• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.211.2-211.2
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• 2016

그래핀은 본연의 우수한 물성으로 인하여 전자소자, 에너지 저장매체, 유연성 전도막 등 다양한 분야로의 응용가능성이 제기되었으나, 실제적인 응용을 위해서는 구조적인 결함을 최소화하며, 특성을 자유로이 제어하거나 향상시키는 공정의 개발이 요구된다. 특히 그래핀을 전자소자로 응용하기 위해서는 전기적 특성을 제어하는 것이 요구된다. 일반적으로 화학적 도핑은 그래핀의 전기적 특성을 제어하는 효율적인 방법으로 알려져 있다. 화학적 도핑은 그래핀을 구성하는 탄소원자를 이종원자로 치환하거나 표면에 흡착시켜 기능화 된 그래핀을 얻는 방법으로, 특정 가스 분위기에서 고온 열처리하거나 활성종들이 존재하는 플라즈마에 노출시키는 방법이 제시되었다. 특히 플라즈마를 이용한 도핑방법은 저온에서 단시간의 처리로 도핑이 가능하고, 플라즈마 변수를 변경하여 도핑정도를 수월하게 제어할 수 있다는 장점을 가지고 있다. 그러나 플라즈마내의 극성을 띄는 다양한 활성종들의 충돌효과로 인하여 구조적인 손상이 발생하여 오히려 특성이 저하될 수 있어 이를 고려한 플라즈마 공정조건의 설정이 필수적이다. 따라서 본 연구에서는 플라즈마에 노출된 그래핀의 Raman 특성을 고찰함으로써 화학적 도핑과 구조적인 결함의 경계를 확립하고 구조결함의 형성을 최소화한 효율적인 도핑조건을 도출하였다. 그래핀은 물리적 박리법을 이용하여 300 nm 두께의 실리콘 산화막이 존재하는 실리콘 웨이퍼 위에 제작하였으며, 평행 평판형 직류 플라즈마 장치를 이용하여 전극의 위치, 인가전력, 처리시간을 변수로 암모니아($NH_3$) 플라즈마를 방전하여 그래핀의 Raman 특성변화를 관찰하였다. 그래핀의 구조적 결함 및 도핑 효과는 라만 스펙트럼의 D, D', 2D밴드의 강도와 G밴드의 위치와 반치폭(Full width at half maximum; FWHM)의 변화를 통해 확인하였다. 그 결과, 인가전력과 처리시간에 따라 결함형성과 질소도핑 영역이 구분 가능함을 확인하였으며, 이를 바탕으로 결함형성을 최소화한 효율적인 도핑조건이 접지전위, 0.45 W의 인가전력, 처리시간 10초이며, 최적조건에서 계산된 도핑레벨은 $1.8{\times}10^{12}cm^{-2}$임을 확인하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.6
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• pp.95-99
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• 2013

Furnace is currently the most important doping process using POCl3 in solar cell. However furnace need an expensive equipment cost and it has to purge a poisonous gas. Moreover, furnace typically difficult appling for selective emitters. In this study, we developed a new atmospheric pressure plasma source, in this procedure, we research the atmospheric pressure plasma doping that dopant is phosphoric acid($H_3PO_4$). Metal tube injected Ar gas was inputted 5 kV of a low frequency(scores of kHz) induced inverter, so plasma discharged at metal tube. We used the P type silicon wafer of solar cell. We regulated phosphoric acid($H_3PO_4$) concentration on 10% and plasma treatment time is 90 s, 150 s, we experiment that plasma current is 70 mA. We check the doping depth that 287 nm at 90 s and 621 nm at 150 s. We analysis and measurement the doping profile by using SIMS(Secondary Ion Mass Spectroscopy). We calculate and grasp the sheet resistance using conventional sheet resistance formula, so there are 240 Ohm/sq at 90 s and 212 Ohm/sq at 150 s. We analysis oxygen and nitrogen profile of concentration compared with furnace to check the doped defect of atmosphere.

