• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
• /
• pp.297.2-297.2
• /
• 2013

Scavenging electricity from wasteful energy resources is currently an important issue and piezoelectric nanogenerators (NGs) based on zinc oxide (ZnO) are promising energy harvesters that can be adapted to various portable, wearable, self-powered electronic devices. Although ZnO has several advantages for NGs, the piezoelectric semiconductor material ZnO generate an intrinsic piezoelectric potential of a few volts as a result of its mechanical deformation. As grown, ZnO is usually n-type, a property that was historically ascribed to native defects. Oxygen vacancies (Vo) that work as donors exist in ZnO thin film and usually screen some parts of the piezoelectric potential. Consequently, the ZnO NGs' piezoelectric power cannot reach to its theoretical value, and thus decreasing the effect from Vo is essential. In the present study, c-axis oriented insulator-like sputtered ZnO thin films were grown in various temperatures to fabricate an optimized nanogenerator (NGs). The purity and crystalinity of ZnO were investigated with photoluminescence (PL). Moreover, by introducing a p-type polymer usually used in organic solar cell, it was discussed how piezoelectric passivation effect works in ZnO thin films having different types of defects. Prepared ZnO thin films have both Zn vacancies (accepter like) and oxygen vacancies (donor like). It generates output voltage 20 time lager than n-type dominant semiconducting ZnO thin film without p-type polymer conjugating. The enhancement is due to the internal accepter like point defects, zinc vacancies (VZn). When the more VZn concentration increases, the more chances to prevent piezoelectric potential screening effects are occurred, consequently, the output voltage is enhanced. Moreover, by passivating remained effective oxygen vacancies by p-type polymers, we demonstrated further power enhancement.

• 한국진공학회지
• /
• 제7권3호
• /
• pp.201-207
• /
• 1998

본 연구는 rf reactive magnetron sputtering 방법으로 증착한 ZnO 박막을 압전진동 자로 제작하였을 때 발생하는 금속전극과의 계면특성에 대해 조사하였다. 이때 ZnO 박막은 금속 아연 target을 산소분위기에서 sputtering하여 얻었다. 미리 얻은 최적성장조건으로 Cr/ZnO/Cr의 구조을 갖는 압전 진동자를 제작한 후, 금속전극과 ZnO 박막과의 계면특성을 분석하였다. 제작된 압전진동자는 I-V 측정, AES depth profile, SEM, C-V 측정등을 이용 하여 분석하였고, 이러한 분석 결과 금속전극과 ZnO 박막 사이에 $SiO_2$ 확산방지막을 쌓은 Cr/ $SiO_2$/ZnO/Cr의 구조로 ZnO 압전진동자를 제작했을 때 좋은 특성을 보임을 알 수 있었 다. 그리고, 이러한 사실은 제작된 진동자를 구동시키고 이에 대한 인가진동수에 따른 진동 변위를 측정해보므로써 확인할 수 있었다.

• 센서학회지
• /
• 제25권6호
• /
• pp.447-452
• /
• 2016

In this study, we fabricated and evaluated the performance of film speaker using PVDF/ZnO NP composite structure. PVDF piezoelectric films were fabricated and characterized by XRD and SEM. ZnO nanopillars were prepared by hydrothermal synthesis on prepared PVDF piezoelectric films. We analyzed and tested the acoustic signal characteristics of the piezoelectric film. In order to fabricate an acoustic structure with a wide frequency range from low to high frequency, we have fabricated various types of film speakers and investigated the frequency characteristics. As a result, the fundamental piezoelectric properties of PVDF show that the piezoelectric constant due to ZnO NP increases. And the overall acoustic signal level is also increased by 10% or more. We investigated frequency generation from 500 Hz to 10 KHz using different sizes with PVDF/ZnO NP composite film speaker.

