• 마이크로전자및패키징학회지
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• 제25권1호
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• pp.29-33
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• 2018

미래의 전자 기기는 접고 굽히고 둘둘 마는 등 다양한 변형에도 전기적 안정성을 가지는 기기들로 발전할 것이며, 반복 기계적 변형 하에서 유연 전자 소자의 전기적 신뢰성 확보가 중요한 이슈로 부각되고 있다. 본 연구에서는 반복 롤링 변형이 가능한 장치를 개발하고 이를 이용해, 현재 유연 전자 소자용 투명 전극 소재로 가장 널리 사용 중인 ITO 박막의 반복 롤링 실험 중 전기적 특성 변화를 연구하였다. 전극과 기판의 상대적 위치에 의해 인장 응력과 압축 응력이 가해지므로, Outer rolling 및 Inner rolling의 두 조건에서 실험을 진행하여 응력 상태에 따른 전기적 신뢰성 차이를 연구하였다. 그 결과, inner rolling의 경우 outer rolling에 비해 더 우수한 전기적 안정성을 나타냈으며, 이는 inner bending에 의한 압축 응력 상태의 경우 crack closing 변형에 따라 전기저항이 상대적으로 낮게 증가하는 것으로 해석된다. 또한, 롤링 바퀴 수에 따른 피로 저항성을 실시간 전기저항 측정을 통해 연구하였으며, 그 결과, 롤링 바퀴 수가 증가할수록 피로 파괴 영역이 증가하므로 전기저항이 더욱 크게 증가하는 것으로 나타났다. 본 연구를 통해 롤링 조건에서 유연 전극의 신뢰성에 대해 이해하고, 이는 향후 유연 전자소자용 고신뢰성 전극 개발에 활용 될 수 있을 것으로 기대한다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제17권1호
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• pp.72-77
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• 2017

Purpose: The electrochemical corrosion behavior of tin oxide film coated on PET substrates has been studied under varying concentrations of acrylic acid to investigate possible corrosion in contact with the acidic environment. Method: Potentiodynamic test was performed for a commercial ITO/PET film in 0.1, 0.3, and 0.5 M of acrylic acid. The surface morphology was analyzed by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Results: Potentiodynamic test results showed an increase in Icorr and decrease in Ecorr value with increasing concentration of acid. Microscopic evaluation suggested the presence of certain deep cracks on the surface of the film in addition with a severe acidic attack. Conclusion: Exposure of ITO to acrylic acid resulted in the stress corrosion cracking of ITO film due to the mechanical mismatch between brittle inorganic ITO fim and a compliant organic PET substrate leading to the subsequent failure of the film.

• 대한화학회지
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• 제65권2호
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• pp.125-132
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• 2021

An electrochromic nickel oxide thin film was fabricated on a flexible PET/ITO substrate using a nanocrystallite- dispersed coating sol and bar coater. Nanocrystalline NiOx of 3-4 nm crystallite size was first synthesized by base precipitation and thermal conversion. This NiOx nanocrystallite powder was mechanically dispersed in an alcoholic solvent mixed with a silane binder to prepare a coating sol for thin film. This sol method is different from the normal sol-gel method in that it does not require the conversion of precursor by heat treatment. Therefore, this method provides a very facile method to prepare NiOx thin films on any kind of substrate and it can be easily applied to mass production. The electrochromic performance of this NiOx thin film on PET/ITO electrode with a thickness of about 400 nm was investigated in a nonaqueous LiClO4 electrolyte solution by cyclic voltammetric and repeated chronoamperometric measurements in conjunction with spectrophotometry. The visible light modulation of 44% and the colorization efficiency of 41 ㎠/C at 550 nm were obtained at the step potentials of -0.8/+1.2 V vs Ag and a duration of 30 s.

• 한국표면공학회지
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• 제42권1호
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• pp.21-25
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• 2009

Using an evaporation system, $SiO_2$ was deposited as a buffer layer between a PET substrate and a ITO layer and then ITO/$SiO_2$/PET layers were annealed for 1.5 hours at the temperature of $180^{\circ}C$. Adhesion and electro-optical properties of ITO films were studied with thickness variance of a $SiO_2$ buffer layer. As a result of introduction of the $SiO_2$ buffer layer, sheet resistance and resistivity increased and a ITO film with optimum sheet resistance ($529.3{\Omega}/square$) for an upper ITO film of resistive type touch panel could be obtained when $SiO_2$ of $50{\AA}$ was deposited. And it was found that ITO films with $SiO_2$ buffer layer have higher transmittance of $88{\sim}90%$ at 550 nm wavelength than ITO films with no buffer layers and the transmittance was enhanced as $SiO_2$ thickness increased from $50{\AA}$ to $100{\AA}$. Adhesion property of ITO films with $SiO_2$ buffer layers became better than ITO films with no buffer layers and this property was independent of $SiO_2$ thickness variance ($50{\sim}100{\AA}$). By depositing a $SiO_2$ buffer layer of $50{\AA}$ on the PET substrate and sputtering a ITO thin film on the layer, a ITO film with enhanced adhesion, electro-optical properties could be obtained.

• 한국표면공학회지
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• 제42권6호
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• pp.276-279
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• 2009

ITO and ITO:Ce films were deposited by DC magnetron sputtering using an ITO ($SnO_2$: 10 wt%) and $CeO_2$ doped ITO ($CeO_2$: 0.5, 3.0, 4.0 and 6.0 wt%) ceramic targets, respectively, on unheated polyethylene terephthalate (PET) substrates. The lowest resistivity $6.7{\times}10^{-4}{\Omega}cm$ was obtained from ITO:Ce film deposited using $CeO_2$ (3.0 wt%) doped ITO target. On hte other hand, ITO:Ce (0.5wt%) film has the excellent mechanical durability which was evaluated by bending test. This result was attributed to the higher binding energy of $CeO_2$ compared to $SnO_2$ and $In_2O_3$. Therefore, $CeO_2$ atoms have a small displacement caused by the bombardment of high energy particles, and it attribute to the increase in adhesion caused by decrease in internal stress. The average transmittance of the films was more than 80% in the visible region.

