• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.5
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• pp.169-174
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• 2022

This study is to verify the feasibility of SiC single crystal growth using recycled SiC powder. The fundamental physical properties such as particle size, shape, composition and impurities of the recycled powder were analyzed, and the sublimation behavior occurring inside the reactor were predicted using the basic data. As a result of comprehensive judgment, the physical properties of the recycled powder were suitable for single crystal growth, and single crystal growth experiments were conducted using this. 100 mm 4H-SiC single crystal ingot with a height of 25 mm was grown without polytype inclusion. In the case of micro-pipe density was 0.02 ea/cm² and resistivity characteristics was 0.015~0.020 ohm·cm², commercial level quality was obtained, but additional analysis related to dislocation density and stacking faults is required for device application.

• Clean Technology
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• v.15 no.2
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• pp.69-74
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• 2009

A high-dose ion-implanted photoresist (HDIPR) was stripped off from the surface of a semiconductor wafer by using a mixture of supercritical carbon dioxide and a co-solvent. The additional ultrasonication improved the stripping efficiency remarkably and thus reduced the stripping time by supplying physical force to the substrate. We investigated the effect of co-solvents, co-solvent concentration, and stripping temperature and pressure on the stripping efficiency. The wafer surfaces before and after stripping were analyzed by scanning electron microscopy and by an energy dispersive X-ray spectrometer. The HDIPR could be stripped off completely in 3 min with 10%(w/w) acetone/sc$C0_2$ mixture at 27.6 MPa and 343 K.

• Journal of the Korea Institute of Building Construction
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• v.23 no.1
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• pp.45-56
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• 2023

This study was conducted to examine the feasibility of preparing a durability evaluation plan in watertightness for sealant applied to a PC structure. To this end, 5 types of sealant that equally satisfy the quality standards of the relevant KS standard were selected and tested. Through this testing, it was found that 3 of the 5 types of sealant showed deterioration in watertightness and durability, such as falling off and cracking from the substrate. For the remaining two types, a visual observation showed no significant changes, but additional analysis, confirmed that there was a large difference in the stress reduction rate of the material. Therefore, based on the above results, the need for a performance review in durability between sealant was confirmed, and based on this, the validity of the durability evaluation plan that can be used in product selection was quantitatively confirmed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.34 no.2
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• pp.55-60
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• 2024

Two-dimensional (2D) RuO₂ nanosheets with nanometer thickness were synthesized using a chemical exfoliation method. The synthesized 2D-RuO₂ was hybridized with Ag-nanowire (NW), which is attracting attention as a next-generation transparent electrode material. After coating Ag-NW on the substrate, 2D-RuO₂ was subsequently coated on the Ag-NW. Although there was a decrease in optical transmittance, the hybridization of 2D-RuO₂ confirmed the effect of reducing sheet resistance. Furthermore, the flexibility of the fabricated transparent electrodes was also studied. It was confirmed by the change in sheet resistance after bending. The additional coating of 2D-RuO₂ improved the flexibility of the transparent electrodes.

• Journal of the Korea Institute of Building Construction
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• v.24 no.1
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• pp.35-42
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• 2024

This research explores the potential of methyl methacrylate(MMA) as a material for road repair applications. It specifically examines two MMA formulations, referred to as type A and type B, in relation to their performance on concrete substrates. The evaluation criteria included drying time, tensile bond strength, and resistance to alkali. The condition of the substrate surface was varied across three curing environments: constant temperature and humidity(R), immersion in water(W), and immersion in water with chloride ions(N). The findings indicate that type B MMA exhibits a quicker drying time and superior resistance to alkali compared to type A. While type A demonstrated greater tensile bond strength, it failed to maintain adhesion with the concrete base. Based on the parameters tested in this study, type B MMA emerges as the more favorable option for road repair contexts. Nonetheless, the study underscores the necessity for additional testing on asphalt substrates to fully assess the material's durability and applicability for long-term road maintenance.

• Journal of IKEEE
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• v.28 no.3
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• pp.279-284
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• 2024

In this paper, we propose a novel method for implementing a microstrip patch antenna with circular polarization characteristics through an asymmetric inset feed structure. The proposed method involves designing an antenna by taking advantage of the length difference of the asymmetric inset slots inserted into the antenna, as well as the lengths of additional slots incorporated into the design to achieve circular polarization characteristics. Using this approach, we designed and fabricated an antenna operating at 2.4 GHz in the S-band for satellite communication systems, utilizing a 1 mm thick FR-4 dielectric substrate. The measurement results confirmed a gain of 2dBi, an axial ratio of less than 3dB, and a reflection coefficient below -10dB in the frequency range of 2.35 to 2.43 GHz. Based on these results, it is expected that by employing the proposed method, circularly polarized antennas utilizing inset feeds can be realised, thereby making them applicable in small satellite communication systems and various wireless IoT environmental service applications that use the ISM band.

