• 한국진공학회지
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• 제20권6호
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• pp.436-441
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• 2011

각종 전자 방출원 및 디스플레이 응용 분야에서 뛰어난 가능성을 보이고 있는 탄소나노튜브의 전계 방출 특성을 개선하고 전자방출의 신뢰성을 개선하기 위해 탄소나노튜브의 표면에 수 nm 두께의 금속 코팅을 적용하였다. 탄소나노튜브는 실리콘 기판위에 2 nm 두께의 Invar (52% Fe, 42% Ni, 6% Co alloy) 촉매를 사용하여 $450^{\circ}C$의 온도에서 플라즈마 화학기상 증착법으로 성장시켰다. 성장된 탄소나노튜브의 밀도 제어를 위해 성장 후 질소 플라즈마로 일부를 식각한 후 티타늄(Ti) 금속을 탄소나노튜브 표면에 5~150 nm 두께로 스퍼터링 증착하였다. 5 nm로 티타늄을 탄소나노튜브 표면에 코팅한 경우, 코팅 전에 비해 6 V/${\mu}m$의 전계에서 전류밀도가 4배 이상 증가되었으며, 전계 방출 전류의 요동(fluctuation) 또한 40% 이상 감소됨을 확인할 수 있었다. 이는 티타늄의 일함수가 4.3 eV로 탄소나노튜브의 5 eV에 비해 작을 뿐만 아니라, 탄소나노튜브의 약점으로 지적되는 기판과의 접착성과 접촉저항이 티타늄의 표면 코팅으로 인해 크게 개선된 결과로 판단된다.

• Current Photovoltaic Research
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• 제7권4호
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• pp.125-129
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• 2019

Recently, carrier-selective contact solar cells have attracted much interests because of its high efficiency with low recombination current density. In this study, we investigated the effect of phosphorus doped amorphous silicon layer's characteristics on the passivation properties of tunnel oxide passivated carrier-selective contact solar cells. We fabricated symmetric structure sample with poly-Si/SiOx/c-Si by deposition of phosphorus doped amorphous silicon layer on the silicon oxide with subsequent annealing and hydrogenation process. We varied deposition temperature, deposition thickness, and annealing conditions, and blistering, lifetime and passivation quality was evaluated. The result showed that blistering can be controlled by deposition temperature, and passivation quality can be improved by controlling annealing conditions. Finally, we achieved blistering-free electron carrier-selective contact with 730mV of i-Voc, and cell-like structure consisted of front boron emitter and rear passivated contact showed 682mV i-Voc.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.148-148
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• 2015

Over the past several years, Colloidal core/shell type quantum dots lighting-emitting diodes (QDLEDs) have been developed for the future of optoelectronic applications. An inverted-type quantum-dot light-emitting-diode (QDLED), employing low work function organic material polyethylenimine ethoxylated(PEIE) (<10 nm)[1] modified ZnO nanoparticles (NPs) as electron injection and transport layer, was fabricated by all solution processing method, instead of electrode in the device. The PEIE surface modifier incorporated on the top of the ZnO NPs film, facilitates the enhancement of both electorn injection into the CdSe-ZnS QD emissive layer by lowering the workfunction of ZnO from 3.58eV to 2.87eV and charge balance on the QD emitter. In this inverted QDLEDs, blend of poly (9,9-di-n-octyl-fluorene-alt-benzothiadiazolo) and poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] are used as hole transporting layer (HTL) to improve hole transporting property. At the operating voltage of 7.5 V, the QDLED device emitted spectrally orange color lights with high luminance up to 11110 cd/m2, and showed current efficiency of 2.27 cd/A.[2]

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.18.1-18.1
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• 2011

