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[주간세미나] 2015년 10월 12일
관리자 2015-10-07

<이내응교수 Lab.>

* 발표자 : 김진수

* 제목 : Fabrication of organic/inorganic hybrid gate insulator materials and low strain back plane structure based on OTFTs

* 내용 : Organic gate dielectric layers in thin film transistors (TFTs) of backplane for flexible displays have been developed because of their superior flexibility. However, organic materials have several disadvantages like low thermal and chemical resistivity. Furthermore, organic insulators have low dielectric constant leads to high threshold voltage of TFTs, which also occurs high power consumption. On the other hands, although inorganic gate dielectrics have high dielectric constant and low leakage current characteristics, they can be easily cracked under mechanical deformation. In order to maintain flexibility and high dielectric constant, therefore, it is essential to develop the hybrid insulator based on organic and inorganic materials. In this respect, we have fabricated organic/inorganic nanocomposite gate insulators using self-assembled monolayers (SAMs) of nanoparticles (NPs) and integrated them into flexible TFTs. To manufacture the nanocomposite gate insulators, polyimide (PI) was chosen as the organic material due to their high flexibility and good thermal stability. ZrO2 and HfO2 NPs explored as inorganic materials for nanocomposite gate insulators. In order to improve the characteristics of gate dielectric layers, we manufactured nano hybrid laminated structure using 20nm-thickness Al2O3 by atomic layer deposition (ALD). To analyze gate dielectric properties such as the capacitance, and leakage current characteristic, metal-insulator-metal (MIM) structures were prepared. The electrical characteristics of nanocompsoite gate insulators after cyclic bending of 100,000 times indicated the improved mechanical stability of nanocomposite gate dielectrics. In addition, good thermal stability of nanocomposite gate insulators at 350 for 1 hour was obtained, which indicates the possibility of improving the thermal and electrical properties of nanocomposite insulators.

* 발표자 : Saqib Siddiqu

* 제목 : Biomechanical Energy Harvesting using Lead Free Piezoelectric Nanogenerator

* 내용 : Developing renewable and sustainable power sources is a requisite for the smooth and cost effective operations of autonomous micro/nano systems, wearable electronics, and implantable biomedical devices. In this scenario piezoelectric nanogenerator (PENG) shows a great potential, having the capability of converting ambient mechanical vibrations into electricity. In this work we demonstrate a flexible, lead-free, solution-processable and efficient thin film PENG based on a barium titanate nanoparticles (BT NPs) embedded into a highly crystalline polyvinylidene fluoride&8211tri&64258uoroethylene (PVDF-TrFE) polymer matrix. The nanocomposite PENG (nc-PENG) can efficiently harvest energy from simple body motion which can fully charge a rechargeable micro-battery (12 µAh) with in few minutes. The nanocomposite PENG (nc-PENG) can generate open circuit voltage as high as 9.8 V and a power density of 13.5 µW/cm2 under cyclic bending with 40wt% loading of BT NPs, comparable to the output of conventional inorganic polycrystalline PZT PENGs. High performance and flexibility are mainly attributed to the highly crystalline piezoelectric matrix embedded with uniformly dispersed BT NPs. The nc-PENG shows great output stability even after 5000 vigorous bending cycles without any significant in performance. Furthermore the demonstrated nc-PENG provides feasibility for self-powered implantable devices for biomedical applications without any passivation layers due to no lead content.
[주간세미나] 2015년 10월 5일
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