• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.182.2-182.2
• /
• 2015

최근 학계나 산업계에서 투명 전자 소자에 대하여 활발한 연구가 진행되면서, 투명 전 도성 산화물(TCO: transparent conductive oxide)에 대한 관심이 높아지고 있다. 대표적인 TCO 물질인 Indium Tin Oxide (ITO)는 가시 광 영역에서의 높은 투과 및 높은 도전성을 가져 전압을 인가하면 발열이 가능하므로 이를 투명 면상 발열체에 적용시키는 연구가 활발히 진행되고 있다. 하지만, ITO는 발열 테스트 결과 온도가 상승함에 따라 발열이 일부분에 집중되는 현상이 있으며, 전도성을 높이기 위하여 추가공정이 필요하다. 또한, 글라스의 곡면 부분에서 ITO를 사용하면 유연성이 부족하므로 크랙이 발생한다는 단점이 있다. 따라서, 최근 Silver nanowire (AgNW), Single-walled Carbon nanotube (SWCNT), ITO를 기반으로 한 AgNW에 ITO를 증착 하거나 SWCNT를 코팅하여 우수한 전기적, 광학적 특성을 지닌 하이브리드 전극이 투명 면상 발열체 재료로서 사용되고 있다. 하지만 대체된 재료들도 다양한 문제점을 가지고 있다. 예를 들어 고온에서 발열을 유지하지 못하고 끊어지거나 가시광영역의 투과율이 낮은 점 등이 있다. 이런 다양한 문제점들을 보완 할 수 있는 새로운 투명 면상 발열체에 적용한 연구가 요구되고 있다. 본 연구에서는 GZO/Ag/GZO 하이브리드 구조의 투명 면상 발열체를 제작하여 전기적, 광학적 특성을 비교하고 발열량, 온도 균일 성, 발열 유지 안정도를 확인하였다. 본 연구에서는 $50{\times}50mm$ 크기의 Non-alkali glass (삼성코닝 E2000) 기판 상에 DC마그네트론 스퍼터링 공정을 이용하여 상온에서 GZO, Ag, GZO 박막을 연속적으로 증착 하여 다층구조의 하이브리드형 투명 면상 발열체를 제조하였다. 박막 증착 파워는 DC (Ag) power 50 W, RF (GZO) power 200 W로 하였으며 GZO박막두께는 45 nm로 고정 시키고 Ag박막 두께는 5~20 nm로 변화를 주었다. 증착원은 3인치 GZO 세라믹 타깃 (2.27 wt. % Ga2O3) 과 Ag 금속 타깃 (순도 99.99%)을 사용하였으며, Ar을 40 sccm 주입 후 Working pressure는 고 순도 Ar을 사용하여 1.0 Pa로 고정하며 10분간 Pre-sputtering을하고 증착을 진행하였다. 앞선 실험을 통해 증착한 박막의 전기적, 광학적 특성은 각각 Hall-effect measurements system (ECOPIA, HMS3000), UV-Vis spectrophotometer (UV-1800, Shimadzu)를 사용해 측정 되었으며, 하이브리드 표면의 구조 및 형상은 FESEM으로 관찰하였다. 또한 표면온도 측정기infrared camera (IR camera)를 이용하여 4~12 V/cm의 전압을 인가 시 시간에 따른 투명 면상 발열체의 표면 온도변화를 관찰하였다.

• Korean Journal of Materials Research
• /
• v.21 no.5
• /
• pp.273-276
• /
• 2011

Ultraviolet (UV) light emitting diodes (LEDs) were grown on a patterned n-type GaN substrate (PNS) with 200 nm silicon-di-oxide (SiO2) nano pattern diameter to improve the light output efficiency of the diodes. Wet etched self assembled indium tin oxide (ITO) nano clusters serve as a dry etching mask for converting the SiO2 layer grown on the n-GaN template into SiO2 nano patterns by inductively coupled plasma etching. PNS is obtained by n-GaN regrowth on the SiO2 nano patterns and UV-LEDs were fabricated using PNS as a template. Two UV-LEDs, a reference LED without PNS and a 200 nm PNS UV-LEDs were fabricated. Scanning Electron microscopy (SEM), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), Photoluminescence (PL) and Light output intensity- Input current- Voltage (L-I-V) characteristics were used to evaluate the ITO-$SiO_2$ nanopattern surface morphology, threading dislocation propagation, PNS crystalline property, PNS optical property and UVLED device performance respectively. The light out put intensity was enhanced by 1.6times@100mA for the LED grown on PNS compared to the reference LED with out PNS.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.1096_1097
• /
• 2009

