• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.265-265
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• 2011

자발형성법으로 InP (001) 기판에 성장한 InAs/InAlGaAs 양자점(QDs: quantum dots)의 광학적 특성을 PL (photoluminescence)와 TRPL (time-resolved PL)을 이용하여 분석하였다. InAs QDs 시료는 single layer InAs QDs (QD1)과 7-stacked InAs QDs (QD2)를 사용하였다. 두 시료 모두 저온 (10 K)에서 1,320 nm에서 PL 피크가 나타나고, 온도가 증가함에 따라 PL 피크는 적색편이 (red-shift)를 보였다. 양자점의 온도를 10 K에서 300 K까지 증가하였을 때 QD1은 178 nm 적색편이 하였으며, PL 스펙트럼 폭은 온도가 증가함에 따라 증가하였다. 그러나 QD2는 264 nm 적색편이를 보였으며 PL 스펙트럼의 폭은 QD1 시료와 반대로 온도가 증가함에 따라 감소하였다. QD2의 아주 넓은 PL 스펙트럼 폭과 매우 큰 적색편이는 InAs 양자점 크기의 변화가 QD1에 비해 훨씬 크기 때문이다. QD2의 경우 InAs 층수(layer number)가 증가함에 따라 InAs QD의 크기가 점차 증가하므로 QD 크기의 변화가 single layer인 QD1 시료보다 훨씬 크다. QD1의 PL 소멸은 파장이 증가함에 따라 점차 느려지다가 PL 피크 근처에서 가장 느린 소멸 곡선을 보이고, 파장이 더 증가하였을 때 PL 소멸은 점차 빠르게 소멸하였다. 그러나 QD2의 PL 소멸곡선은 파장이 증가함에 따라 점차 빠르게 소멸하였다. 이것은 QD2는 양자점 크기의 변화가 매우 크기 때문에 (lateral size=18~29 nm, height=2.8~5.9 nm) 방출파장이 증가함에 따라 양자점 사이의 파동함수의 겹침이 증가하여 캐리어의 이완이 증가하기 때문으로 설명된다. 온도에 따른 TRPL 결과는 두 시료 모두 10 K에서 150 K 까지는 소멸시간이 증가하였고, 150 K 이후부터는 소멸시간이 감소하였다. 온도가 증가함에 따라 소멸시간이 증가하는 것은 양자점에서 장벽과 WL (wetting layer)로 운반자(carrier)의 이동, 양자점들 사이에 열에 의해 유도된 운반자의 재분배 등으로 인한 발광 재결합으로 설명할 수 있다. 150 K 이상에서 소멸시간이 감소하는 것은 열적효과에 의한 비발광 재결합 과정에 의한 운반자의 소멸이 증가하기 때문이다. 온도에 따른 TRPL 결과는 두 시료 모두 150 K까지는 발광재결합이 우세하고, 150 K 이상에서 비발광재겹합이 우세하게 나타났다.

• Korean Journal of Materials Research
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• v.29 no.9
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• pp.542-546
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• 2019

We investigate the characteristics of self-assembled quantum dot infrared photodetectors(QDIPs) based on doping level. Two kinds of QDIP samples are prepared using molecular beam epitaxy : $n^+-i(QD)-n^+$ QDIP with undoped quantum dot(QD) active region and $n^+-n^-(QD)-n^+$ QDIP containing Si direct doped QDs. InAs QDIPs were grown on semi-insulating GaAs (100) wafers by molecular-beam epitaxy. Both top and bottom contact GaAs layer are Si doped at $2{\times}10^{18}/cm^3$. The QD layers are grown by two-monolayer of InAs deposition and capped by InGaAs layer. For the $n^+-n^-(QD)-n^+$ structure, Si dopant is directly doped in InAs QD at $2{\times}10^{17}/cm^3$. Undoped and doped QDIPs show a photoresponse peak at about $8.3{\mu}m$, ranging from $6{\sim}10{\mu}m$ at 10 K. The intensity of the doped QDIP photoresponse is higher than that of the undoped QDIP on same temperature. Undoped QDIP yields a photoresponse of up to 50 K, whereas doped QDIP has a response of up to 30 K only. This result suggests that the doping level of QDs should be appropriately determined by compromising between photoresponsivity and operating temperature.

