• Korean Journal of Materials Research
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• v.30 no.8
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• pp.413-420
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• 2020

Lu₃Al_5-xGa_xO₁₂:Ce³⁺,Cr³⁺ powders are prepared using a solid-state reaction method. To determine the crystal structure, Rietveld refinement is performed. The results indicate that Ga³⁺ ions preferentially occupied tetrahedral rather than octahedral sites. The lattice constant linearly increases, obeying Vegard's law, despite the strong preference of Ga³⁺ for the tetrahedral sites. Increasing x led to a blue-shift of the Ce³⁺ emission band in the green region and a change in the emission intensity. Persistent luminescence is observed from the powders prepared with x = 2-3, occurring through a trapping and detrapping process between Ce³⁺ and Cr³⁺ ions. The longest persistent luminescence is achieved for x = 2; its lifetime is at least 30 min. The findings are explained using crystal structure refinement, crystal field splitting, optical band gap, and electron trapping mechanism.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2022.09a
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• pp.45-45
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• 2022

일당귀[Angelica acutiloba (Siebold & Zucc.) Kitagawa]는 산형과(Apiaceae), 당귀속(Angelica)에 속하는 다년생 식물로 일본이 원산지다. 국내에서는 참당귀(A. gigas)와 더불어 뿌리를 약용의 목적으로 재배하며, 잎과 줄기는 쌈채소로 이용하는 작물 중 하나이다. 본 연구의 목적은 일당귀에 대한 GA₃ 처리 및 온도에 따른 발아특성을 분석하여 약용 및 식용으로 활용도가 높은 일당귀의 재배 및 생산에 대한 기초자료로 사용함에 있다. 연구에 사용된 일당귀의 종자는 강원도 태백시에 위치하는 일당귀 재배농가에서 2021년 10월에 채종한 종자를 구입하여 실험에 사용하였고, 종자의 수분흡수율과 다온도 종자발아기를 활용하여 GA₃농도 4조건(50 ppm, 100 ppm, 500 ppm, 1,000 ppm), 온도 6조건(5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃, 30 ℃)에 따른 발아특성을 조사하였다. 연구결과 일당귀 종자 100립의 초기 무게 0.264 g에서 증류수 침지 2시간이 경과 후 약 60 %의 무게가 증가한 0.424 g으로 증가하였고, 이후 5 %내외의 수분흡수율을 보이며 48시간 경과 후 약 120% 증가한 0.587 g을 나타냈으며, 이후 72시간 경과 후 0.582 g으로 측정되어 일당귀 종자의 수분포화도는 약 120%정도 내외로 사료된다. GA₃농도 및 온도에 따른 발아율은 500 ppm의 GA₃농도에서 가장 높은 75.63 %의 발아율을 나타냈으며, 15 ℃와 20 ℃의 온도에서 가장 높은 77.6 %의 발아율을 나타냈다. 하지만 각각의 GA₃농도 및 온도에 따른 발아율은 500 ppm의 GA₃농도, 10 ℃의 온도 처리구에서 가장 높은 89.9 %의 발아율을 나타냈으며, 5 ℃의 온도 처리구에서는 모든 GA₃처리구에서 발아가 진행되지 않았다.

• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.125-129
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• 2021

We investigated the electronic property and atomic structure for chalcopyrite (CH) Al_xGa_1-xAs semiconductor by using first-principles FPLMTO method. The CH-Al_xGa_1-xAs exhibits a p-type semiconductor with a direct band-gap. For low Al concentration unoccupied hole-carriers are induced, but for high Al concentration it is formed a localized bonding or anti-bonding state below Fermi level. The hybridization of Al(3s)-Ga(4s, or 4p) is larger than that of Al(3s)-As(4s, or 4p). And the Al film on As-terminated surface, Al/AsGa(001), is more energetically favorable one than that on Ga-terminated (001) surface. Consequently, the band-gap of CH-Al_xGa_1-xAs system increases exponentially with increasing Al concentration. The change of lattice parameter is shown two different configurations with increasing Al concentration. The calculated lattice parameters for CH-Al_xGa_1-xAs system are compared to the experimental ones of zinc-blend GaAs and AlAs.

• Journal of Practical Agriculture & Fisheries Research
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• v.16 no.1
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• pp.55-66
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• 2014

This study has been conducted to investigate the treatment time and concentration of GA₃ solution dipping for labor saving in 'Campbell Early' grapevine. The rachis growth at harvest was reduced by GA₃ solution dipping before 5 days flowering, and increased significantly by GA₃ solution dipping treatment at full bloom and after 5 days full bloom. GA₃ 5, 10, 20 mg·L^-1 dipping treatment before 5 days flowering and GA₃ 20 mg·L^-1 treatment of full bloom and after 5 days full bloom showed a rachis twist phytotoxicity symptom. The optimum GA₃ concentrations for rachis growth promotion without phytotoxicity were 5 mg·L^-1 and 10 mg·L^-1. The degree of compact berry, bloom, skin color, SSC and acidity at harvest by GA₃ solution dipping treatment time between concentration were not different from those of control. But the fruit berry weight was decreased by before 5 days flowering treatment when compared with control. There were no differences in full bloom and after 5 days full bloom treatment. The occurrence percent of berry cracking at before 5 days flowering and after 5 days full bloom treatment were significantly increased by GA₃ treatment. The bitter rot occurrence of berry at harvest was not affected by GA₃ treatment. Total rachis length of fruit cluster was increased by full bloom and 5 days after full bloom treatment. The length of rachis increased without reference to them position at full bloom and 5 days after bloom treatment. Accordingly, GA₃ 5 mg·L^-1 solution dipping treatment at full bloom and 5 days after full bloom were can be effectively for rachis growth promotion.

