• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.62.1-62.1
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• 2011

현재 상용화된 LED 또는 태양전지 등의 투명전극(TCO, transparent couducting oxide)재료로 높은 전기전도도와 광투과도를 갖는 ITO (Indium Tin Oxide)가 많이 채택되고 있다. 그러나 이에 사용되는 Indium의 단가가 높다는 문제점이 있어 이를 대체하기 위한 물질의 연구가 많이 이루어지고 있다. 특히 Aluminum을 doping한 ZnO (AZO)는 우수한 전기적, 광학적 특성 등으로 인해 ITO를 대체할 차세대 TCO 물질로 각광받고 있다. 본 연구에서는 sol-gel법을 및 direct patterning법을 이용하여 moth-eye 패턴을 포함하는 AZO 박막을 제작하였다. AZO sol을 제작하기 위하여 2-methoxyethanol, zinc acetate dihydrate 및 doping source로 aluminum nitrate nonahydrate를 사용하였다. 또한 광추출 향상 효과를 갖는 moth-eye 구조의 master stamp를 Polydimethyl siloxane(PDMS)를 이용하여 역상 moth-eye 구조의 mold를 복제하였으며, 이 복제된 mold와 제작된 AZO sol을 이용한 direct patterning법을 통해 나노급 moth-eye 구조를 갖는 AZO 투명전극층을 형성하였다. 제작된 moth-eye 구조를 갖는 AZO 투명전극층의 전기적 특성 평가를 위해, 4-point probe 측정 및 Hall measurement를 시행하였으며, 광학적 특성을 확인하기 위하여 UV-Visable spectrometer를 이용하여 투과도를 측정하였다. 본 연구를 통해 현재 상용화된 광전자 소자에 사용되고 있는 ITO 투명전극을 대체할 차세대 투명전극으로써 AZO 박막의 가능성을 확인하였다.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1564-1567
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• 2005

Zinc oxide thin films were grown at the t emperature of $100^{\circ}C$ and $150^{\circ}C$ by means of plasma enhanced atomic layer deposition (PEALD) and conventional atomic layer deposition for applying to the transparent thin film transistor (TTFT). The growth rate of $1.9{\AA}/cycle$ with oxygen plasma is similar to that of film grown with water. While the sheet resistivity of ZnO grown with water is 1233 ohm/sq, that of film grown with oxygen plasma was too high to measure with 4 point probe and hall measurement system. The resistivity of the films grown with oxygen plasma estimated to be $10^6$ times larger than that of the films grown with water. The difference of electrical property between two films was caused by the O/Zn atomic ratio. We fabricated ZnO-TFT by means of ALD for the first time and the ZnO channel fabricated with water showed saturation mobility of $0.398cm^2/V{\cdot}s$ with bottom gate configuration.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.247-247
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• 2008

In this work, VOx thin films have been deposited by DC magnetron sputtering method on glass substrate using argon and oxygen gases. We examined the effects of the post annealing temperature on the structural, optical, and electrical variations of VOx films. The films were annealed at temperatures ranging from 300 to $500^{\circ}C$ in steps of $100^{\circ}C$ using RTA equipment in air ambient. The thickness of the film and interface between film and substrate were observed by field emission scanning electron microscopy (FESEM). To analysis the structural properties of VOx with various annealng temperatures, we used XRD method. Also, we investigated the electrical and optical properties of VOx thin films using hall measurement, 4-point probe, and UV-visible methods.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.100-100
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• 1999