• BioChip Journal
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• v.12 no.4
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• pp.340-347
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• 2018

$F{\ddot{o}}rster$ resonance energy transfer (FRET) is extremely sensitive to the separation distance between the donor and the acceptor which is ideal for probing such biological phenomena. Also, FRET-based probes have been developing for detecting an unamplified, low-abundance of target DNA. Here we describe the development of FRET based DNA sensor based on an accumulated QD system for detecting KRAS G12D mutation which is the most common mutation in cancer. The accumulated QD system consists of the polystyrene beads which surface is modified with carboxyl modified QDs. The QDs are sandwich-hybridized with DNA of a capture probe, a reporter probe with Texas-red, and a target DNA by EDC-NHS coupling. Because the carboxyl modified QDs are located closely to each other in the accumulated QDs, these neighboring QDs are enough to transfer the energy to the acceptor dyes. Therefore the FRET factor in the bead system is enhancing by the additional increase of 29.2% as compared to that in a single QD system. These results suggest that the accumulated nanobead probe with conjugated QDs can be used as ultrasensitive DNA nanosensors detecting the mutation in the various cancers.

• Asian Journal of Business Environment
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• v.8 no.1
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• pp.23-29
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• 2018

Purpose - The purpose of this research is to make a comparative assessment of People Credit Funds (PCFs) ranking in Vietnam between the Circular No. 42/2016/TT-NHNN dated December 20, 2016 with the Decision No. 14/2007/QD-NHNN dated 09/4/2007 issued by the Governor of the State Bank. Research design, data, and methodology - This study is mainly based on the Circular No. 42/2016/TT-NHNN dated December 20, 2016 and the Decision No. 14/2007/QD-NHNN dated 09/4/2007 issued by the Governor of the State Bank on PCFs ranking. Results - The study paper has shown positive changes in PCFs ranking in Vietnam in accordance with the Circular No. 42/2016/TT-NHNN, such as increasing Capital Adequacy Ratio (CAR), maintaining CAR, improving assets quality, developing indicators of governance, management and control capability. These changes have implications for the development and efficient performance of PCFs in Vietnam. Conclusions - The classification and evaluation of PCFs will contribute to its healthy development. These finding support PCFs to understand more about rating methodology, significance of rating system and the importance of improving their rating. PCFs in Vietnam desire to develop their business effectively, they need to understand exactly and comply fully with regulations related to their field of operations.

• Toxicological Research
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• v.29 no.1
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• pp.35-42
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• 2013

Quantum dots (QDs) have received considerable attention due to their potential role in photosensitization during photodynamic therapy. Although QDS are attractive nanomaterials due to their novel and unique physicochemical properties, concerns about their toxicity remain. We suggest a combination strategy, CdSe/ZnS QDs together with curcumin, a natural yellow pigment from turmeric, to reduce QD-induced cytotoxicity. The aim of this study was to explore a potentially effective cancer treatment: co-exposure of HL-60 cells and human normal lymphocytes to CdSe/ZnS QDs and curcumin. Cell viability, apoptosis, reactive oxygen species (ROS) generation, and DNA damage induced by QDs and/or curcumin with or without ultraviolet A (UVA) irradiation were evaluated in both HL-60 cells and normal lymphocytes. In HL-60 cells, cell death, apoptosis, ROS generation, and single/double DNA strand breaks induced by QDs were enhanced by treatment with curcumin and UVA irradiation. The protective effects of curcumin on cell viability, apoptosis, and ROS generation were observed in normal lymphocytes, but not leukemia cells. These results demonstrated that treatment with QD combined with curcumin increased cell death in HL-60 cells, which was mediated by ROS generation. However, curcumin acted as an antioxidant in cultured human normal lymphocytes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.12
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• pp.737-749
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• 2016

Recently perovskite materials with much cheaper cost and marvellous optoelectronic properties have been studied for next generation LED display devices overseas. Technology development trends of inorganic $CsPbX_3$(X=halogen) based LEDs (PeLEDs) with assumed high stability were investigated on literature worldwide. It was found that syntheses methods of these nanocrystals (NCs, mainly quantum dots, QDs) made great progress. A new room temperature synthesis method showed outstanding PL (photoluminescence) properties such as high quantum yield (QY), narrow emission width, storage stability comparable with, or often exceeding those of conventional hot injection method and CdSe@ZnS type inorganic colloidal QDs. PeLEDs with shell layers might be more promising, indicating urgent real research start of this solution processing technology for small businesses in Korea.

