• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.439-439
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• 2012

ZnO 나노로드는 큰 밴드갭 에너지(~3.37 eV)와 60 meV의 높은 엑시톤 결합 에너지(exciton binding energy)를 갖고 있으며, 우수한 전기적, 광학적 특성을 지닌 1차원 나노구조의 금속산화물로서 태양전지 및 광전소자 널리 응용되고 있다. 이러한 ZnO 나노로드를 성장하는 방법 중에 전기화학증착법(electrochemical deposition method)은 전도성 물질위에 증착된 시드층(seed layer)을 성장용액에 담그어 전압을 인가하여 만들기 때문에 기존의 수열합성법(hydrothermal method), 졸-겔 법(sol-gel method)보다 비교적 간단한 공정과정으로 저온에서 빠르게 물질을 성장시킬 수 있는 장점이 있다. 한편, 디스플레이 산업에서 ITO (indium tin oxide)는 투명 전도성 산화물(transparent conductive oxide)로써 가시광 파장영역에서 높은 투과율과 전도성을 가지며, 액정디스플레이, LED (Light emitting diode), 태양전지 등의 다양한 소자에 투명전극 재료로 쓰이고 있다. 또한 최근 ITO를 유연한 PET (polyethylene terephthalate) 기판 위에 증착은 얇고, 가볍고, 휘어지기 쉬워 휴대하기 편하기 때문에 차세대 광전자소자 응용에 가능성이 크다. 본 연구에서는 ZnO 나노로드를 ITO/PET 기판위에 전기화학증착법으로 성장하여, 구조적 및 광학적 특성을 분석하였다. 시드층을 형성하기 위해 RF 마그네트론 스퍼터를 이용하여 ~20 nm 두께의 ZnO 박막을 증착시킨 후, zinc nitrate와 hexamethylenetetramine이 포함된 수용액에 시료를 담그어 전압을 인가하였다. 용액의 농도와 인가전압을 조절하여 여러 가지 성장조건에 대한 ZnO 나노로드의 구조적, 광학적 특성을 비교하였다. 성장된 시료의 형태와 결정성을 조사하기 위해, field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD)을 사용하였으며, UV-vis-NIS spectrophotometer, photoluminescence (PL) 측정장비를 사용하여 광학적 특성을 분석하였다.

• Laser Solutions
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• v.17 no.1
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• pp.1-6
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• 2014

Indium tin oxide (ITO) is an important transparent conducting oxide (TCO). ITO films have been widely used as transparent electrodes in optoelectronic devices such as organic light-emitting devices (OLED) because of their high electrical conductivity and high transmission in the visible wavelength. Finding ways to control ITO micromachining depth is important role in the fabrication and assembly of display field. This study presented the depth control of ITO patterns on glass substrate using a femtosecond laser and slit. In the proposed approach, a gaussian beam was transformed into a quasi-flat top beam by slit. In addition, pattern of square type shaped by slit were fabricated on the surfaces of ITO films using femtosecond laser pulse irradiation, under 1030nm, single pulse. Using femtosecond laser and slit, we selectively controlled forming depth and removed the ITO thin films with thickness 145nm on glass substrates. In particular, we studied the effect of pulse number on the ablation of ITO. Clean removal of the ITO layer was observed when the 6 pulse number at $2.8TW/cm^2$. Furthermore, the morphologies and fabricated depth were characterized using a optical microscope, atomic force microscope (AFM), and energy dispersive X-ray spectroscopy (EDS).

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.299-299
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• 2013

Indium Tin Oxide (ITO) has widely been used as a transparent conductive oxide (TCE) for photovoltaic devices. Lately, flexibility of ITO becomes an issue as demand of flexible device increases. Several scientists have tried to substitute ITO to different materials such as conductive polymer, graphene, CNT, and metal nanowire because of ITO brittleness. Among the substitute materials, PEDOT:PSS has mostly paid attention because PEDOT:PSS has excellent flexibility and good conductivity. The conductivity of PEDOT:PSS increases up to 1000 S/cm with additives such as DMSO, EG, sorbitol, and so on. In our research group, we introduce a conductive polymer PEDOT:PSS as a buffer layer to improve not only flexibility but also conductivity. As PEDOT:PSS layer forms beneath ITO thin film (20 nm), sheet resistance decreases from $230{\Omega}$/${\Box}$ to $85{\Omega}$/${\Box}$ and crack initiation decreases from 4.5 mm to 3.5 mm as well. We have fabricated organic photovoltaic device and power conversion efficiencies using conventional ITO electrode and ITO/PEDOT:PSS hybrid electrode. The photovoltaic property such as power conversion efficiency for ITO/PEDOT:PSS hybrid electrode is comparable to the value obtained using conventional ITO electrode on glass substrate.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.5
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• pp.319-325
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• 1999