• Magazine of the Korean Society of Agricultural Engineers
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• v.28 no.3
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• pp.99-106
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• 1986

This study was carried out to investigate the effects of moisture content, temperature, C/N ratio and pH of the sewage sludge mixed with hulle and sawdusts for making compost under aerobic condition and to improve the defect of the structure of experimental equipment heat lose and handling method. and obtained results were as follows 1.The temperature was reached 73$^{\circ}$ C around 50 hours fermentation in the condition of 0.8 L/min. of air and 60.4% of moisture content. and favorable moisture content of initial condition ranged from 50 to 65% 2.The temperature near bottom of the batch composter was decreased due to evaporate water vapor and lose the heat produced during aeration. and it is required to be improved. 3.The temperature in the batch composter from the center to the inside wall surface was gradually decreased. the temperatures of the points located in r=9cm and the wall surface were 4$^{\circ}$ C and 6$^{\circ}$ C respectively. and therefore it is required to be insulated. 4. The maximum C02 production was obtained as 7.3% per volume in the temperature of 63$^{\circ}$C at the moisture content of 60% 5.The temperature range of active microbes growth was found to be as 20$^{\circ}$C to 40$^{\circ}$C in the case of mesophiles and 50$^{\circ}$C to 65$^{\circ}$C in the case of thermophiles due to increase and decrease C02 production. 6.C/N ratio after decomposition was 1.3 to 2.6 smaller than that of initial one due to increase the amount of nitrogen. The more C/N ratio increased. the less the reaction velocity decresed. The optimum of it as found to be 30. 7.pH values after decomposition were slightly increased than that of initial ones. The reaction velocity was decreased at acid and alkall condition. Therefore it is neseseary to neutralize the medium to improve the reaction.

• Journal of Environmental Science International
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• v.21 no.11
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• pp.1307-1320
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• 2012

The purpose of this paper is to provide information on planting construction for healthy plant growth. To achieve this purpose, this study analyzed the planting type, planting density, withering rate, soil characteristics, and cambium electrical resistance (CER) of withered trees in an apartment complex with a high withering rate. The major plant groups examined consisted of native broad-leaved tree species (39.3%), native narrow-leaved tree species (24.2%), and native broad-leaved - exotic narrow-leaved tree species (16.4%). The planting density of the green area, where trees were planted from 0.0 to 0.3 trees per unit area, was measured as 98.4%. Withered trees were found in 19 of the 20 planted species, and the withering rate was 41.8% (610 withered/1,461 planted). Withering rates for tree species were measured as follows: Sophora japonica and Salix babylonica (100.0%), Magmolia denudata (84.3%), Lindera obtusiloba (74.7%), cornus kousa (69.3%), acer triflorum (69.2%), diospyros kaki (66.7%), Prunus yedoensis (62.8%), Acer palmatum (52.6%), Prunus armeniaca (51.1%), Chaenomeles sinensis (43.7%), Ginkgo biloba (40.9%), Zelkova serrata (31.0%), Cornus officinalis (28.6%), Taxus cuspidata (25.6%), Pinus densiflora (21.4%), Pinus parviflora (15.2%), Pinus strobus (14.6%), and Abies holophylla (10.3%). Soil chemical analyses for 18 samples revealed that as the withering rate increased, the following occurred: (a) the ratio of silt and clay in soil increased; (b) the soil pH, organic matter rate, nitrogen, available phosphorus, and cation exchange capacity (CEC) in samples were graded as "inadequate," based on the plant grading evaluation; and (c) the NaCl and cation exchange capacity were evaluated as "somewhat satisfactory." The measurement of CER for withering rate shows electrical resistance for higher withering rate are higher, which could predict that a tree will not grow well.

• Journal of Welding and Joining
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• v.28 no.1
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• pp.66-71
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• 2010

