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Characteristics of a NOx Gas Sensor based on a Low-Temperature Co-Fired Ceramic and Ga-Doped ZnO
송준태,Hyun-Suk Hwang,여동훈,신효순,홍연우,김종희,임동건 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.3
For certain applications, the small-size characteristics of MEMS structures can be traded off for low cost production and high manufacturing yields. Low-temperature co-fired ceramic (LTCC) is a more promising material for this application than a silicon substrate. In this work, Ga-doped ZnO (GZO) thin films for gas-sensor applications were deposited on LTCC substrates by using a RF magnetron sputtering method. The LTCC substrates with thicknesses of 400 μm were fabricated by laminating 12 green tapes consisting of alumina and glass particles in an organic binder. The microstructures of the GZO thin films were analyzed by using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The films were well crystallized in the hexagonal (wurzite) structure and the sensors showed good sensitivity for the NOx gas at a lower operating temperature.
송준태,Hyun-Suk Hwang 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.3
The dielectric characteristics of in-plane-polarized feroelectric transducers are analyzed and an equivalent model is suggested. The geometric configuration of feroelectric transducers with interdigitated electrodes (IDE) is symmetricaly simplified and the electric field distribution is analyzed using the finite-element method (FEM). The FEM result shows that the field distribution of the inner feroelectric film between the electrodes is uniform in the in-plane direction and that the eects of the fields in the air and in the inner feroelectric film under the electrodes are negligible. A simplified in-plane equivalent model is derived from the results and the effectiveness of the model is verified by comparing a capacitance value calculated using the model with a simulated result from the FEM analysis and a computation of the energy of the system. The capacitance values are 1.66 and 1.61 pF, respectively. The dielectric characteristics of the fabricated in-plane-polarized lead-zirconate-titanate (PZT) transducers are also tested. The calculated result (3.42 nF) is close to the measured value (3.27 nF).
PVDF 필름을 이용한 효과적인 에너지 하베스팅에 관한 연구
허원영,이태용,이경천,황현석,송준태,Hur, Won-Young,Lee, Tae-Yong,Lee, Kyung-Chun,Hwang, Hyun-Suk,Song, Joon-Tae 한국전기전자재료학회 2011 전기전자재료학회논문지 Vol.24 No.5
Piezoelectric materials can be used to convert mechanical energy into electrical energy. In this study, we investigated the possibility of harvesting from mechanical vibration force using a high efficient piezoelectric material-polyvinylidene fluoride (PVDF). A piezoelectric energy harvesting system consists of rectifier, filter capacitor, resistance. The experiments were carried out with impacting force to PVDF film with the thickness of 1 ${\mu}m$. The output power was measured with change in the load resistance value from 100 ${\Omega}$ to 2.2 $M{\Omega}$. The highest power was obtained under optimization by selection of suitable resistive load and capacitance. A power of 0.3082 ${\mu}W/mm^2$ was generated at the external vibration force of 5 N (10 Hz) across a 1 $M{\Omega}$ optimal resistor. Also, the maximum power of 0.345 ${\mu}W/mm^2$ was generated at 22 ${\mu}F$ and 1 $M{\Omega}$. The developed system was expected at a solution to overcome the critical problem of making up small size energy harvester.
황현석,여동훈,김종희,송준태,Hwang, Hyun-Suk,Yeo, Dong-Hun,Kim, Jong-Hee,Song, Joon-Tae 한국전기전자재료학회 2008 전기전자재료학회논문지 Vol.21 No.6
In this work, Ga-doped ZnO (GZO) thin films for gas sensor application were deposited on low temperature co-fired ceramics (LTCC) substrates, by RF magnetron sputtering method. The LTCC substrate is one of promising materials for this application since it has many advantages (e.g., low cost production, high manufacturing yields and easy realizing 3D structure etc.). The LTCC substrates with thickness of $400\;{\mu}m$ were fabricated by laminating 12 green tapes which consist of alumina and glass particle in an organic binder. The structural properties of the fabricated GZO thin film with thickness of 50 nm is analyzed by X-ray diffraction method (XRD) and field emission scanning electron microscope (FESEM). The film shows good adhesion to the substrate. The GZO gas sensors are tested by gas measurement system and show fast response and recovery characteristics to $NO_x$ gas that is 27.2 and 27.9 sec, recpectively.
저온동시소성세라믹 기판 위에 제작된 PZT 박막의 증착조건이 박막의 구조적 특성에 미치는 영향
이경천,황현석,이태용,허원영,송준태,Lee, Kyung-Chun,Hwang, Hyun-Suk,Lee, Tae-Yong,Hur, Won-Young,Song, Joon-Tae 한국전기전자재료학회 2011 전기전자재료학회논문지 Vol.24 No.4
Recently, low temperature co-fired ceramic (LTCC) technology is widely used in sensors, actuators and microsystems fields because of its very good electrical and mechanical properties, high reliability and stability as well as possibility of making 3D micro structures. In this study, we investigated the effects of sputtering gas ratio and annealing temperature on the crystal structure of $Pb(ZrTi)O_3$ (PZT) thin films deposited on LTCC substrate. The LTCC substrate with thickness of $400\;{\mu}m$ were fabricated by laminating 4 green tapes which consist of alumina and glass particle in an organic binder. The PZT thin films were deposited on Pt / Ti / LTCC substrates by RF magnetron sputtering method. The results showed that the crystallization of the films were enhanced as increasing $O_2$ mixing ratio. At about 25% $O_2$ mixing ratio, was well crystallized in the perovskite structure. PZT thin films was annealed at various temperatures. When the annealing temperature is lower, the PZT thin films become a phyrochlore phase. However, when the annealing temperature is higher than $600^{\circ}C$, the PZT thin films become a perovskite phase. At the annealing temperature of $700^{\circ}C$, perovskite PZT thin films with good quality structure was obtained.