• Microbiology and Biotechnology Letters
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• v.17 no.2
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• pp.100-108
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• 1989

Thirty-six aromatic compound biodegraders; 10 strains for benzoate, 10 for salicylate, 6 for m-toluate, and 10 for DL-camphor were isolated and taxonomically characterized. A mutant Pseudomonas strain, Ben 6-2, derived from Ben 6 revealed remarkably improved ability to metabolize benzoate. Thus enhancement of the average substrate removal rate from 5.2 to 11.0mg/$\ell$/ hr was attained by the mutant. Both of strains Sal 7 and Tol 2, degraders of salicylate and m-toluate respectively, were classified as Pseudomonas sup. Both strains were found to be extremely effective in metabolizing each aromatic substrates. The average substrate degradation rates in minimal salt media containing 2,200mg/$\ell$ of the substrate were calculated to be 40.1 mg/$\ell$/ hr for strain Sal 7 and 33.0mg/$\ell$/ hr for Tol 2. Cam 10, a camphor degrading strain was demonstrated to be capable of mineralizing benzoate, phenol, toluene, octane, cyclohexane and xylene as well as camphor. Strain 1040 isolated from Cam 10 after repented adaptation to 1,000 mg/$\ell$ m-toluate gained the ability to utilize toluate as a sole carbon source. The mutant Brew actively at the expense of a mixture of car-bon sources; camphor, m-toluate, benzoate and phenol (each: 200 mg/$\ell$) and utilized the substances in the preferential order of camphor, phenol, benzoate, and m-toluate. Among the biodegraders examined Cam 1040 and Tol 2 were detected to harbor plasmid. The plasmid from Cam 1001 was determined to be about 98kb, and evidenced to encode the enzyme(s) for the degradation of camphor. For the further diversification of the metabolic potentials of Cam 1040, the NAH 2 plasmid of Pseudomonas putida NCIB 9816 was transferred to Cam 1040 by conjugation. The exconjugant obtained, Cam 1043, proved to gain an additional ability to metabolize salicylate and naphthalene.

• Korean Journal of Materials Research
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• v.5 no.8
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• pp.988-996
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• 1995

CuInSe$_2$this films as a light absorber layer were fabricated by vacuum evaporation using In$_2$Se$_3$and Cu$_2$Se precursors and their properties were analyzed. Indium selenide films of 0.5${\mu}{\textrm}{m}$ thickness were first deposited by vacuum evaporation of In$_2$Se$_3$ on a Corning 7059 glass substrate. The films deposited at suscepor temperature of 40$0^{\circ}C$ showed a flat surface morphology with densely Packed grain structure. CuInSe$_2$films directly formed by evaporating Cu$_2$Se on the predeposited In$_2$Se$_2$films also showed a very flat surface when the susceptor temperature was $700^{\circ}C$. Cu$_2$Se, a second phase in the CuInSe$_2$film, was removed by evaporating additional In$_2$Se$_3$on the CuInSe$_2$film at $700^{\circ}C$. The grain size of 1.2${\mu}{\textrm}{m}$ thick CuInSe$_2$, film was about 2${\mu}{\textrm}{m}$ and the film had a (112) preferred orientation. As the amount of deposited In$_2$Se$_3$increased, the electrical resistivity of CuInSe$_2$films increased because of the decrease of hole concentration. But the optical band gap was almost constant at the value of 1.04eV, The CuInSe$_2$film grown on a Mo/glass substrate had a similar smooth microstructure compared to that on a glass substrate. A solar cell with ZnO/CdS/CuInSe$_2$/Mo structure may be realized based on the above CuInSe$_2$films.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.114-114
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• 2009

ZnO has received considerable attention due to its potential applicability to optoelectronic devices such as ultraviolet-light emitting diodes (UVLEDs) and laser diodes (LDs). As well known, however, polar ZnO with the growth direction along the c-axis has spontaneous and piezoelectric polarizations that will result in decreased quantum efficiency. Recently, nonpolar ZnO has been studied to avoid such a polarization effect. In order to realize applications of nonpoar ZnO-based films to LEDs, growth of high quality alloys for quantum well structures is one of the important tasks that should be solved. $Mg_xZn_{1-x}O$ and $Cd_xZn_{1-x}O$ is ones of most promising alloys for this application because the alloys of ZnO with MgO and CdO provide a wide range of band-gap engineering spanning from 2.4 to 7.8 eV. In this study, we investigated on $Mg_xZn_{1-x}O$ films grown with various Mg/Zn flux ratios The films were grown on R-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PAMBE). we investigated on $Mg_xZn_{1-x}O$ films grown with various Mg/Zn flux ratios. The films were grown on R-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PAMBE). With the relatively low Mg/Zn flux ratios, a typical striated anisotropic surface morphology which was generally observed from the nonpolar (11-20) ZnO film on r-plane sapphire substrates. By increasing the Mg/Zn flux ratio, however, additional islands were appeared on the surface and finally the surface morphology was entirely changed, which was generally observed for the (0001) polar ZnO films by losing the striated morphology. Investigations by X-ray $\Theta-2{\Theta}$ diffraction revealed that (0002) and (10-11) ZnO planes are appeared in $Mg_xZn_{1-x}O$ films by increasing the Mg/Zn flux ratio. Further detailed investigation by transmission electron microscopy (TEM) and photoluminescence (PL) will be discussed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.6
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• pp.706-713
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• 2010

In this paper, the small loop antenna with a parasitic loop structure for penta-band mobile phone application is proposed. This antenna is composed of a feed monopole, a radiating loop antenna with a parasitic loop structure and an additional radiating element. The antenna is printed on the very thin flexible substrate to mount on the dielectric carrier with a volume of 40 mm$\times$11 mm$\times$3 mm. The bandwidth of the proposed antenna is 402 MHz(773~1,175 MHz) for low band and 583 MHz(1,622~2,205 MHz) for high band. As a result, the proposed antenna covers the five bands of GSM850, GSM900, DCS1800, PCS1,900 and WCDMA for a 3:1 VSWR. Moreover, the radiation pattern, gain and efficiency are appropriate for mobile handset. Therefore, this antenna is suitable for small sized multi-band mobile handset applications.