Some applications of carbon nanotubes (CNTs) as field emitters, such as x-ray tubes and microwave amplifiers, require high current emission from a small emitter area. To emit the high current density, CNT emitters should be optimally fabricated in terms of material properties and morphological aspects including high crystallinity, aspect ratio, distribution density, height uniformity, adhesion on a substrate, low outgassing rate during electron emission in vacuum, etc. In particular, adhesion of emitters on the substrate is one of the most important parameters to be secured for high current field emission from CNTs. So, we attempted a novel approach to improve the adhesion of CNT emitters by incorporating metal oxide layers between CNT emitters. In our previous study, CNT emitters were fabricated on a metal mesh by filtrating the aqueous suspensions containing both highly crystalline thin multiwalled CNTs and thick entangled multiwalled CNTs. However, the adhesion of CNT film was not enough to produce a high emission current for an extended period of time even after adopting the metal mesh as a fixing substrate of the CNT film. While a high current was emitted, some part of the film was shown to delaminate. In order to strengthen the CNT networks, cobalt-nickel oxides were incorporated into the film. After coating the oxide layer, the CNT tips seemed to be more strongly adhered on the CNT bush. Without the oxide layer, the field emission voltage-current curve moved fast to a high voltage side as increasing the number of voltage sweeps. With the cobalt-nickel oxide incorporated, however, the curve does not move after the second voltage sweep. Such improvement of emission properties seemed to be attributed to stronger adhesion of the CNT film which was imparted by the cobalt-nickel oxide layer between CNT networks. Observed after field emission for an extended period of time, the CNT film with the oxide layer showed less damage on the surface caused by high current emission.

• 한국응용과학기술학회지
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• 제29권3호
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• pp.459-465
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• 2012

본 연구에서 7,7'-(2,2'dimethoxy-1,1'-binaphthyl-3,3'-diyl) bis(4-(thiophen-2-yl) benzo[e] [1,2,5] thiadiazole (TBT) 라는 binaphthyl기를 기반으로 가지는 녹색 도판트 물질을 합성하였다. 추가적으로 인광 발광 물질인 iridium(III)bis[(4,6-di-fluoropheny)-pyridinato -N,C2]picolinate (FIrpic)을 홀 수송용 호스트 물질인 N,N'-dicarbazolyl-3,5-benzene (mCP)에 도핑하고, TBT와 bis(2-phenylquinolinato)-acetylacetonate iridium(III) (Ir(pq)2acac)를 전자 수송용 호스트 물질인 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi)에 도핑하여 백색 빛을 발광하는 white organic light emitting diode (OLED)를 제작하였다. TBT를 사용하여 제작한 white OLED의 최대발광 효율과 외부 양자 효율은 각각 5.94 cd/A 과 3.23%를 나타냄을 알 수 있었다. Commission Internationale de I'Eclairage (CIE) 색 좌표의 값은 1000 nit에서 (0.34, 0.36)을 띄면서 순백색을 구현함을 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제31권8호
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• pp.2293-2298
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• 2010

Focused electrospray (FES) deposition method is presented for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. FES ion optics consists of two cylindrical focusing electrodes capped with a truncated conical electrode through which an electrospray emitter passes along the cylindrical axis. A spray of charged droplets is focused onto a sample well on a MALDI target plate under atmospheric pressure. The shape and size distributions of matrix crystals are visualized by scanning electron microscope and the mass spectra are obtained by time-of-flight mass spectrometry. Angiotensin II, bradykinin, and substance P are used as test samples, while $\alpha$-cyano-4-hydroxycinnamic acid and dihydroxybenzoic acid are employed as matrices. FES of a sample/matrix mixture produces fine crystal grains on a 1-3 mm spot and reproducibly yields the mass spectra with little shot-to-shot and spot-to-spot variations. Although FES greatly stabilizes the signals, the space charge due to matrix ions limits the detection sensitivity of peptides. To avoid the space charge problem, we adopted a dual FES/FES mode, which separately deposits matrix and sample by FES in sequence. The dual FES/FES mode reaches the detection sensitivity of 0.88 amol, enabling ultrasensitive of peptides by homogeneously depositing matrix and sample under atmospheric pressure.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.108-111
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• 2004