• Journal of the Korean Institute of Landscape Architecture
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• v.28 no.6
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• pp.29-51
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• 2001

The purpose of this research is to analyze of biotope structure focused on the evaluation for the species and biotope preservation in the case of Soosung District in Daegu metropolitan city. We analyzed the structure of urban biotope, and investigated the disposition of space and several characteristics through the material collection relating to the existing urban ecological material and the field investigation. The results of this study were as follows; 1) The result of biotope type classification was divided into 17 biotope type groups and 90 biotope types belonging to them. 2) The biotope type of mixed forest(QD) has the highest rate in occupation area, 1.764ha and the biotope type of cultivation areas by vinyle-hothouse(KC) has the lowest rate, 0.3ha. 3) In the result of the first evaluation for the species and biotope preservation, biotope types such as QB, QI, PA, PB, NB and NC etc. possess great value. Particulary, these biotope types come from forest areas and transition zone. They have not appeared in the inner of cities. 4) The biotope types such as CA, NA, NB, ND and PB are proved to possess high value in the result of rarity and riskiness evaluation. There appear EE, MA, NB, QC and QD in IV grade which is impossible to have them regenerative. They usually have appeared in forest areas. 5) There emerge 3a biotope type that has the highest value in the result of the second evaluation such as CC, EE, KF, LD, MB, NC, PB, QB and QI etc. Most of them were presented into the large area of site size and were distributed in the forest areas intensively. So, it is certain that the space for the species and biotope preservation connected with residential district is scarce. 6) The detailed biotope plan must be made out specially continuously. It is about biotope spaces that are especially important for the species and biotope preservation from the result of this research. Also, the study on the detailed index settlement of the urban landscape plan based on the biotope map must be continued.

• Journal of Sensor Science and Technology
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• v.29 no.2
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• pp.105-111
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• 2020

Interest and demand for hydrogen sensors are increasing in the field of H₂ leakage detection during storage/transport/use and detection of H₂ dissolved in transformer oil for safety issues as well as in the field of breath analysis for non-invasively diagnosing a number of disease states for a healthy life. In this study, various ZnO-based sensors were synthesized by controlling the reduction in crystallite size, decoration of Pt nanoparticles, doping of electron donating atoms, and doping of various atoms with different ionic radii. The sensing response of the various prepared ZnO-based nanoparticles and quantum dots (QDs) for 10 ppm H₂ was investigated. Among the samples, the smallest-sized (3.5 nm) In³⁺-doped ZnO QDs showed the best sensing response, which is superior to those in previously reported hydrogen sensors based on semiconducting metal oxides. The higher sensing response of In-doped ZnO QDs is attributed to the synergic effects of the increased number of oxygen vacancies, higher optical band gap, and larger specific surface area.

• Radiation Oncology Journal
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• v.19 no.4
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• pp.345-352
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• 2001

Purpose : To evaluate the treatment results and prognostic factors after radiotherapy in stage IIB uterine cervix cancer. Materials and methods : We retrospectively analyzed the records of 90 patients with stage IIB uterine cervix cancer who received radiotherapy between 9/94 and 12/99. Age was ranged from 28 to 79 years (median 57). Tumor size was $\geq4\;cm$ in 64 patients. Preteatment SCC level was measured in 75 patients. Twenty nine patients received conventional radiotherapy (QD) and the others received modified hyper-fractionated radiotherapy (BID). Only 7 patients in BID had tumor size <4 cm. All patients received high dose rate brachytherapy $(4\;Gy\times7\;or\;5\;Gy\times6)$. No Patient received concurrent chemotherapy during radiotherapy. Follow up period was ranging from 9 to 76 months (median 38). Results : The 5-year overall and disease free survival rates were $73.4\%\;and\;71.6\%$, respectively. Local recurrences occurred in $10\%$ of patients, and distant metastasis in $18.9\%$. There was a significant correlation between OS/DFS and tumor size $(<4cm;\;OS\;95.2\%,\;DFS\;91.4\%,\;\geq4cm;\;OS\;63.4\%,\;DFS\;63.4\%)$. Pretreatment SCC level was one of prognostic factors only in univariate analysis. Conclusion : With modified hyperfractionated radiotherapy, there was very low local recurrence rate $(6.6\%)$ and high 5-year overall and disease free survival rate $(75.4\%\;and\;70.5\%)$, which is comparable to results after concurrent chemoradiotherapy in bulky, locally advanced stage IIB uterine cervix cancer.

• 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.