Direct current(d.c.)leakage current voltage characteristics of radio-frequencymagnetron sputtered BaTa\sub 2\O\sub 6\ film capacitors with aluminum(A1) top and indium tin oxide (ITO) bottom electrodes have been investigatedas a function of applied field and temperature. In order to study surfacetreatment effect on the electrical characteristics of as-deposited film weperformed exposure of oxygen plasma on $BaTa_2O_6$ surface. d. c.current-voltage (I-V), bipolar pulse charge-voltage (Q-V), d. c. current-time (I-t) andcapacitance-frequency (C-f) analysis were performed on films. All ofthe films exhibita low leakage current, a high breakdown field strength (3MV/cm-4.5MV/cm), and high dielectric constant (20-30). From the temperature dependence of leakage current,we can conclude that the dominant conduction mechanism is ascribed toSchottky emission at high electric field (>1MV/cm) and hopping conduction at lowelectric field (<1MV/cm). According to our results, the oxide plasma surfacetreatmenton as-deposited $BaTa_2O_6$ resulted in lowering interfacebarrier height and thus, leakage current when a negative voltage applied to the A1 electrode. This can be explained by reduction of surface contamination via etching surface and filling defects such as oxygen vacancies.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.380-381
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• 2007

This paper reports on the deposition conditions and properties of ITO films used as electrode layer in a organic light emitting diodes on a PET substrate. The deposition technique employed was specially designed roll-to-roll sputtering. The oxide was deposited at room temperature in an argon and oxygen plasma on a transparent conducting ITO layer on a PET film. The influence of deposition parameters such as DC power, working pressure and oxygen partial pressure has been investigated, in order to obtain the best compromise between a high deposition rate and adequate electro-optical properties. Electrical and optical properties of ITO films were analyzed by Hall measurement examinations with van der pauw geometry at room temperature and UV/Vis spectrometer analysis, respectively. In addition, the structural properties and surface smoothness were measured by x-ray diffraction and scaning electron microscopy, respectively. From optimized ITO films grown by roll-to-roll sputter system, good electrical$(6.44{\times}10^{-4}\;{\Omega}-cm)$ and optical(above 86 % at 550 nm) properties were obtained. Also, the ITO films exhibited amorphous structure and very flat surface beacause of low deposition temperature.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.120-120
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• 2010

최근 투명전도성 산화물(Transparent Conductive Oxide, TCO) 박막은 액정 표시소자(LCD), 플라즈마 디스플레이 패널(PDP), 압전소자 및 태양전지의 투명소자로 사용되어지고 있다. 현재 가장 널리 사용되어지고 있는 투명전극물질인 인듐주석산화물(indium tin oxide, ITO)은 낮은 비저항과 높은 투과율을 가지고 있지만, 높은 원자재의 가격 및 수소플라즈마 처리시 In과 Sn이 환원되어 전기적, 광학적으로 불안정한 문제점들이 지적되고 있다. 이러한 문제점들을 해결하기 위해 최근 적외선 및 가시광선 영역에서 높은 투과도 및 전기 전도성과 수소플라즈마에 대한 화학적 안정성을 갖는 ZnO를 기반으로 3족 원소를 첨가한 새로운 투명 전도막에 대한 연구가 활발하다. 본 연구에서는 RF-Magnetron Sputtering법을 이용하여 $Ga_2O_3$ 혼합비에 따라 제작된 ZnO(GZO) 박막들의 전기적, 광학적, 구조적인 특성들을 분석하였다. 측정결과, $Ga_2O_3$의 첨가량이 7 wt.%인 GZO 박막이 가시광선영역에서 80%이상의 높은 투과율과 $50.5\;\Omega/\Box$의 가장 낮은 면저항을 나타내었다. 이는 Ga원소가 다른 3족 원소와 격자결합을 비교할 때, 이온의 크기가 Zn원소와 비슷하여 최적화된 혼합율을 가지는 경우 격자결합을 최소화시켜 캐리어 밀도의 증가로 인해 높은 전도성을 가지며, 고온에서도 전기적 특성 및 내구성이 향상되기 때문이다. 또한 기판온도에 따른 열처리 특성으로서 기판의 온도를 $100^{\circ}{\sim}400^{\circ}C$까지 변화를 주어 실험하였다. X-선 회절패턴 분석결과 기판온도가 증가함에 따라 ZnO (002) 방향이 감소하는 반면 ZnO(103) 방향이 증가하였으며, 기판온도가 $300^{\circ}C$ 일 때 $17.1\;\Omega/\Box$의로 가장 낮은 면저항이 나타났다. 이는 SEM 이미지를 분석한 결과, 실온에서 제작된 박막과 비교해 300 에서 증착된 GZO 박막이 결정립의 크기가 크고 밀도도 조밀해져 전하의 이동도가 향상되었기 때문이다.