가시광선 영역에서 높은 광학적 투과성과 함께 우수한 전기 전도성을 갖는 ITO 박막은 디스플레이 소자나 투명전극재료 등 다양한 분야에서 응용성이 더욱 증대되고 있다. 증착기판으로서 유리를 사용할 때 생기는 활용범위 제한을 극복하고자 최근 유기물 위에 증착이 가능한 저온 증착방법에 대한 연구가 활발히 이루어지고 있다. 그 가운데 이온빔과 같은 energetic한 beam을 이용한 박막의 제조는 기판을 플라즈마 발생지역으로부터 분리시켜 이온빔의 flux 및 에너지, 입사각 등의 자유로운 조절을 통해 상온에서도 우수한 성질의 박막 형성 가능성이 제시되어 왔다. 본 연구에서는 ion beam assisted evaporation방법을 이용하여 ITO 박막을 성장시켰으며, ion-surface interaction 효과가 박막 성장주에 미치는 영향을 이해하기 위하여 먼저 반응성 산소 이온빔에 비 반응성 아르곤 이온빔을 다양하게 변화시켜가며 증착하였으며, 이와 더불어 산소 분위기에서 아르곤 이온빔에 의한 ITO 박막의 특성 변화를 각각 관찰하였다. 증착전 후의 열처리 없이 상온에서 비저항이 ~10-4$\Omega$cm 이하로 낮고 80% 이상의 투과율을 갖는 ITO 박막을 성장시켰다. 실험에서 이용된 e-beam evaporation 물질은 In2O3-SnO2(1-wt%)였으며, 이온빔 source는 산소에 의한 filament의 산화를 막기 위해 filament cathodes type이 아닌 rf(radio-frequency)를 사용하였다. 중요 증착변수인 이온빔의 flux 변화는 산소와 Ar의 flow rate를 MFC로 조절하고 rf power를 변화시켜 얻었으며, 이온빔 에너지는 가속 grid의 가속전압 변화와 ion gun과 기판사이의 거리 조절을 통해 최적화하였다. 이온빔의 에너지와 flux는 Faraday cup으로 측정하였으며, 성박된 박막의 특성은 UV-spectrometer, 4-point probe, Hall measurement. $\alpha$-step, XRD, XPS 등을 이용하여 광학적, 전기적, 구조적 특성을 분석하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.581-581
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• 2013

ITO (Indium Tin oxide)는 비화학 양론적 조성을 띄는 n-type 반도체 특성이 있으며 가시광 영역(380~780 nm)의 파장에 대한 높은 광 투과도(>85%)를 가지며 비교적 높은 전도도(${\sim}10^4/{\Omega}-cm$)를 갖고 화학적 안정성이 우수하여 투명전극 박막으로 많이 사용되어왔다. 또한, PET film은 전기절연성, 내후성이 우수하고, 85%의 투과율을 보이는 특성에 의하여 Flexible display의 기판으로 많은 연구가 진행되고 있다. 이와 같은 PET film에 ITO를 증착하여 광 투과도와 전기전도도가 우수한 Flexible display의 투명전극으로 많은 연구 개발이 이루어지고 있다. Flexible ITO 박막의 특성을 향상하기 위해서는 $200^{\circ}C$ 이상의 열처리 공정이 필요하지만, PET는 약 $200^{\circ}C$ 이상에서 열 변형이 일어나므로 열처리 공정이 어렵고 이러한 문제점을 해결하기 위해 ITO/PET film에서 PET film의 변형 없이 ITO 박막의 표면에 전자빔 형태로 조사하여 박막의 물성을 개선하는 연구가 진행되고 있다 [1]. 본 연구에서는 ITO/$SiO_2$가 증착된 PET film에 전자빔을 조사하여 ITO 박막의 물성 변화를 관찰하였고, 전자빔 에너지 변화 및 전자빔 조사 시간에 따라 ITO film의 전기적, 광학적 특성 변화를 분석하였다. 구조적 특성은 XRD (X-ray diffraction), 전기적 특성은 4-point probe, Hall measurement를 이용하였으며, 가시광영역의 광 투과도는 UV-Vis spectrometer로 측정하였다. 전기 광학적 특성 변화는 Figure of Merit (FOM) 수치로 분석하였다. 이 실험으로 PET film에 직접적인 열을 가하지 않으면서 ITO 박막의 표면에 전자빔을 조사 하여, 박막의 전기전도도 및 광 투과율, 결정성 향상 등을 관찰할 수 있었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.425-425
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• 2008

The transparent conducting oxides(TCOs) are widely used as electrodes for most flat panel display devices(FPDs), electrodes in solar cells and organic light emitting diodes(OLED). Among them, indium oxide materials are mostly used due to its high electrical conductivity and a high transmittance in the visible spectrum. The present study reports on a study of the electrical and optical properties of IGZO thin films prepared on glass and PET substrates by the combinational magnetron sputtering. We use the targets of IZO and Ga2O3 for the deposition process. In some case the deposition process is coupled with the End-Hall ion-beam treatment onto the substrates before the sputtering. In addition we control the deposition rate to optimize the film quality and to minimize the surface roughness. Then we investigate the effects of the Ar gas pressure and RF power during the sputtering process upon the electrical, optical and morphological properties of thin films. The properties of prepared IGZO thin films have been analyzed by using the XRD, AFM, a-step, 4-point probe, and UV spectrophotometer.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.1
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• pp.11-16
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• 2016