With large specific strength and outstanding corrosion resistance and erosion resistance in sea water, titanium and titanium alloy are widely used in heat exchanger production. In particular, pure titanium demonstrates outstanding molding performance and may be considered optimal for production of heat exchanger. Since titanium is very vulnerable to oxidation and embrittlement during welding, processes with less heat input are widely used, and laser welding is widely applied by considering production performance and shield etc in atmosphere. So far, 1st report and 2nd report compared and analyzed embrittlement degrees by bead colors of weldment through oxygen and nitrogen quantitative analysis and hardness measurement, and evaluated welding performance and mechanical properties of butt welding. This study evaluated field applicability of lap welding to heat exchange plate of LPG re-liquefaction device for ships through tensile stress test, hardness test and internal pressure test etc after deducing optimal weding condition and applying to actual heat exchange plate. In bead overlap area, the experiment produced sound welds with no porosity or defect by increasing and decreasing laser power, and tensile-shear test results indicated virtually the same tension and yield strength as base metal. As a result of measuring hardness at lateral cross section and bead overlap zone of actual heat exchanger welds, hardness difference within 20Hv was produced at base metal, HAZ and weldment, and as a result of pneumatic and hydraulic pressure test, no leakage occurred.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1267-1267
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• 2001

The existing fruit sorter has the method of tilting tray and extracting fruits by the action of solenoid or springs. In peaches, the most sort processing is supported by man because the sorter make fatal damage to peaches. In order to sustain commodity and quality of peach non-destructive, non-contact and real time based sorter was needed. This study was performed to develop peach sorter using near-infrared spectroscopy in real time and nondestructively. The prototype was developed to decrease internal and external damage of peach caused by the sorter, which had a way of extracting tray with it. To decrease positioning error of measuring sugar contents in peaches, fiber optic with two direction diverged was developed and attached to the prototype. The program for sorting and operating the prototype was developed using visual basic 6.0 language to measure several quality index such as chlorophyll, some defect, sugar contents. The all sorting result was saved to return farmers for being index of good quality production. Using the prototype, program and MLR(multiple linear regression) model, it was possible to estimate sugar content of peaches with the determination coefficient of 0.71 and SEC of 0.42bx using 16 wavelengths. The developed MLR model had determination coefficient of 0.69, and SEP of 0.49bx, it was better result than single point measurement of 1999's. The peach sweetness grading system based on NIR reflectance method, which consists of photodiode-array sensor, quartz-halogen lamp and fiber optic diverged two bundles for transmitting the light and detecting the reflected light, was developed and evaluated. It was possible to predict the soluble solid contents of peaches in real time and nondestructively using the system which had the accuracy of 91 percentage and the capacity of 7,200 peaches per an hour for grading 2 classes by sugar contents. Draining is one of important factors for production peaches having good qualities. The reason why one farm's product belows others could be estimated for bad draining, over-much nitrogen fertilizer, soil characteristics, etc. After this, the report saved by the peach grading system will have to be good materials to farmers for production high quality peaches. They could share the result or compare with others and diagnose their cultural practice.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.41 no.5
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• pp.619-624
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• 1996

An experiment was carried out to find out the effects of water foxtail on weed control and rice yield as well as on the reduction of nitrogen application in no tillage transplanted paddy field. Paddy field was dominated by water foxtail whose soil covering degree was adjusted from 8 to 6 by treatment of paraquat (70 l /10a of solution diluted by 1, 000 times). Thirty five-day old seedling was mechanically transplanted and reduced nitrogen, 80% of conventional application was applied at the paddy field. The higher failure in seedling stand was observed at higher degree of soil covering by water foxtail. The failure of seedling stand with covering degree of 8(no paraquat) was 37.4%, while that of covering degree of 6(paraquat-treated) was 12.3%. However, the seedling stand failure was completely recovered at covering degree of six at two weeks after transplanting. The mechanical transplanting made water foxtail in the paddy field fall on the ground whose panicle part was recovered from falling sometimes after transplanting and whole plant died with slow scenesence untill the late of June. But the water foxtail affected by paraquat produced the new panicle from uppernode of stem with dead leaves at early of June and it become die slowly untill the early of July. Though several rice field weeds were observed in the order of Echinochloa crusgallis, Cyperus serotinus, Lemma paucicostata during the active tillering stage of rice, the value of weed control due to the dominance of water foxtail was 77~78%. The death and subsequent decay of water foxtail during the active tillering stage of rice induced the soil reduction which again defect the growth of rice root. The more vigerous rice growth was observed in the plot dominated with water foxtails, than control plot. The yields of rice in the water foxtail (degree 6) plot was 629kg per l0a as brown rice, the same as that of control plot. In conclusion, the no-tillage transplanting with control of covering degree of water foxtail (to degree 6) was effective in reduction of input cost such as herbicide and nitrogen fertilizer, as well as weed control without reduction of rice yield.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.5
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• pp.196-201
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• 2014