Aluminium doped zinc oxide(ZnO:Al) thin film, which is mainly used as a transparent conducting electrode in electronic devices, has many advantages compared with conventional indium tin oxide(ITO). In this paper in order to investigate the possible application of ZnO:Al thin films as a transparent conducting electrode for flexible film-typed dye sensitized solar cell (FT-DSCs), ZnO:Al and ITO thin films were prepared on the polyethylene terephthalate (PET) substrate by r. f. magnetron sputtering method. Specially one-inched FT-DSCs using either a ZnO:Al or ITO electrode were also fabricated separately under the same manufacturing conditions. Some properties of both the FT-DSCs with ZnO:Al and ITO transparent electrodes, such as conversion efficiency, fill factor, and photocurrent were measured and compared with each other. The results showed that by doping the ZnO target with 2 wt% of $Al_2O_3$, the film deposited at discharge power of 200W resulted in the minimum resistivity of $2.2\times10^{-3}\Omega/cm$ and at ransmittance of 91.7%, which are comparable with those of commercially available ITO. Two types of FT-DSCs showed nearly the same tendency of I-V characteristics and the same value of conversion efficiencies. Efficiency of FT-DSCs using ZnO:Al electrode was around 2.6% and that of fabricated FT-DSCs using ITO was 2.5%. This means that ZnO:Al thin film can be used in FT-DSCs as a transparent conducting layer.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.67 no.1
• /
• pp.68-74
• /
• 2018

All transparent UV photodetector based on ZnO was fabricated with structure of NiO/ZnO/$SnO_2$/ITO by using RF and DC magnetron sputtering system. ZnO was deposited with 4 inch ZnO target (purity 99.99%) for a quality film. In order to build p-n junction up, p-type NiO was formed on n-type ZnO by using reactive sputtering method. The indium tin oxide (ITO) which is transparent conducting oxide (TCO) was applied as a transparent electrode for transporting electrons. To improve the UV photodetector performance, a functional $SnO_2$ layer was selected as an electron transporting and hole blocking layer, which actively controls the carrier movement, between ZnO and ITO. The photodetector (NiO/ZnO/$SnO_2$/ITO) shows transmittance over 50% as similar as the transmittance of a general device (NiO/ZnO/ITO) due to the high transmittance of $SnO_2$ for broad wavelengths. The functional $SnO_2$ layer for band alignment effectively enhances the photo-current to be $15{\mu}A{\cdot}cm^{-2}$ (from $7{\mu}A{\cdot}cm^{-2}$ of without $SnO_2$) with the quick photo-responses of rise time (0.83 ms) and fall time (15.14 ms). We demonstrated the all transparent UV photodetector based on ZnO and suggest the route for effective designs to enhance performance for transparent photoelectric applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.55-55
• /
• 2008

압전폴리머 PVDF(polyvinylidene difluoride)의 기판소재를 기반으로 한 디스플레이 소자를 연구하였다. 압전 폴리머 PVDF의 양면은 두께 300nm정도의 ITO(Indium Tin Oxide)를 TCO(Transparent conducting oxide)로 R2R(roll to roll)증착하였으며, 이를 적외선 계열 Pulsed Laser로 상온 건식 에칭을 통해 패턴해내고, 이후 고진공 환경에서 Alq3 를 기반의 유기발광소자를 제작하였다. 전기적 신호에 대해서 기계적인 작동이 가능한 투명 압전 폴리머 재료를 디스플레이 발광소자의 기판 소재로 사용함으로써, 궁극적으로 발광기능과 더불어 압전효과에 의한 스피커 기능이 한 개의 개체내에서 독립적으로 구현될 수 있도록 설계하고, 기술적으로 실현시켰다는 점이 본 연구의 의의라고 할 수 있다. 이를 위해서, 섭씨 80도 이상의 온도에서 압전 성질을 상실하는 것으로 알려진 PVDF에 대해서 투명산화전극을 레이져를 이용한 비가열식 승화방법을 통해 패턴화하는 것을 사용했으며, 밀리미터 단위에서 수십 마이크로미터 수준까지 패턴화할 수 있었다. 제작된 복합형 유연 OLED소자는 기계적으로 휘어진 상태에서도 발광 성능과 스피커 성능을 각각 독립적으로 보였으며, Alq3에 의한 녹색발광을 보임을 확인하였고, 이 경우 양자효율은 약 3%이하의 값을 보였다. 또한 각주파수별 음압(SPL: Sound Pressure Level)측정 결과는 압번폴리머가 가청주파수 영역에서 작동함을 보였으며, 고주파영역에서의 SPL값이 증가하는 전형적인 PVDF사용 필름 스피커의 특성을 보였다. 이로부터 제작된 복합형 소자는 본 연구에서 제안된 목적에서 보인 것과 같이, 두 개의 기능이 서로간의 간섭없이 독립적으로 한 개의 개체 내에서 작동함을 확인할 수 있었다. 본 연구 결과로부터 새로운 유연 전자 소자에 대한 디자인 개념을 제시하고, 기타 다른 기능이 접합된 형태의 신개념 전자 소자를 제안하는 것도 가능할 것으로 기대된다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.300-300
• /
• 2008

In this study, the advanced DuoPIGatron-type ion beam (IB) system was applied to inorganic thin film for aligning liquid crystal (LC). LC alignment on $Ta_2O_5$ via IB irradiation was embodied. As a result of IB irradiation, the homogeneously aligned liquid crystal display (LCD) on $Ta_2O_5$ was observed with low pretilt angles. The $Ta_2O_5$ were deposited on indium-tin-oxide coated Coming 1737 glass substrates by rf magnetron sputtering at $200^{\circ}C$. The deposition process resulted in forming very uniform thin film on glass substrates without any defects. To confirm the application of the inorganic alignment on modem display optical devices, we fabricated twisted nematic LCD and measured optical property and response time. As a result of the experiment, the electro optical characteristics of the LCD fabricated by using IB irradiation on $Ta_2O_5$ alignment layer were similar with the other LCD fabricated by using rubbing process.