• Journal of Sensor Science and Technology
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• v.31 no.6
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• pp.455-460
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• 2022

Brush-like ZnO hierarchical nanostructures decorated with MgxZn1-xO (x = 0.1, 0.2, 0.3, 0.4, and 0.5) were fabricated and examined for application to a gas sensor. They were synthesized using vapor phase growth (VPG) on indium tin oxide (ITO) substrates. To generate electronic accumulation at ZnO surface, MgZnO nanoparticles were prepared by sol-gel method, and the ratio of Mg and Zn was adjusted to optimize the device for NO₂ gas detection. As the electrons in the accumulation layer generated by the heterojunction reacted faster and more frequently with the gas, the sensitivity and speed improved. When tested as sensing materials for gas sensors at 100 ppm NO₂ at 300℃, these MgZnO decorated ZnO nanostructures exhibited an improvement from 165 to 514 times compared to pristine ZnO. The response and recovery time of the MgZnO decorated ZnO samples were shorter than those of the pristine ZnO. Various analyzing techniques, including field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray powder diffraction (XRD) were employed to confirm the growth morphology, atomic composition, and crystalline information of the samples, respectively.

• Journal of Sensor Science and Technology
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• v.31 no.2
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• pp.90-95
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• 2022

The effect of the structure of an ITO nanoparticle film sensor on its performance was studied. A printed ITO film (P-ITO film) was fabricated on a flexible polyethylene terephthalate (PET) substrate, and the contact resistance of the electrode and sensor response change were clarified according to the detection position. The contact resistance between Ag and P-ITO was observed to be -204.4 Ω using the transmission line method (TLM), confirming that a very good ohmic contact is possible. In addition, we confirmed that the contact position of the analyte had a significant influence on the response of the sensor. Based on these results, the performance of the four types of sensors was compared. Consequently, we observed that 1) optimizing the resistance of the printed film, 2) optimizing the electrode structure and analyte input position, and 3) optimizing the electrode area are very important for fabricating a metal oxide nanoparticle (MONP) sensor with optimal performance.

• Journal of Sensor Science and Technology
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• v.31 no.3
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• pp.163-167
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• 2022

In this study, we investigated a carbon nanotube (CNT) film sensor to detect hazardous and noxious substances distributed in seawater. The response change of the sensor was studied according to environmental temperature, and its temperature coefficient of resistance (TCR, α) was measured. The temperature of the CNT film (~50 ㎛) was in the range of 20-50 ℃, and αCNT was calculated to be -0.0011 %/ ℃. We experimentally confirmed that the CNT film had a smaller TCR value than that of the conventional sensor. Therefore, we investigated the response change of the CNT sensor according to temperature. The CNT sensor showed a relatively small error of approximately 2.3 % up to 30 ℃, which is within the temperature range of the seawater of the Korean Peninsula. However, when the temperature exceeded 40 ℃, the error in the CNT sensor increased by more than 5.2 %. We fabricated a metal oxide (ITO, indium-tin-oxide) film and compared its performance with that of the CNT sensor. The ITO sensor showed an error of >12.5 % at 30 ℃, indicating that in terms of the stability of the sensor to temperature, the CNT film sensor has superior performance.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.1 s.38
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• pp.51-55
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• 2006

The green emitting high performance OLEDs using the $Alq_3$-C545T fluorescent system have been fabricated and characterized. In the device fabrication, 2-TNATA [4,4',4'-tris(2-naphthylphenyl-phenylamino)-triphenylamine] as a hole injection material and NPB [N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine] as a hole transport material were deposited on the ITO(indium thin oxide)/glass substrate by vacuum evaporation. And then, green color emission layer was deposited using $Alq_3$ as a host material and C-545T[10-(2-benzothiazolyl)-1,1,7,7- tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-[1]/benzopyrano[6,7,8-ij]-quinolizin-11-one] as a dopant. Finally, small molecule OLEDs with structure of ITO/2-TNATA/NPB/$Alq_3$:C545T/$Alq_3$/LiF/Al were obtained by in-situ deposition of $Alq_3$, LiF and Al as the electron transport material, electron injection material and cathode, respectively. Green OLEDs fabricated in our experiments showed the color coordinate of CIE(0.29, 0.65) and the maximum power efficiency of 7.3 lm/W at 12 V with the peak emission wavelength of 521 nm.