We investigated defects and surface polarity in AlN and GaN by using wet chemical etching. Therefore, the effectiveness and reliability of estimating the single crystals by defect selective etching in NaOH/KOH eutectic alloy have been successfully demonstrated. High-quality AlN and GaN single crystals were etched in molten NaOH/KOH eutectic alloy. The etching characteristics and surface morphologies were carried out by scanning electron microscope (SEM) and atomic force microscope (AFM). The etch rates of AlN and GaN surface were calculated by etching depth as a function of etching time. As a result, two-types of etch pits with different sizes were revealed on AlN and GaN surface, respectively. Etching produced hexagonal pits on the metal-face (Al, Ga) (0001) plane, while hexagonal hillocks formed on the N-face. On etching rate calibration, it was found that N-face had approximately 109 and 15 times higher etch rate than the metal-face of AlN and GaN, respectively. The size of etch pits increased with an increase of the etching time and they tend to merge together with a neighbouring etch pits. Also, the chemical mechanism of each etching process was discussed. It was found that hydroxide ion ($OH^-$) and the dangling bond of nitrogen play an important role in the selective etching of the metal-face and N-face.

• Journal of the Korean Vacuum Society
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• v.22 no.6
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• pp.321-326
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• 2013

The effect of rapid thermal annealing (RTA) on the optical properties of digital-alloy InGaAlAs multiple quantum well (MQW) structures have been investigated by using photoluminescence (PL) and time-resolved PL measurements as a function of RTA temperature. The MQW samples were annealed from $700^{\circ}C$ to $850^{\circ}C$ for 30 s in a nitrogen atmosphere. The MQW sample annealed at $750^{\circ}C$ exhibited the strongest PL intensity and the narrowest FWHM (Full width at half maximum), indicating the reduced nonradiative recombination centers and the improved interfaces between the wells and barriers. The MQW samples annealed at $800^{\circ}C$ and $850^{\circ}C$ showed the decreased PL intensities and blueshifted PL peaks compared to $750^{\circ}C$-annealed sample. The blueshift of PL peak with increasing RTA temperatures are ascribed to the increase of aluminum due to intermixing of gallium (Ga) and aluminum (Al) in the interfaces of InGaAs/InAlAs short-period superlattices. The decrease of PL intensity after annealing at $800^{\circ}C$ and $850^{\circ}C$ are attributed to the interface roughening and lateral composition modulation caused by the interdiffusion of Ga and Al and indium segregation, respectively. With increasing RTA temperature the PL decay becomes slower, indicating the decrease of nonradiative defect centers. The optical properties of digital-alloy InGaAlAs MQW structures can be improved significantly with optimum RTA conditions.

• Korean Journal of Microbiology
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• v.47 no.2
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• pp.110-116
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• 2011

In the previous study with the Saccharomyces cerevisiae S288c strains, no known function of the dual specificity kinase, ScKns1, was reported because its gene deletion did not show any noticeable phenotypic changes. Recent study with fission yeast, however, revealed the involvement of the LAMMER kinase in flocculation, filamentous growth, oxidative stress, and so on. Therefore we made Sckns1-deletion mutants with the ${\Sigma}1278b$-background, with which one can induce filamentous and adhesive growth in contrast to those of the S288c-background. The $Sckns1{\Delta}$ strains of both haploid and diploid showed defect in filamentous growth under conditions for inducing the filamentous growth such as nitrogen starvation and butanol treatment. Both kinds of the deletion mutants also showed decrease in adhesive growth on agar surface. Interestingly enough the defects of the $Sckns1{\Delta}$ strains were suppressed by the over-expression of each gene for the components of the MAPK signaling pathway such as STE11, STE12, and TEC1, respectively, but not by the upstream components, RAS2 and STE20, respectively. Although further investigations are required, these results indicate that the ScKns1 may act in place between the Ste20 and the Ste11 of the S. cerevisiae MAPK cascade.