• Journal of Sensor Science and Technology
• /
• v.20 no.3
• /
• pp.156-161
• /
• 2011

We fabricated a schottky barrier metal oxide semiconductor field effect transistor(SB-MOSFET) by applying indium-tin-oxide(ITO) to the source/drain on a highly resistive GaN layer grown on a silicon substrate. The MOSFET, with 10 ${\mu}M$ gate length and 100 ${\mu}M$ gate width, exhibits a threshold gate voltage of 2.7 V, and has a sub-threshold slope of 240 mV/dec taken from the $I_{DS}-V_{GS}$ characteristics at a low drain voltage of 0.05 V. The maximum drain current is 18 mA/mm and the maximum transconductance is 6 mS/mm at $V_{DS}$=3 V. We observed that the spectral photo-response characterization exhibits that the cutoff wavelength was 365 nm, and the UV/visible rejection ratio was about 130 at $V_{DS}$ = 5 V. The MOSFET-type UV detector using ITO, has a high UV photo-responsivity and so is highly applicable to the UV image sensors.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.246.1-246.1
• /
• 2014

Over the past several years, colloidal core/shell type quantum dots lighting-emitting diodes (QDLEDs) have been extensively studied and developed for the future of optoelectronic applications. In the work, we fabricate an inverted CdSe/ZnS quantum dot (QD) based light-emitting diodes (QDLED). In order to reduce work function of indium tin oxide (ITO) electrode for inverted structure, a very thin (<10 nm) polyethylenimine ethoxylated (PEIE) is used as surface modifier[1] instead of conventional metal oxide electron injection layer. The PEIE layer substantially reduces the work function of ITO electrodes which is estimated to be 3.08 eV by ultraviolet photoemission spectroscopy (UPS). From transmission electron microscopy (TEM) study, CdSe/ZnS QDs are uniformly distributed and formed by a monolayer on PEIE layer. 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 8 V, the QDLED device emitted spectrally orange color lights with high luminance up to 2450 cd/m2, and showed current efficacy of 0.6 cd/A, respectively.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.432.2-432.2
• /
• 2014

Recently, colloidal core/shell type quantum dots lighting-emitting diodes (QDLEDs) have been extensively studied and developed for the future of optoelectronic applications. In the work, we fabricate an inverted CdSe/ZnS quantum dot (QD) based light-emitting diodes (QDLED)[1]. In order to reduce work function of indium tin oxide (ITO) electrode for inverted structure, a very thin (<10 nm) polyethylenimine ethoxylated (PEIE) is used as surface modifier[2] instead of conventional metal oxide electron injection layer. The PEIE layer substantially reduces the work function of ITO electrodes which is estimated to be 3.08 eV by ultraviolet photoemission spectroscopy (UPS). From transmission electron microscopy (TEM) study, CdSe/ZnS QDs are uniformly distributed and formed by a monolayer on PEIE layer. In this inverted QD LED, two kinds of hybrid organic materials, [poly (9,9-di-n-octyl-fluorene-alt-benzothiadiazolo)(F8BT) + poly(N,N'-bis (4-butylphenyl)-N,N'-bis(phenyl)benzidine (poly-TPD)] and [4,4'-N,N'-dicarbazole-biphenyl (CBP) + poly-TPD], were adopted as hole transport layer having high highest occupied molecular orbital (HOMO) level for improving hole transport ability. At a low-operating voltage of 8 V, the device emits orange and red spectral radiation with high brightness up to 2450 and 1420 cd/m2, and luminance efficacy of 1.4 cd/A and 0.89 cd/A, respectively, at 7 V applied bias. Also, the carrier transport mechanisms for the QD LEDs are described by using several models to fit the experimental I-V data.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.590-590
• /
• 2012

A transparent conducting oxide (TCO) layer was applied in crystalline Si (c-Si) solar cells without use of the conventional SiNx-coating. A high quality indium-tin-oxide (ITO) layer was directly deposited on an emitter layer of a Si wafer. Three different types of emitters were formed by controlling the phosphorous diffusion condition. A light-doped emitter forming a thinner emitter junction showed an improved photoconversion efficiency of 14.1% comparing to 13.2% of a heavy-doped emitter. This was induced by lower recombination within a narrower depletion region of the light-doped emitter. In the aspect of light management, the intermediate refractive index of ITO is effective to reduce the light reflection leading the enhanced carrier generation in a Si absorber. For the electrical aspect, the ITO layer serves as an efficient electrical conductor and thus relieves the burden of high contact resistance of the light-doped emitter. Additionally, the ITO works as a buffer layer of Ag and Si and certainly prevents the shunting problem of Ag penetration into Si emitter region. It discusses an efficient design scheme of TCO-embedded emitter Si solar cells.