• Journal of the Korean Vacuum Society
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• v.18 no.6
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• pp.474-480
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• 2009

We have investigated optical properties of InAs quantum dots (QDs) grown on GaAs (100) substrate by molecular beam epitaxy, by means of photoluminescence (PL) and time-resolved PL spectroscopy. InAs QDs were grown by using In interruption growth technique, in which the In flux was periodically interrupted by a closed In shutter during InAs QDs growth. The shutter of In source was opened for 1 s and then closed for 0, 9, 19, 29, or 39 s. This growth sequence was repeated 30 times during QDs growth. For each sample, the total amount of In contributing to the growth was the same (30 s) but total growth time was varied during the InAs growth. As the In interruption time is increased from 0 to 19 s, the PL peak position of the QDs is red-shifted from 1096 to 1198 nm, and the PL intensity is increased. However, the PL peak is unchanged and the intensity is decreased as the In interruption time is increased further to 39 s. The PL decay times measured at the PL peak position for all the InAs QDs are independent on the QD growth conditions and showed about 1 ns. The red-shift of PL peak and the increase of PL intensity can be explained due to increased QD size and the enhancement in the migration of In atoms using In interruption technique. These results indicated that the size and shape of InAs QDs can be controlled by using In interruption growth technique. Thus the emission wavelength of the InAs QDs on GaAs substrate can also be controlled.

• Journal of the Korean Vacuum Society
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• v.19 no.5
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• pp.365-370
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• 2010

The growth interruption effects on growth mode of the GaAs and AlGaAs epitaxial layers grown on GaAs substrate by molecular beam epitaxy were investigated. Growth process of the epitaxial layers as a function of the growth interruption time was observed by reflection high energy electron diffraction (RHEED). The growth interruption time was 0, 15, 30, 60 s. The GaAs/$Al_{0.3}Ga_{0.7}As$ multi quantum wells (MQWs) with different growth interruption time were grown and its properties were investigated. RHEED intensity oscillation and optical property of the MQWs were dependent on the growth interruption time. When the growth interruption time was 30 s, interface between the well and barrier layers became sharper.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.636-639
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• 2001

InGaN/GaN multiple quantum wells (MQWs) grown with various growth interruptions between the InGaN well and GaN barrier by metal-organic chemical vapor deposition were investigated using photoluminescence, high-resolution transmission electron microscopy, and energy filtered transmission electron microscopy (EFTEM). The luminescence intensity of the MQWs with growth interruptions is abruptly reduced compared to that of the MQW without growth interruption. Also, as the interruption time increases the peak emission shows a continuous blue shift. Evidence of indium clustering is directly observed both by using an indium ratio map of the MQWs and from indium composition measurements along an InGaN well using EFTEM. The higher intensity and lower energy emission of light from the MQW grown without interruption showing indium clustering is believed to be caused by the recombination of excitons localized in indium clustering regions and the increased indium composition in these recombination centers.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.4
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• pp.45-52
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• 2007

Electric power is an important element in any modern economy. The availability of a reliable power supply at a reasonable cost is important for the economic growth and development of a country. Electric power utilities throughout the world therefore strive to meet customer demands economically with high quality and reliability. As the power industry moves towards open competition, therefore, there has been a call for a methodology by which to evaluate power system reliability through the use of customer interruption characteristics. This paper presents the results of an investigation and analysis of interruption characteristics of an industrial customer in Korea. This study used a direct visit survey to determine the investigation and analysis of electric service quality and the characteristics of industrial customers in Korea. A customer survey conducted throughout Korea via personal interviews of 660 sample customers is presented here. Variation according to characteristics of interruption such as duration, time of day, frequency and day of interruption was also investigated

• Journal of Bio-Environment Control
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• v.31 no.4
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• pp.319-324
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• 2022

