Jinnil Choi

Effect of plasma treatment on the gas sensor with single-walled carbon nanotube paste.

The effect of plasma treatment on the gas sensing properties of screen-printed single-walled carbon nanotube (SWCNT) pastes is reported. The gas sensors, using SWCNT pastes as a sensing material, were fabricated by photolithography and screen printing. The SWCNT pastes were deposited between interdigitated electrodes on heater membrane by screen printing. In order to functionalize the pastes, they were plasma treated using several gases which produce defects caused by reactive ion etching. The Ar and O(2) plasma-treated SWCNT pastes exhibited a large response to NO(2) exposure and the fluorinated gas, such as CF(4) and SF(6), plasma-treated SWCNT pastes exhibited a large response to NH(3) exposure.

Carbon nanotube and conducting polymer dual-layered films fabricated by microcontact printing

We report carbon nanotube/conducting polymer dual-layered film (CPDF) electrodes fabricated by microcontact printing for flexible transparent electrodes of organic thin film transistors (OTFTs). The CPDFs show ∼1000 Ω/sq surface resistivity and ∼93% transmittance at an extremely low loading of single-walled carbon nanotubes, and can be self-aligned with a precision of 20 μm. The CPDFs are applied as the source and drain electrodes in OTFTs without any supplementary alignment process, which leads to a mobility and a current on/off ratio of approximately 0.02 cm2 V−1 s−1 and ∼104, respectively.

Hysteresis Effects by Source/Drain Interdigitated-Finger Geometry in 6,13-Bis(triisopropylsilylethynyl)pentacene Thin-Film Transistors

This work reports on the fabrication of organic thin-film transistors (OTFTs) with a solution-based 6,13-bis(triisopropylsilylethynyl)pentacene by a drop-casting method, and the determination of the electrical properties of OTFTs having different source/drain interdigitated-finger electrodes. The results show that the hysteresis in transfer characteristics of the OTFTs depends on the variation of contact fingers. These hystereses lead to changes in threshold voltage, which originates from charge trapping/detrapping at or near the organic semiconductor/dielectric interface. These related phenomena also influence the device parameters such as the field-effect mobility, the on/off current ratio, and the gate current.

Investigation on Hermeticity of Liquid Crystal Polymer Package for MEMS Based Safety Device

Abstract Liquid crystal polymer (LCP) is a thermoplastic polymer with superior mechanical and thermal properties. In addition, itscharacteristics include very low water absorption rate and possibility to apply bonding process under low temperature. In thisstudy, LCP is utilized as a packaging material for a microelectronic system (MEMS) based safety device with suggestion ofa low temperature packaging process. Highly sensitive and stable capacitive type humidity sensor is fabricated to investigatehermeticity of the packaged MEMS device.Keywords: LCP, MEMS, Capacitive type humidity sensor, Hermeticity 1. 서론 LCP(Liquid Crystal Polymer)는 열가소성 폴리머로써 우수한 열적, 기계적 특성을 보일 뿐만 아니라 매우 낮은 수분 흡수율(0.02%) 특성을 가지고 있다[1]. 또한 상대적으로 낮은 온도인 300 o C 아래에서 본딩이 가능하여 MEMS 소자의 패키징물질로써 그 중요성이 증대되고 있다[2,3]. 따라서 본 논문에서는 액정 폴리머인 LCP를 이용한 MEMS 소자의 저온 패키징 기술을 제안하였으며 높은 감도와 안정성을 갖는 정전 용량형 습도센서를 제작하여 수분 흡수에 의한 패키지된 MEMS소자의 밀폐도 변화를 측정하는데 적용하고 응용 가능성을 확인하였다. 2. 실험 방법 2.1 정전용량형 습도센서 정전 용량형 습도센서[4,5]는 수분의 흡착 및 탈착에 의해 전기적 특성이 변하는 고분자를 감습 재료로 사용하여 습도를 측정하는 소자이다. 정전 용량은 전극 사이의 거리변화, 전극에서마주보는 면적 변화, 전극 사이 유전체 유전율 변화에 따라서결정되며 센서에 수증기가 흡착되면 폴리머의 유전율이 변하게되고 이에 따라 상대습도 0~100%RH의 정전용량 변화를 얻는다. 정전 용량형 감습 재료로서 주로 쓰이는 고분자는 폴리이미드, 셀룰로오즈계 물질, 그리고 폴리메타클레이드 유도체 등이주류를 이루며 폴리이미드의 경우에는 이미드계 내의 C=O, 셀룰로오즈 물질은 친수성이 강한 히드록시기에 소수성기를 치환시켜 습도변화에 따른 용량 변화를 측정하여 응용된다. 정전용량형 습도센서에서 감습재료로 쓰이는 물질은 수분을 흡착하는성질을 가지고 있으나 물과 반응하지 않아야 하며 온도에 영향을 받지 않아야 하는 제약이 따른다. 본 연구에서 제안한 패키지 밀폐도 측정[6-8]을 위한 정전 용량형 습도센서는 MEMS 공정 기술을 통하여 감습 재료인 폴리머에 수분+ 흡착이 쉽게 되도록 상부전극에 10 µm ± 10 µm 의마이크로 메쉬를 형성하여 제작하였다. Fig. 1은 본 연구에서 제안한 LCP로 패키지된 정전 용량형습도센서의 개념도를 보여주고 있다. 마이크로 패키지에 적용하기 위해서 센서의 면적과 예상 정전 용량값은 각각 1630 µm ×

Design of a multi-walled carbon nanotubes vacuum gauge

Measurements of the variation of vacuum level inside of field emission device when electron is emitted from carbon nanotubes (CNT) by electric field were performed. Multi-walled carbon nanotubes (MWCNT) sensor packaged with a vacuum device is used to measure the degree of a vacuum until the end of the vacuum device life. It was found that the electrical properties of MWCNTs altered with the degree of a vacuum. We fabricated MWCNT sensors which were printed and pasted by the screen printer. In this article, we report the successful detection of the ionization of gases in vacuum state.

P-110: Dual-Layered Films Consisting of CNT and Conducting Polymer Fabricated by Micro-Contact Printing for Flexible Electrodes

We report a CNT/conducting polymer dual-layered films (CPDFs), which has ∼1000Ω/sq resistance and ∼93% transmittance, self-aligned with a precision of 20μm by micro-contact printing. In addition, a potential usage of the CPDFs as a transparent electrode for the application in flexible devices including organic thin film transistor (OTFT) is demonstrated.