• 한국재료학회지
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• 제19권1호
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• pp.1-6
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• 2009

In this study, the stress-strain response and the cracking behaviors of ITO film on a PET substrate are investigated. The cracking behaviors of ITO thin films deposited on a thermoplastic semi-crystalline polymer developed for flexible display applications was investigated by means of tensile experiments equipped with an electrical measurement apparatus and an in-situ optical microscope. Electrical resistance increased gradually in the elastic-to-plastic transition region of the stress strain curves and cracks formed. Numerous cracks were found in this region, and the increase of the resistance was linked to the cracking of ITO thin films. Upon loading, the initial cracks perpendicular to the tensile axis were observed at about 1% of the total strain. They propagated to the entire sample width as the strain increased. The spacing between the horizontal cracks is thought to be determined by the fracture strength and the thickness of the ITO film as well as by the interfacial strength between the ITO and PET. The effect of the strain rate on the cracking behavior was also investigated. The crack density increased as the strain increased. The spacing between the horizontal cracks (perpendicular to the stress axis) increased as the strain rate decreased. The increase of the crack density as the strain rate decreased can be attributed to the higher fraction of the plastic strain to the total strain at a given total strain. The higher critical strain for the onset of the increase in the resistance and the crack initiation of the ITO/PET with a thinner ITO film (300 ohms/sq.) suggests a higher strength of the thinner ITO film.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.175-175
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• 2010

Transparent conducting oxide (TCO) films are widely used as transparent conducting thin film material for application in various fields such as solar cells, optoelectronic devices, heat mirrors and gas sensors, etc. Recently the increased utilization of many transparent electrodes has accelerated the development of inexpensive TCO materials. Indium tin oxide (ITO) film is well-known for TCO materials because of its low resistivity, but there is disadvantage that it is too expensive. ZnO film is cheaper than ITO but it shows thermally poor stability. On the contrary, antimony-doped tin oxide films (ATO) are more stable than TCO films such as Al-doped zinc oxide (AZO) and ITO. Moreover, SnO2 film shows the best thermal and chemical stability, low cost and mechanical durability except the poor conductivity. However, annealing is proved to improve the conductivity of ATO film. Therefore, in this work, antimony (6 wt%) doped tin oxide films to improve the conductivity were deposited on 7059 corning glass by RF magnetron sputtering method for the application to transparent electrodes. In general, of all TCO films, glass is the most commonly selected substrate. However, for future development in flexible devices, glass is limited by its intrinsic inflexibility. In this study, we report the growth and properties of antimony doped tin oxide (ATO) films deposited on PES flexible substrate by using RF magnetron sputtering. The optimization process was performed varying the sputtering parameters, such as RF power and working pressure, and parameter effect on the structural, electrical and optical properties of the ATO films were investigated.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.1542-1545
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• 2009

For the application of flexible substrate to future display and new transparent devices, indium tin oxide (ITO) thin film was formed on polycarbonate(PC) substrate at room temperature by in-line sputter system. During the ITO sputtering, Ar and $O_2$ reaction gas were fixed at a constant value and the process pressure was varied from 3 to 7 mtorr. From the electrical and the optical properties of sputtered ITO films, the sheet resistances of as-deposited ITO films varied with a different pressure and the optical transmittances of the ITO films at visible wavelength were maintained above 85%. The results are considered to be due to the saturation of $O_2$ atoms from reaction in ITO film.

• 마이크로전자및패키징학회지
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• 제21권2호
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• pp.1-11
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• 2014

Flexible transparent conductive electrodes (TCEs) have recently attracted a great deal of attention owing to rapid advances in flexible electronic devices, such as flexible displays, flexible photovoltanics, and e-papers. As the performance and reliability of flexible electronics are critically affected by the quality of TCE films, it is imperative to develop TCE films with low resistivity and high transparency as well as high flexibility. Indium tin oxide (ITO) has been the most dominant transparent conducting material due to its high optical transparency and electrical conductivity. However, ITO is susceptible to cracking and delamination when it is bent or deformed. Therefore, various types of flexible TCEs, such as carbon nanotube, conducting polymers, graphene, metal mesh, Ag nanowires (NWs), and metal mesh have been extensively investigated. Among several options to replace ITO film, Ag NWs and metal mesh have been suggested as the promising candidate for flexible TCEs. In this paper, we focused on Ag NWs and metal mesh, and summarized the current development status of Ag NWs and metal mesh. The several critical issues such as high contact resistance and haze are discussed, and newly developed technologies to resolve these issues are also presented. In particular, the flexibility and durability of Ag NWs and metal mesh was compared with ITO electrode.

• 반도체디스플레이기술학회지
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• 제4권4호
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• pp.5-8
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• 2005

In this study, we prepared the ITO thin film for TOLED(Top-emitting OLED) or flexible display at room temperature using the FTS(Facing Targets Sputtering Apparatus). We observed characteristics of deposited thin films as a function of sputtering conditions. XRD patterns were independence trom oxygen gas flow and input current. But electrical and optical properties were strongly dependence. In the results, we could prepare good properties of ITO thin films resistivity of $4.27X10^{-4}[\Omega-cm]$, transmittance of over 80% at working gas pressure 1[mTorr], input current 0.6[A], oxygen gas ratio 0.3[sccm], at room temperature.