The conduction behavior and electron concentration change in a-IGZO thin-films according to the RTA (rapid thermal annealing) were studied. The electrical characteristics of TFTs (thin-film-transistors) annealed by different temperatures were measured. The sheet resistance, electron concentration, and oxygen vacancy of a-IGZO film were measured by the four-point-probe-measurement, hall-effect-measurement, and XPS analysis. The RTA process increased the driving current of IGZO TFTs but the VTH shifted to the negative direction at the same time. When the RTA temperature is higher than $250^{\circ}C$, the leakage current at off-state increased significantly. This is attributed to the increase of oxygen vacancy resulting in the increase of electron concentration. We demonstrate that the RTA is a promising process to adjust the VTH of TFT because the RTA process can easily modify the electron concentration and control the conductivity of IGZO film with short process time.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.3
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• pp.194-197
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• 2013

We investigated the effect of etching time on the surface roughness, and electrical and optical properties of ZnO and 2 wt% Al-doped ZnO (AZO) films. The ZnO and AZO films were deposited on glass substrates by RF magnetron sputtering technique. The etching experiment was carried out using a solution of 5% HCl at room temperature. The surface roughness was characterized by Atomic Force Microscopy. The electrical property was measured by Hall measurement system and 4-point probe. The optical property was characterized by UV-vis spectroscopy. After the wet chemical etching, the surface textures were obtained on the surface of the ZnO and AZO films. With the increase of etching time, the surface roughness (RMS) of the films increased and the transmittance of the films was observed to decrease. For the AZO film, a low resistivity of $1.0{\times}10^{-3}\;{\Omega}{\cdot}cm$ was achieved even after the etching.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.412-413
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• 2007

We report on the electrical, optical, and structural properties of indium zinc tin oxide (IZTO) anode films grown at room temperature on glass substrate. The IZTO anode films grown by a RF magnetron sputtering were investigated as functions of RF power, working pressure, and process time in pure Ar ambient. To investigate electrical, optical and structural properties of IZTO anode films, 4-point probe, Hall measurement, UV/Vis spectrometer, Field Emission Scanning Electron Microscopy (FE-SEM), and X-ray diffraction (XRD) were performed, respectively. A sheet resistance of $13.88\;{\Omega}/{\square}$, average transmittance above 80 % in visible range were obtained from optimized IZTO anode films grown on glass substrate. These results shown the amorphous structure regardless of RF power and working pressure due to low substrate temperature.

• Journal of the Korean Vacuum Society
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• v.9 no.1
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• pp.30-35
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• 2000

Indium-Tin Oxide (ITO) thin films were deposited on the commercial glass substrate by rf-magnetron sputtering. The ITO films with the thickness of 2,000~2,400 $\AA$ were prepared by changing the oxygen partial pressures of 2, 3, and 5%, as well as by changing the substrate temperature of $300^{\circ}C$ and $500^{\circ}C$. spectrophotometer, XRD, SEM, AFM, 4-point probe and Hall effect system were employed to characterize the ITO films. The optimum deposition conditions were the substrate temperature of $500^{\circ}C$ and oxygen partial pressure of 2-3%. At theses conditions, the ITO film showed the transmittance of 91%, the resistivity of $5.4\times10^{-3}\Omega$cm, the carrier concentration of $1.0\times10^{19}\textrm{cm}^{-3}$, and the carrier mobility of 150$\textrm{cm}^2$/Vsec. In XRD spectra, the (222) and (400) $In_2O_3$ planes were dominant under the optimum deposition conditions When the substrate was cleaned only by the method of ultrasonic cleaning without both pre-annealing and chemical treatment of the substrate, the ITO film exhibited the transmittance of 86%, the carrier concentration of $5.4\times10^{19}\textrm{cm}^{-3}$ and the mobility of 24$\textrm{cm}^2$/Vsec.