

To investigate the weathering soil buffering capacities of the artificial acidic precipitation, the weathering soils and their leachate solutions were sampled from the host rocks(granite;GR, rhyolite;RH, gabbro;GA, basalt;BA, two serpentinite;SE1, SE2 and limestone;LI) and analyzed for pH and chemical properties. 1n the soil pH of the GR and RH ,the acidic rocks, were 5.02 and 5.95, respectively. And the GA and BA, basic rocks, were 6.52 and 7.57. The SE1 and SE2 were 8.90 and 8.89. While the LI was 7.84. These results means the typical soil pH properties by host rocks. After the artificial acidic precipitation input 5OOml, the average changes of soil leachate solutions treated by pH levels(pH 5.0, 4.0 and 3.0), were pH 5.73, 5.00 and 4.40. in GR soil, and pH 6.19, 5.99 and 5.57 in RH. GA were pH 6.31, 6.04 and 5.86, BA were pH 7.05, 6.85 and 6.56 and SE1 were pH 8.31, 8.26 and 7.71. SE2 were pH 8.29, 8.24 and 7.96. LI were pH 7.55, 7.46 and 6.79. The soil leachate pHs from volcanic rocks were higher than those from the plutonic rocks and GR soils showed greater response than other soils. With increasing 100ml input-solution, the soil leachate pHs were mainly decreased. Cation concentrations, CEC, EC and total nitrogen concentrations of RH and BA soils, the volcanic rocks, were higher than those of GR and GA soil, the plutonic rocks. On the contrary, Al concentrations of the GR and GA soils were higher than those of RH and BA soils, partly because of high quartz content in GR and Al content in the biotite and plagioclase in GA.

• Journal of the Korean Vacuum Society
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• v.11 no.4
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• pp.201-206
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• 2002

Pd/Si/Pd/Ti/Au ohmic contact to n-type InGaAs was investigated with rapid thermal annealing conditions. Minimum specific contact resistivity of $3.9\times10^{-7}\Omega\textrm{cm}^2$ was achieved at $400^{\circ}C$/20sec. This was related to the formation of Pd-Si compounds by rapid thermal annealing and the in-diffusion of Si atoms to InGaAs surface. However, the specific contact resistivity increased slightly to low-$10^{-6}\Omega \textrm{cm}^2$ at $400^{\circ}C$ for longer than 30 seconds, and to high-$10^{-7}$ at 425~$450^{\circ}C$ for 10 seconds. This resulted from the formation of Pd-Ga compounds. Superior ohmic contact and non-spiking planar interface between ohmic materials and InGaAs were maintained after annealing at high temperature. Therefore, this thermally stable ohmic contact system is a promising candidate for compound semiconductor devices.

• Journal of Information Display
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• v.7 no.4
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• pp.13-16
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• 2006

II-$III_{2}-(S,Se)_{4}$ structured of phosphor have been used at various fields because they have high luminescent efficiency and broad emission band. Among these phosphors, europium doped $BaGa_{2}S_{4}$ was prepared by solid-state method. We investigated the possibility of applying [ ] due to emissive property of UV region. Also, general sulfide phosphors were synthesized by using injurious $H_{2}S$ $CS_{2}$ gas. However, this study prepared $BaGa_{2}S_{4}:Eu^{2+}$ phosphor is addition to excess sulfur under 5% $H_{2}$/95% $N_{2}$ reduction atmosphere. So, this process could involved large scale synthesis because of non-harmfulness and simple process. The photo-luminescence efficiency of the prepared $BaGa_{2}S_{4}:Eu^{2+}$ phosphor increased by 20% compared with commercial $BaGa_{2}S_{4}:Eu^{2+}$ phosphor. From this, we could conclude that the prepared $BaGa_{2}S_{4}:Eu^{2+}$ could be applied to green phosphor for white LED of three wavelengths.

• Journal of IKEEE
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• v.24 no.4
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• pp.1117-1121
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• 2020

In this work, it was confirmed that a SnO2 catalyst deposited by an atomic layer deposition(ALD) process can be employed in AlGaN/GaN heterostructure FET to detect NO2 gas. The fabricated HFET sensors on AlGaN/GaN-on-Si platform demonstrated that the devices with or without n-situ SiN have sensitivity of 5.5 % and 38 % at 200 ℃, respectively with response to 100 ppm-NO2.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.144-145
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• 2009

Single crystal $CdGa_2Se_4$ layers were grown on a thoroughly etched semi-insulating GaAs(100) substrate at $420^{\circ}C$ with the hot wall epitaxy (HWE) system by evaporating the poly crystal source of $CdGa_2Se_4$ at $630\;^{\circ}C$. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of single crystal $CdGa_2Se_4$ thin films measured with Hall effect by van der Pauw method are $8.27\;\times\;10^{17}\;cm^{-3}$, $345\;cm^2/V{\cdot}s$ at 293 K, respectively. The photocurrent and the absorption spectra of $CdGa_2Se_4$/SI(Semi-Insulated) GaAs(100) are measured ranging from 293 K to 10K. The temperature dependence of the energy band gap of the $CdGa_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g$(T) = 2.6400 eV - ($7.721\;{\times}\;10^{-4}\;eV/K)T^2$/(T + 399 K). Using the photocurrent spectra and the Hopfield quasi cubic model, the crystal field energy(${\Delta}cr$) and the spin-orbit splitting energy(${\Delta}so$) for the valence band of the $CdGa_2Se_4$ have been estimated to be 106.5 meV and 418.9 meV at 10 K, respectively. The three photocurrent peaks observed at 10 K are ascribed to the $A_1$-, $B_1$-, and $C_{11}$-exciton peaks.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.7
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• pp.610-614
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• 2008

In this work, the electrical and optical properties of the two different p-type GaN electrode schemes, ZnNi/ITO and ZnNi/Au, were compared each other, and applied to the top-emitting GaN/InGaN light-emitting diodes (LEDs). The ZnNi/ITO electrode showed much higher transmittance (90%) and slightly lower contact resistance $(1.27{\times}10^{-4}{\Omega}cm^2)$ than those (77%, $(2.26{\times}10^{-4}{\Omega}cm^2)$) of the ZnNi/Au at a wavelength of 460 nm. In addition, GaN LEDs having ZnNi/ITO showed accordingly higher light output power and luminous intensity than those having ZnNI/Au did at the current levels up to 1 A.

