• 마이크로전자및패키징학회지
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• 제11권2호
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• pp.11-16
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• 2004

전자칩의 고집적화에 의해 전자기기들은 점점 소형화 되어가고 있으며, 이들 기기들에서 발생되는 열은 기기의 성능 저하뿐 아니라 수명을 단축시킨다. 본 연구에서는 효율적인 방열 위한 마이크로 히트싱크 제조를 위하여 멤브레인에 금속(금, 니켈, 구리)은 도금하는 무전해 도금 방법을 이용하였다. 무전해 도금은 폴리카보네이트 멤브레인을 sensitization과 activation 등의 전처리 후, 도금하고자 하는 금속염 수용액에 침적시켜 실행하였다. 무전해 도금에 의하여 제조된 각각의 마이크로피브릴의 열전달 특성과 방열량은 표면적이 가장 큰 니켈 마이크로피브릴에서 가장 우수하게 나타났다.

• 한국재료학회지
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• 제4권5호
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• pp.516-523
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• 1994

이논문에서는 metal organic chemical vapor deposition(MOCVD)에 의해서 성장된 InGaAsP/InP이종접합구조의 격자부정합이 Photoluminescence(PL)효율에 미치는 영향을 연구하였다. 격자부정합은 (400)과 {511} x-ray reflection을 통해 측정하였고, 부정합 전위의 유무는 x-ray to-pography와 PL imaging을 통해 확인했다. PL강도 측정결과, 상대적으로 높은 PL강도는 탄성적으로 스트레인을 받은 시료에, 낮은 PL강도는 전위로 인해 비탄성적으로 변형된 시료에서 얻어졌다. 성장온도에서 격자정합된 시료의 PL효율이 실온에서 가장 높은 것을 알 수 있었다. PL강도와 X-ray반치폭과 관계에서, 시료의 광전자 특성이 구조적 특성과 밀접하게 연관됨을 알 수 있었다.

• 한국재료학회지
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• 제33권6호
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• pp.236-241
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• 2023

Solar cells based on p-conjugated donor-acceptor (D-A) organic molecular systems are a promising alternative to conventional electrical energy generation. D-A molecular systems, which have a triphenylamine (TPA) moiety linked with a benzothiadiazole (BTD) moiety, open the potential development of new small molecule donors for bulk heterojunction (BHJ) solar cells. Here, a series of donor-acceptor-π-acceptor (D-A-π-A) small molecule donors (SMD) derived from triphenylamine (TPA) donor and benzothiadiazole (BTD) acceptor building blocks, were designed for BHJ organic solar cells. The small molecule donors SMD1-4 were studied using density functional theory (DFT) and time dependent-DFT (TDDFT) methods, to understand the effect of cyano and fluorine group functionalization on their properties. The effect of structure alteration by cyano and fluorine group functionalization on the optoelectronic properties, the calculated highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs) and the HOMO-LUMO gaps were theoretically explored. The V_oc (open-circuit photovoltage) and fill factor (FF) for SMD1-4 were obtained with a PC₇₁BM acceptor, which showed that these organic small molecules are potential small molecule donors for organic bulk heterojunction solar cells.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2007년도 춘계학술발표대회 및 제12회 신소재 심포지엄
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• pp.30.2-30.2
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• 2007

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.237.2-237.2
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• 2011

SAW-ED를 이용하는 박막공정 기술을 통하여 나노레벨의 SWCNT 와 PEDOT의 thin film 및 hybrid화된 film구조를 얻을 수 있었다. SWCNT와 전도성고분자와의 hybridization을 통해 균일상의 표면 morphology를 갖는 고전도성 투명 필름을 제작하고, 이들의 전기광학적 성질을 확인하였다. SAW-ED를 이용하는 박막공정 기술은 나노입자 및 나노구조물의 박막화 패턴화를 포함하는 새로운 deposition 기술로서의 응용성을 가지고 있으며, 본 연구에서는 SWCNT와 전도성고분자를 이용하여 이를 확인하였다.

