• 한국진공학회지
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• 제8권3A호
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• pp.194-200
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• 1999

In this paper studied was the piezoelectric properties of the $\beta$-PVDF organic thin films prepared by physical vapour deposition method. The molecular orientation of organic thin films was controlled by the application of an electric field and variation of substrate temperature during the evaporation process. Optimum conditions of manufacturing $\beta$-PVDF organic thin film by physical vapor deposition method is to keep at the substrate temperature of $80^{\circ}C$, at the applied electric field of 142.8 kV/cm. The voltage output coefficient increased from 1.39 to 7.04V increasing the force moment.

• 센서학회지
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• 제6권3호
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• pp.180-187
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• 1997

We demonstrate the improvement of sensitivity and analysis of operating characteristics of the piezoelectric pressure sensor using ZnO piezoelectric thin film and FET(field effect transistor) for sensing applied pressure and transforming the pressure into electrical signals, respectively. The sensitivity of the PSFET(pressure sensitive field effect transistor) was improved by using highly-oriented ZnO film perpendicular to the substrate surface and the operating characteristics was investigated by monitoring output voltage with time in various static pressure levels.

• 센서학회지
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• 제4권4호
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• pp.75-80
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• 1995

금속 alkoxide를 출발물질로 PZT-PNN 3성분계 압전박막을 제작하여, 박막의 결정성과 전기적 특성을 평가하였다. 박막의 X-RD 분석결과 $550^{\circ}C$ 소결온도에서 결정성이 가장 양호하였다. D-E 이력곡선의 관측 결과 항전계는 28.8 kV/cm, 잔유분극은 $18.3\;{\mu}C/cm^{2}$ 이었다. 박막의 진성파괴전압은 $76.0\;{\sim}\;27.0\;MV/m$이었고, 소결온도가 상승함에 따라 특성이 저하되었다. 박막의 비유전율은 조성비에 따라 (50:40:10)은 406, (50:30:20)은 1084, (45:35:20)은 723, (40:40:20)은 316이었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.943-946
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• 2007

In-plane piezoelectric charge constant of Electro-Active paper (EAPap) was investigated based on direct and converse piezoelectric effects. EAPap samples were made with cellulose film with very thin gold electrode coated on both sides of the film. To characterize direct piezoelectricity of EAPap, induced charge was measured when mechanical stress was applied to EAPap. In-plane piezoelectric charge constant was extracted from the relation between induced charge and applied in-plane normal stress. To investigate converse piezoelectricity, induced in-plane strain was measured when electric field was applied to EAPap. Piezoelectric charge constant was also extracted from the relation of induced in-plane strain and applied electric field. Piezoelectric charge constants obtained from direct and converse piezoelectricity are 31 pC/N and 178 x 10-12m/V for 45 degree sample, respectively. Measured piezoelectric charge constants of EAPap provide promising potential as a piezoelectric material.

• 센서학회지
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• 제27권4호
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• pp.269-274
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• 2018

High-sensitivity signal-to-noise ratio (SNR) microphones are essentially required for a broad range of automatic speech recognition applications. Piezoelectric microphones have several advantages compared to conventional capacitor microphones including high stiffness and high SNR. In this study, we designed a new piezoelectric membrane structure by using the finite elements method (FEM) and an optimization technique to improve the sensitivity of the transducer, which has a high-quality AlN piezoelectric thin film. The simulation demonstrated that the sensitivity critically depends on the inner radius of the top electrode, the outer radius of the membrane, and the thickness of the piezoelectric film in the microphone. The optimized piezoelectric transducer structure showed a much higher sensitivity than that of the conventional piezoelectric transducer structure. This study provides a visible path to realize micro-scale high-sensitivity piezoelectric microphones that have a simple manufacturing process, wide range of frequency and low DC bias voltage.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.172-175
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• 2003

ZnO:Al thin film for application to FBAR's bottom electrode using ZnO piezoelectric thin film were prepared by FTS, in order to improve the crystallographic properties of ZnO thin films because the ZnO:Al thin film and ZnO thin films structure is equal each other. So we prepared the ZnO:Al thin film with oxygen gas flow rate. Thickness and c-axis preferred orientation and electric properties of ZnO:Al bottom electrode were evaluated by $\alpha$-step, XRD and 4-point probe..

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 제5회 영호남 학술대회 논문집
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• pp.94-97
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• 2003

This study uses ZnO thin film as a piezoelectric material and Pt as bottom electrode for FBAR (film bulk acoustic resonator) device. ZnO thin film and Pt were deposited by RF-magnetron sputtering method. ZnO thin film and Pt were oriented to c-axis. Top electrode Al was deposited by thermal evaporation. The membrane was formed of bulk micromachining. The FBAR was evaluated by XRD, SEM and electrical characterization. The resonant frequency was measured by HP 8753C Network Analyzer. A fabricated FBAR device exhibited a resonant frequency of 700 MHz ~ 1.5 GHz. When bottom electrode and top electrode thickness were fixed, the resonant frequency was increased as decreasing ZnO thin film thickness.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1989년도 춘계학술대회 논문집
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• pp.66-69
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• 1989

After reviewing previous work done on two piezoelectric thin films(PZT, ZnO), ZnO thin piezofim of 1-3UM is fabricated by sputtering on the different substrates(i. e., P+Si/N-Si, SiO2/P+Si/ N-Si, Al/SiO2/ P+Si/ N+Si). The result shows that ZnO piezofilm on the Al has the best c-axis orientation. One of applications for the ZnO piezofilm as an microvalve to control liquid flow is introduced, and which can be controlled electrically and remotely.

• Journal of information and communication convergence engineering
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• 제4권3호
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• pp.111-113
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• 2006

A new thin film deposition technique of piezoelectric ZnO film and its successful application for film bulk: acoustic resonator (FBAR) devices are presented. The two-step deposition used seems to be able to deposit ZnO film with a highly preferred orientation. The FBAR devices with the ZnO films show an excellent return loss of $35{\sim}50$ dB at $1.5{\sim}2$ GHz.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.156-159
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• 2002

Film Bulk Acoustic wave Resonator (FBAR) using thin piezoelectric films can be fabricated as monolithic integrated devices with compatibility to semiconductor process, leading to small size, low cost and high Q RF circuit elements with wide applications in communications area. This paper presents a MMIC compatible Suspended FBAR using surface micromachining. It is possible to make Si$_3$N$_4$/SiO$_2$/Si$_3$N$_4$membrane by using surface micromachining and its good effect is to remove the substrate silicon loss. FBAR was made on 2$\mu\textrm{m}$ multi-layered membrane using CVD process. According to our result, Fabricated film bulk acoustic wave resonator has two adventages. First, in the respect of device Process, our Process of the resonator using surface micromachining is very simple better than that of resonator using bull micromachining. Second, because of using the multiple layer, thermal expansion coefficient is compensated, so, the stress of thin film is reduced.