• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.191-191
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• 2008

강유전성 세라믹스 재료로써는 PZT계열의 세라믹재료가 널리 쓰이고 있다. 이는 우수한 유전 및 압전특성을 가지고 있으나, PbO을 다량 함유하고 있어 $1000^{\circ}C$이상에서 PbO가 급격하게 휘발되는 성질 때문에 조성의 변동이 생겨 재현성이 어려우며 이를 방지하기 위하여 PbO를 과잉 첨가시키기 때문에 PbO휘발로 인한 강한 독성이 인체에 유해하고, 비환경 친화적인 물질로 최근에는 환경문제가 대두됨에 따라 대체 또는 보완 할 수 있는 방안에 검토되고 있다. 본 연구는 그 해결책의 한 방안으로 압전특성이 우수한 $(Pb_{0.94}Sr_{0.06})[(Ni_{1/2}W_{1/2})_{0.02}(Mn_{1/3}Nb_{2/3})_{0.07}(Zr_{0.51}Ti_{0.49})_{0.91}]O_3$계 조성을 설계하고 Glass frit(0~1.1 wt%)를 소량 첨가하여 액상 소결 특성을 부여하고 $1000^{\circ}C$ 이하의 저온에서 소결하여 유전 및 압전 특성을 평가하였다. 실험방법은 일반적인 세라믹스 제조공정으로 24시간 ball milling하고 $850^{\circ}C$에서 2시간 하소 후 Glass frit를 소결조제로 소랑 첨가하여 $1000^{\circ}C$ 이하 온도에서 소결을 진행하여 각 소결온도에 따른 유전 및 압전 특성을 평가하였다. 최종 소결된 시편의 밀도와 수축율을 분석하여 최적의 소결온도를 확립하였으며 XRD분석을 통해 perovskite구조를 확인하고 미세구조확인을 위해 SEM으로 관찰하였다. 압전 특성을 평가하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.108-108
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• 2007

Inkjet printing is a non-contact and direct writing associated with a computer. In the industrial field, there have been many efforts to utilize the inkjet printing as a new way of manufacturing, especially for electronic devices. The etching resist used in this process is an organic polymer which becomes solidified when exposed to ultraviolet lights and has high viscosity of 300 cPs at ambient temperature. A piezoelectric-driven ink jet printhead is used to dispense $20-40\;{\mu}m$ diameter droplets onto the copper substrate to prevent subsequent etching. In this study, factors affecting the pattern formation such as printing resolution, jetting property, adhesion strength, etching and strip mechanism, UV pinning energy have been investigated. As a result, microscale Etch resist patterning of printed circuit board with tens of ${\mu}m$ high have been fabricated.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.115-116
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• 2012

The demand for flexible electronic systems such as wearable computers, E-paper, and flexible displays has increased due to their advantages of excellent portability, conformal contact with curved surfaces, light weight, and human friendly interfaces over present rigid electronic systems. This seminar introduces three recent progresses that can extend the application of high performance flexible inorganic electronics. The first part of this seminar will introduce a RRAM with a one transistor-one memristor (1T-1M) arrays on flexible substrates. Flexible memory is an essential part of electronics for data processing, storage, and radio frequency (RF) communication and thus a key element to realize such flexible electronic systems. Although several emerging memory technologies, including resistive switching memory, have been proposed, the cell-to-cell interference issue has to be overcome for flexible and high performance nonvolatile memory applications. The cell-to-cell interference between neighbouring memory cells occurs due to leakage current paths through adjacent low resistance state cells and induces not only unnecessary power consumption but also a misreading problem, a fatal obstacle in memory operation. To fabricate a fully functional flexible memory and prevent these unwanted effects, we integrated high performance flexible single crystal silicon transistors with an amorphous titanium oxide (a-TiO2) based memristor to control the logic state of memory. The $8{\times}8$ NOR type 1T-1M RRAM demonstrated the first random access memory operation on flexible substrates by controlling each memory unit cell independently. The second part of the seminar will discuss the flexible GaN LED on LCP substrates for implantable biosensor. Inorganic III-V light emitting diodes (LEDs) have superior characteristics, such as long-term stability, high efficiency, and strong brightness compared to conventional incandescent lamps and OLED. However, due to the brittle property of bulk inorganic semiconductor materials, III-V LED limits its applications in the field of high performance flexible electronics. This seminar introduces the first flexible and implantable GaN LED on plastic substrates that is transferred from bulk GaN on Si substrates. The superb properties of the flexible GaN thin film in terms of its wide band gap and high efficiency enable the dramatic extension of not only consumer electronic applications but also the biosensing scale. The flexible white LEDs are demonstrated for the feasibility of using a white light source for future flexible BLU devices. Finally a water-resist and a biocompatible PTFE-coated flexible LED biosensor can detect PSA at a detection limit of 1 ng/mL. These results show that the nitride-based flexible LED can be used as the future flexible display technology and a type of implantable LED biosensor for a therapy tool. The final part of this seminar will introduce a highly efficient and printable BaTiO3 thin film nanogenerator on plastic substrates. Energy harvesting technologies converting external biomechanical energy sources (such as heart beat, blood flow, muscle stretching and animal movements) into electrical energy is recently a highly demanding issue in the materials science community. Herein, we describe procedure suitable for generating and printing a lead-free microstructured BaTiO3 thin film nanogenerator on plastic substrates to overcome limitations appeared in conventional flexible ferroelectric devices. Flexible BaTiO3 thin film nanogenerator was fabricated and the piezoelectric properties and mechanically stability of ferroelectric devices were characterized. From the results, we demonstrate the highly efficient and stable performance of BaTiO3 thin film nanogenerator.