An efficiency and brightness of the Organic Light-emitting Diodes(OLEDs) by insertion of the novel layer between a singlet emitter and an electron transporting layer without doping processes, has been improved. The novel layers named as the K-M1 and K-M2 layers have shown the excellent improvement in the carrier balance and recombination efficiency. New devices using the K-M1 and K-M2 layers have shown a high efficiencies of over 15cd/A and 61m/W$(at\;20mA/cm^2)$, and brightness of over $16,000cd/m^2(at\;100mA/cm^2)$, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.51-51
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• 2008

Carbon nanotubes (CNTs) have long been reported as an ideal material due to their excellent electrical conductivity and chemical and mechanical stability as well as their high aspect ratios for field emission devices. CNT emitters made by screen printing the organic binder-based CNT paste may act as a source to release gases inside a vacuum panel. These residual gases may cause a catastrophic damage by electrical arcing or ion bombardment to the vacuum microelectronic devices and may change their physical or electrical properties by adsorbing on the CNT emitter surface. In this study, we analyzed the composition of residual gases inside the vacuum-sealed panel by residual gas analyzer (RGA), investigating the effects of individual gases of different kinds at several pressures on the field emission characteristics of CNT emitters. The residual gases included $H_2$, CO, $CO_2$, $N_2$, $CH_4$, $H_2O$, $C_2H_6$, and Ar. Effect of residual gases on the field emission was studied by observing the variation of the pulse voltages with the duty ratio of3.3% to keep the constant emission current of $28{\mu}A$. Each gas species was introduced to a vacuum chamber up to three different pressures ($5\times10^{-7}$, $5\times10^{-6}$, and $5\times10^{-5}$ torr) each for 1 h while electron emission was continued. The three different pressure regions were separated by keeping a high vacuum of $\sim10^{-8}$ torr for a 1 h. The emission was terminated 6 h after the third gas exposure was completed. Field emission characteristics under residual gases will be discussed in terms of their adsorption and desorption on the surface of CNTs and the resultant change of work function.

• 한국표면공학회지
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• 제38권4호
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• pp.163-166
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• 2005

Carbon nanotube-copper composite structures were fabricated using composite plating method and their field emission characteristics were investigated. Multi-walled carbon nanotubes (MWNTs) synthesized by chemical vapor deposition were used in the present study. It was revealed that turn-on field was about $3.0\;V/{\mu}m$ with the current density of $0.1\;{\mu}A/cm^2.$ We observed relatively uniform emission characteristics as well as stable emission current Carbon nanotube-copper composite plating method is efficient and it has no intrinsic limit on the deposition area. Moreover, it gives strong adhesion between emitters and an electrode. Therefore, we recommend that carbon nanotube-copper composite plating method can be applied to fabricate electron field emitters for large area FEDs and large area vacuum lighting sources.

• 한국전기전자재료학회논문지
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• 제29권3호
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• pp.181-185
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• 2016

One of the important issues for fabricating the microelectronic display devices such as FED, PDP, and VFD is to obtain a high vacuum level inside the panel. In addition, sustaining the initial high vacuum level permanently is also very important. In the conventional packing technology using a tabulation method, it is not possible to obtain a satisfiable vacuum level for a proper operation. In case of FED, the poor vacuum level results in the increase of operating voltage for electron emission from field emitter tips and an arcing problem, resultantly shortening a life time. Furthermore, the reduction of a sealing process time in the PDP production is very important in respect of commercial product. The most probable method for obtaining the initial high vacuum level inside the space with such a miniature and complex geometry is a vacuum in-line sealing which seals two glass plates within a high vacuum chamber. The critical solution for the vacuum sealing is to develop a frit glass to avoid the bubbling or crack problems during the sealing process at high temperature of about $400^{\circ}C$ under the vacuum environment. In this study, the suitable frit power was developed using a mixture of vitreous and crystalline type frit powders, and a vacuum sealed CNT FED with 2 inch diagonal size was fabricated and successfully operated.