• 한국재료학회지
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• 제20권5호
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• pp.257-261
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• 2010

A non-volatile resistive random access memory (RRAM) device with a Cr-doped $SrZrO_3/SrRuO_3$ bottom electrode heterostructure was fabricated on $SrTiO_3$ substrates using pulsed laser deposition. During the deposition process, the substrate temperature was $650^{\circ}C$ and the variable ambient oxygen pressure had a range of 50-250 mTorr. The sensitive dependences of the film structure on the processing oxygen pressure are important in controlling the bistable resistive switching of the Cr-doped $SrZrO_3$ film. Therefore, oxygen pressure plays a crucial role in determining electrical properties and film growth characteristics such as various microstructural defects and crystallization. Inside, the microstructure and crystallinity of the Cr-doped $SrZrO_3$ film by oxygen pressure were strong effects on the set, reset switching voltage of the Cr-doped $SrZrO_3$. The bistable switching is related to the defects and controls their number and structure. Therefore, the relation of defects generated and resistive switching behavior by oxygen pressure change will be discussed. We found that deposition conditions and ambient oxygen pressure highly affect the switching behavior. It is suggested that the interface between the top electrode and Cr-doped $SrZrO_3$ perovskite plays an important role in the resistive switching behavior. From I-V characteristics, a typical ON state resistance of $100-200\;{\Omega}$ and a typical OFF state resistance of $1-2\;k{\Omega}$, were observed. These transition metal-doped perovskite thin films can be used for memory device applications due to their high ON/OFF ratio, simple device structure, and non-volatility.

• 한국표면공학회지
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• 제52권2호
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• pp.90-95
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• 2019

Methylammonium lead bromide ($MAPbBr_3$) has attracted a lot of attention due to their excellent optoelectronic properties such as the compositional flexibility relevant to photoluminescence (PL) and UV-Vis absorbance spectrum, high diffusion length, and photoluminescence quantum yield (PLQY). Despite such advantages of organic-inorganic perovskite materials, more systematic study on manipulation of their optoelectronic properties in homo- or heterovalent metal ions doped halide perovskite nanocrystals is lacking. In this study, we systematically investigated the optical properties of colloidal $CH_3NH_3Pb_{1-x}Sn_xCl_{2x}Br_{3-2x}$ particles by addition of $SnCl_2$ into the typical methylammonium lead tribromide ($CH_3NH_3PbBr_3$) precursor solution. We found that only 1% addition of $SnCl_2$ shows a significant blue-shift from 540 nm to 420 nm in UV-Vis absorbance spectrum due to the strong quantum confinement effect. Furthermore, continuous blue-shift in photoluminescence spectra was observed as the amount of Cl increases. These experimental results provide new insights into the replacement of Pb within $MAPbBr_3$, required for the broadening of their application.

• 한국광학회:학술대회논문집
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• 한국광학회 2004년도 하계학술발표회
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• pp.4-5
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• 2004

• Journal of the Korean Physical Society
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• 제73권10호
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• pp.1437-1443
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• 2018

In this work, $SnO_2$ modified with reduced graphene oxide (rGO) and carbon nanotubes (CNTs) separately and combined sensitized by using the co-precipitation method and their sensing behavior toward ethanol vapor at room temperature were investigated. An interdigitated electrode (IDE) gold substrate is very expensive compared to a fluorine doped tin oxide (FTO) substrate; hence, we used the latter to reduce the fabrication cost. The structure and the morphology of the studied materials were characterized by using differential thermal analyses (DTA) and thermogravimetric analysis (TGA), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller surface area and Barrett-Joyner-Halenda (BJH) pore size measurements. The studied composites were subjected to ethanol in its gas phase at concentrations from 10 to 200 ppm. The present composites showed high-performance sensitivity for many reasons: the incorporation of $SnO_2$ and CNTs which prevents the agglomeration of rGO sheets, the formation of a 3D mesopourus structure and an increase in the surface area. The decoration with rGO and CNTs led to more active sites, such as vacancies, which increased the adsorption of ethanol gas. In addition, the mesopore structure and the nano size of the $SnO_2$ particles allowed an efficient diffusion of gases to the active sites. Based on these results, the present composites should be considered as efficient and low-cost sensors for alcohol.

• 세라미스트
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• 제22권3호
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• pp.218-229
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• 2019

The development of highly efficient thermally activated delayed fluorescence (TADF) materials is an active area of recent research in organic light emitting diodes (OLEDs) since the first report by Chihaya Adachi in 2011. Traditional fluorescent materials can harvest only singlet excitons, leading to the theoretically highest external quantum efficiency (EQE) of 5% with considering about 20% light out-coupling efficiency in the device. On the other hand, TADF materials can harvest both singlet and triplet excitons through reverse intersystem crossing (RISC) from triplet to singlet excited states. It could provide 100% internal quantum efficiencies (IQE), resulting in comparable high EQE to traditional rare-metal complexes (phosphorescent materials). Thanks to a lot of efforts in this field, many highly efficient TADF materials have been developed. This review focused on recent molecular design concept and optoelectronic properties of TADF materials for high efficiency and long lifetime OLED application.