• Journal of Environmental Science International
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• v.32 no.1
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• pp.77-88
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• 2023

Kadsura coccinea (Lem.) A.C. Smith is used as a medicinal plant and cosmetic material in China and Southeast Asia. To mass-produce Kadsura coccinea seedlings, the effects of gibberellic acid (GA₃) and cold stratification treatments on seed germination were investigated. Seed germination rate with GA₃ treatment was most effective at concentrations of 250 or 500 mg/L. With respect to mean germination time (MGT), mean daily germination, and T₅₀ (days to reach 50% seed germination), the germination-promoting effect was improved as the concentration of GA₃ increased. Stem growth of seedlings was the highest following GA₃ treatments of 250 and 500 mg/L, and the growth promoting effect gradually decreased as the concentration of GA₃ decreased. Root growth was stimulated at GA₃ concentrations of 250-1,000 mg/L. Examination of the effect of stratification treatment for 15, 30 and 60 days at temperatures of 0, 5 and 10℃ on the germination rate revealed that the most stratification treatment temperature was 10℃, and the results improved with longer treatment periods. Altogether, GA₃ and stratification treatments improved the seed germination rate, shortened the MGT, improved germination uniformity, and produced healthy seedlings.

• Journal of Practical Agriculture & Fisheries Research
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• v.14 no.1
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• pp.119-130
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• 2012

To increasing efficiency of the seed production through GA₃ treatment, treatment of GA₃ 20mg/ℓ at its fourteen leaf stage had an effect on 21% increasing seed yield at leaf lettuce (cv.'Ttugseomjeokchugmyeon') in seed production from 50.9ℓ/10a to 61.7ℓ/10a, and 'GA₃ 50mg/ℓ at its eight leaf and fourteen leaf stage had a effect on 14% increasing the seed yield of head lettuce (cv.'Urake') at seed production from 14.2ℓ/10a to 21.1ℓ/10a reducing rate of dead plant in field. Especially, it will be recommended for planting after June for seed production of head lettuce owing to decreasing rate of dead by soft rot and stem rot.

• Journal of Sensor Science and Technology
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• v.30 no.6
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• pp.441-445
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• 2021

The components affecting the extrinsic transconductance (g_{m_ext}) in In_0.7Ga_0.3As quantum-well (QW) high-electron-mobility transistors (HEMTs) on an InP substrate were investigated. First, comprehensive modeling, which only requires physical parameters, was used to explain both the intrinsic transconductance (g_{m_int}) and the g_{m_ext} of the devices. Two types of In_0.7Ga_0.3As QW HEMT were fabricated with gate lengths ranging from 10 ㎛ to sub-100 nm. These measured results were correlated with the modeling to describe the device behavior using analytical expressions. To study the effects of the components affecting g_{m_int}, the proposed approach was extended to projection by changing the values of physical parameters, such as series resistances (R_S and R_D), apparent mobility (𝜇_{n_app}), and saturation velocity (𝜈_sat).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.5
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• pp.504-508
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• 2022

Single crystal gallium oxide (Ga₂O₃) has been an emerging material for power semiconductor applications. However, the defect distribution of Ga₂O₃ substrates needs to be carefully characterized to improve crystal quality during crystal growth. We analyzed the type and the distribution of defects on commercial (-201) Ga₂O₃ substrates to get a basic standard prior to growing Ga₂O₃ crystals. Etch pit technique was employed to expose the type of defects on the Ga₂O₃ substrates. Synchrotron white beam X-ray topography was also utilized to observe the defect distribution by a nondestructive manner. We expect that the observation of defect distribution with three-dimensional geometry will also be useful for other crystal planes of Ga₂O₃ single crystals.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.9
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• pp.781-786
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• 2005

The binding energy in the n-type $GaAs/Al_xGa_{1-x}As$ quantum well is calculated. The shooting method, modified from the finite difference method, is used for the calculation of the subband energy level and its wave function. In order to account tot the change of the potential energy due to the charged particles, impurities and electrons, the self consistent method is employed. The wave function used for the calculation of the binding energy is assumed to be composed of the envelope function and hydrogenic 1s function. Then, the binding energies calculated by taking into account lot two different types of the hydrogenic 1s function are compared.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.34 no.1
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• pp.1-7
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• 2024

β-Ga₂O₃ is a material with a wide band gap of ~4.8 eV and a high breakdown-voltage of 8 MV/cm, and is attracting much attention in the field of power device applications. In addition, compared to representative WBG semiconductor materials such as SiC, GaN and Diamond, it has the advantage of enabling single crystal growth with high growth rate and low manufacturing cost [1-4]. In this study, we succeeded in growing a 10 mm thick β-Ga₂O₃ single crystal doped with 0.3 mol% SnO₂ through the EFG (Edge-defined Film-fed Growth) method using multi-slit structure. The growth direction and growth plane were set to [010]/(010), respectively, and the growth speed was about 12 mm/h. The grown β-Ga₂O₃ single crystal was cut into various crystal planes (010, 001, 100, ${\bar{2}}01$) and surface processed. The processed samples were compared for characteristics according to crystal plane through analysis such as XRD, UV/VIS/NIR/Spec., Mercury Probe, AFM and Etching. This research is expected to contribute to the development of power semiconductor technology in high-voltage and high-temperature applications, and selecting a substrate with better characteristics will play an important role in improving device performance and reliability.