The objective of this study was to determine the proper night interruption of photoperiods and dark periods for accumulating bioactive compounds of Agastache rugosa without decreasing plant growth. Five-week-old seedlings were transplanted in a DFT system with white LEDs. A. rugosa was treated with night interruption time treatments of 18:1:2:3, 18:2:2:2, 18:3:2:1 (light:dark:light:dark), and 20:4 (control) for 4 weeks. There were no significant differences except for leaf length, leaf width, and the number of flowers. The content of antioxidants in the shoot of A. rugosa was high in tilianin and acacetin, and the content of rosmarinic acid (RA) was significantly higher in the underground part. The RA content per dry weight of A. rugosa was 47.92 and 51.46% higher than that of the control in 18:1:2:3 and 18:2:2:2, and tilianin and acactin per dry weight were significantly higher in 18:3:2:1. There was no significant difference in growth due to the same day light integral, but 18:2:2:2 showed high total polyphenol contents. Therefore, it is thought that the effect of increasing secondary metabolites of A. rugosa without degradation of growth can be expected through night interruption treatment in plant factory cultivation systems using artificial light.

• Asian Journal of Turfgrass Science
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• v.23 no.1
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• pp.35-44
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• 2009

This study was carried out to examine the growth performance of 4 species of cool-season grasses and 4 species of zoysiagrasses under salt injury in Seo-san reclaimed area. Grasses were grown on the plots with capillary water interruption layer (WCWIL) and without capillary water interruption layer (WOCWIL) soil systems. Cool-season grass and seeding-type zoysiagrass plots were seeded on 6 Jun, 2006. Vegetative zoysiagrass 'Junggi' was established by sprigging and 'Senock' and 'Millock' were plugged. Electric conductivities of irrigation water (ECw) ranged from 0.28 to $3.3\;dS{\cdot}m^{-1}$. Electric conductivities (ECe) of the soil with capillary water interruption layer and without capillary water interruption layer ranged from 0.55 to $9.4\;dS{\cdot}m^{-1}$ and from 1.84 to $9.4\;dS{\cdot}m^{-1}$ respectively. Leaf color, turf quality, coverage rates, and growth rates were rated visually for 2 years. Zoysiagrass 'Junggi', creeping bentgrass, zoysiagrass 'Senock' and 'Millock' showed acceptable growth at salty fairway condition, while Kentucky bluegrass, perennial ryegrass, Kentucky bluegrass mixed with perennial ryegrass, and seeded zoysiagrass 'Zenith' showed establishment rates below 70%. These results will be useful when choosing turf grass species and cultivars for the golf courses in reclaimed land area.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.5
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• pp.543-547
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• 1995

This study was conducted to light intensity and night interruption on leaf production in perilla. Using two cultivars ; og-dong and Yeup-sil. The present studies were conducted to investigate effect of the light intensity and night interruption for prolongation of vegetative growth by flowering inhibition in the National Honam Crop Experiment Station, R. D. A, Iri, Korea. The results are summarized as followes, varietal differences of days to flower initiation were not significant by the light intensity and night interruption, however differences of days to flower initiation light intensity or night interruption treatment were higly significant. Flowering of perilla was prolongated in high light intensity and in long night interruption. Between the factors treated flowering of perilla was more influenced by light intensity than night interruption. Days to flower initiation of perilla were light intensity(0.5∼1 Lux) in 30 mins night interruption, however 3∼10 light intensity in 60 mins night interruption and 30∼100 Lux light intensity in 10, 30, 60 mins night interruption treatment were not flowering. Plant height, leaf area and dry weight of perilla were the highest in 30∼100 Lux light intensity treatment than in the other treatments. The results would be avaliable establish year-round production methods for low cost of perilla leaf.