• Proceedings of the KIEE Conference
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• 2000.07e
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• pp.56-59
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• 2000

$CdGaInS_4$ and $CdGaInS_4:Er^{3+}$ single crystals crystallized in the rhombohedral(hexagonal) structure. with lattice constants $a=3.913{\AA},\;c=37.245{\AA}$ for $CdGaInS_4$, and $a=3.899{\AA}$ and $c=36.970{\AA}$ for $CdGaInS_4:Er^{3+}$. The optical absorption measured near the fundamental band edge showed that the optical energy band structure of these compounds had a direct and indirect band gap. the direct and indirect energy gaps are found to be 2.771 and 2.503 eV for $CdGaInS_4$, and 2.665 and 2.479 eV for $CdGaInS_4:Er^{3+}$ at 10 K. The temperature dependence of the optical energy gap was well represented by the Varshni equation. In $CdGaInS_4$, the values of ${\alpha},\;{\beta}$ of the direct and the indirect energy gap were found to be $7.57{\times}10^{-4}eV/K$. $6.53{\times}10^{-4}eV/K$ and 240K. 197K. and the values of ${\alpha}$ and ${\beta}$ of the direct and the indirect energy gap in the $CdGaInS_4:Er^{3+}$ were given by $8.28{\times}10^{-4}eV/K,\;2.08{\times}10^{-4}eV/K$ and 425 K, 283 K, respectively.

• Journal of the Korean Ceramic Society
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• v.39 no.4
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• pp.352-358
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• 2002

The variations of the properties of Sr and Mg added $LaGaO_3$ system electrolyte with the amount of the additive and the sintering condition were studied. Main phase was (La$_{1-x}Sr_x)(Ga_{1-y}Mg_y)O_{3-\delta}$ phase for each compositions and the single phases $(La_{0.85}Sr_{0.15})(Ga_{0.85}Mg_{0.15})O_{3-\delta},(La_{0.85}Sr_{0.15})(Ga_{0.8}Mg_{0.2})O_{3-\delta}$ and $(La_{0.8}Sr_{0.2})(Ga_{0.8}Mg_{0.2})O{3-\delta}$ were obtained with the decrease in the sintering temperature and Mg addition. Thermal expansion coefficient of the $(La_{0.8}Sr_{0.2})(Ga_{0.8}Mg_{0.2})O_{3-\delta}$ decreased with the increase in the sintering temperature. Electric conductivity of electrolyte sintered at $1500^{circ}C$ for 1h was 0.14 S/cm at $800^{circ}C$ with 1 mA.

• Korean Journal of Crystallography
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• v.11 no.1
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• pp.46-51
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• 2000

The molecular structures of 2-SC₄H₃CH=NN(H)C/sub 6/H/sub 5/(C/sub 11/H/sub 10/N₂S) and (GaMe₂)₂(2-SC₄H₃CH=NNC/sub 6/H/sub 5/)₂(C/sub 26/H/sub 30/Ga₂N₄S₂) have been determined by X-ray diffraction. Crystallographic data for 2-SC₄H₃CH=NN(H)C/sub 6/H/sub 5/:orthorhombic space group P2₁2₁2₁, a=6.108(1)Å, b=7.593(1)Å, c=22.356(2)Å, V=1037.1(3)ų, Z=4, R=0.0613. Crystallographic data for (GaMe₂)₂(2-SC₄H₃CH=NNC/sub 6/H/sub 5/)₂:monoclinic space group P2₁/n, a=15.996(2) Å, c=9.879(3)Å, β=100.07.(2)°, V=2764.599)ų, Z=4, R=0.0503.

• Korean Journal of Materials Research
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• v.7 no.8
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• pp.707-713
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• 1997

HVPE(hydride vapor phase epitaxy)법으로 (111)MgAI$_{2}$ $O_{4}$기판위에 GaN 후막을 성장하였다. GaN를 성장하기 전에 기판에 표면을 GaCI로 처리한 수 성장하였을 때 이중 X선 회절 피크의 반치폭이 710 arcsec로서 N $H_{3}$로 처리한 후 성장한 GaN에 비하여 작았으며, 무색 투명의 경면상태가 얻어\ulcorner다. 113$0^{\circ}C$의 온도에서 성장한 GaN 의 광루미네센스(PL)특성과 동일하게 나타났다. 10K의 온도에서 측정된 PL 스펙트럼은 자유여기자와 속박여기자의 재결합천이에 의한 피크들과 Mg과 관련된 도너-억셉터 쌍 사이의 재결합 및 이의 1LO, 2LO, 3LO 및 4 LO 포논복제에 의한 피크들이 나타났다. 성장된 GaN는 n형의 전도성을나타내었으며, 캐리어 이동도와 농도는 각각 21.3$\textrm{cm}^2$/V ㆍsec와 4.2 x $10^{18}$$cm^{-3}$이었다.