• Journal of the Korean Vacuum Society
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• v.12 no.S1
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• pp.95-99
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• 2003

We successfully grew InN/GaN single quantum well structures by metal-organic chemical vapor deposition and confirmed their formation by optical and structural measurements. We speculate that relatively high growth temperature ($730^{\circ}C$) of InN layer enhanced the formation of 2-dimensional quantum well structures, presumably due to high adatom mobility. As the growth interruption time increased, the PL emission efficiency from InN layer improved with peak position blue-shifted and the dislocation density decreased by one order of magnitude. The high resolution cross-sectional TEM images clearly showed that the InN layer thickness reduced from 2.5 nm (without GI) to about I urn (with 10 sec GI) and the InN/GaN interface became very flat with 10 sec GI. We suggest that decomposition and mass transport processes on InN during GI is responsible for these phenomena.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.146-147
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• 2012

InP 기판위에 자발성장법으로 성장된 InAs 양자점은 $1.55{\mu}m$ 영역에서 발진하는 양자점 반도체 레이저 다이오드 및 광 증폭기를 제작할 수 있기 때문에 많은 관심을 받고 있다. 광통신 대역의 $1.55{\mu}m$ 반도체 레이저 다이오드 및 광 증폭기 분야에서 InAs/InP 양자점이 많은 관심을 받고 있으나, InAs/GaAs 양자점에 비해 제작이 어려운 단점을 가지고 있다. InAs/InP 양자점은 InAs/GaAs 양자점에 비해 격자 불일치가 작아 양자점의 크기가 크고 특히 As 계 박막과 P 계박막의 계면에서 V 족 원소 교환 반응으로 계면 특성 저하가 발생하여 성장이 까다롭다. As 과 P 간의 교환반응은 성장온도와 V/III 에 의해 크게 영향을 받는 것으로 보고되었다. 그러나, P계 InGaAsP 박막 위에 InAs 성장 시 발생하는 As/P 교환반응에 대한 연구는 매우 적다. 본 연구에서는 InGaAsP 박막 위에 InAs 양자점 성장 시 GI (growth interruption)에 의한 As/P 교환반응이 InAs 양자점의 형상 및 광학적 특성에 미치는 영향을 연구하였다. 시료는 수직형 저압 Metal Organic Chemical Vapor Deposition (MOCVD)를 이용하여 $520^{\circ}C$의 온도에서 성장하였다. 그림1(a) 구조의 양자점은 InP (100) 기판위에 InP buffer layer를 성장한 후 InP와 격자상수가 일치하는 $1.1{\mu}m$ 파장의 InGaAsP barrier를 50 nm 성장하였다. 그 후 As 분위기 하에서 다양한 GI 시간을 주었고 그 위에 InAs 양자점을 성장하였다. 양자점 성장 후 InGaAsP barrier를 50 nm, InP capping layer를 50 nm 성장하였다. AFM측정을 위해 InP capping layer 위에 동일한 GI 조건의 InAs/InGaAsP 양자점을 성장하였고 양자점 성장 후 As분위기 하에 온도를 내려주었다. 그림1(b) 구조의 양자점은 그림1(a) 와 모든 조건은 동일하나 InAs 양자점과 InGaAsP barrier 사이에 GaAs 2ML를 삽입한 구조이다. 양자점 형상 특성 평가는 Atomic force microscopy를 이용하였으며, 광특성 분석은 Photoluminescence를 이용하였다.

• Journal of the Korean Vacuum Society
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• v.7 no.2
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• pp.104-111
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• 1998

The InGaAs/InP quantum wells(QWs) were grown by low pressure metalorganic chemical vapor deposition and the effects of growth interruption steps on their interfacial structures were investigated by measuring photoluminescence spectra. When InP or InGaAs surface was treated under the same group V ambient, the full width at half maximum (FWHM) of the QW peak increased possibly due to the incorporation of impurities during the growth interruption time. When InP surface was treated under $AsH_3$, howerer, the PL peak showed red-shift due to the As-P exchange reaction and the change of FWHM was not remarkable. The effective thickness of InAs interfacial layer formed during $AsH_3$, treatment on the InP surface was calculated to be 1~2 monolayers. In the case of InGaAs treatment under $PH_3$, the PL peak energy and the FWHM increasied. This results suggest that $PH_3$ treatment on the InGaAs surface suppresses the incorporation of As into the subsequent InP layer and the local replacement of As by P occurs simultaneously.