• 한국진공학회지
• /
• 제15권6호
• /
• pp.619-623
• /
• 2006

FBAR(Film Bulk Acoustic Resonator) 소자의 공진특성을 결정하는 가장 중요한 요소는 압전막의 압전성을 들 수 있다. FBAR 압전막으로 유력한 ZnO 압전박막은 (002)면 c-축 우선배향성(preferred orientation)의 정도에 따라서 압전성이 결정된다. 그러므로 ZnO 박막의 우선배향성에 관한 연구는 많은 연구자들의 관심사가 되어왔다. 본 논문에서는 ZnO 보조씨드충(helped seed layer)을 이용하여 ZnO 압전박막의 우선배향성에 대하여 조사하였으며, rocking curve의 표준편차$(\sigma)$ 값이 $1.15^{\circ}$인 주상형 결정립을 가진 c-축 ZnO 압전박막이 우수한 압전특성을 나타내는 것을 확인하였다.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2012년도 춘계학술대회 논문집
• /
• pp.509-510
• /
• 2012

• 한국전기전자재료학회논문지
• /
• 제21권2호
• /
• pp.126-130
• /
• 2008

In this study, in order to develop low loss multilayer piezoelectric actuator, PZN-PZT ceramics were fabricated using $Li_2CO_3,\;Bi_2O_3$, CuO and ZnO as sintering aids, their structural, piezoelectric and dielectric characteristics were investigated according to the amount of ZnO addition, At the sintering temperature of $870^{\circ}C$, the density, electromechanical coupling factor(kp), mechanical quality factor(Qm), dielectric constant(${\epsilon}_r$) and piezoelectric constant($d_{33}$) of 0.4 wt% ZnO added specimen (sintered at $870^{\circ}C$) showed the optimum value of $7.812g/cm^3$, 0.535, 916, 1399, 335 pC/N respectively. Taking into consideration above piezoelectric properties of the specimen sintered at low temperature, it was concluded that PZN-PZT ceramics using 0.4 wt% ZnO as additive showed the optimum characteristics as the composition ceramics for low loss multilayer piezoelectric actuator application.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
• /
• pp.218-219
• /
• 2005

In this paper, in order to develop Pb-free piezoelectric ceramics, $[Li_{0.04}(Na_{0.44}K_{0.52})-(Nb_{0.86}Ta_{0.10}Sb_{0.04})]O_3$ ceramic was fabricated with the variation of ZnO addition. Piezoelectric properties of the ceramic were varied with the amount of ZnO addition and showed the maximum kp value at 0.2 wt% ZnO addition. Qm of ZnO added ceramics showed lower values than the non-added ceramics, however, the kp was increased by the addition of ZnO up to 0.2 wt%. At the sintering temperature of 1110$^{\circ}C$ and the calcination temperature of 850$^{\circ}C$, the optimal values of density=473g/$cm^3$, kp=0.473, $\varepsilon_r$=1403 were obtained.

• 한국전기전자재료학회논문지
• /
• 제19권8호
• /
• pp.707-711
• /
• 2006

ZnO was doped up to 0.3 wt% for improving the electrical properties of lead-free $[Li_{0.04}(Na_{0.44}Ko_{0.52})-(Nb_{0.86}\;Ta_{0.10}\;Sb_{0.04})]O_3$ piezoelectric ceramics. The ceramics were fabricated with the conventional sintering processes. Crystal structure of the samples was tetragonal phase regardless of ZnO amount. However, the piezoelectric properties were varied with the ZnO amount. The electro-mechanical coupling factor $(k_p)$ was with the ZnO amount up to 0.2 wt% but decreased with the further addition. the maximum value of $k_p$ was 0.475. Density, piezoelectric charge constant and relative dielectric constant was also showed maximum value at 0.2 wt%. The maximum values are $4.75g/cm^3$, 275 pC/N, 1403, respectively. In contrast, the mechanical quality factor $(Q_m)$ was not varied with increasing the ZnO addition up to 0.2 wt% but rapidly increased at 0.3 wt%.

• 한국전기전자재료학회논문지
• /
• 제27권11호
• /
• pp.740-745
• /
• 2014

ZnO nanowires were grown by hydrothermal synthesis process and piezoelectric poly vinylidene fluoride (PVDF) was then coated on top of the ZnO-nanowires by spray-coating technique. The composite layer of ZnO-nanowires/PVDF was applied to an energy harvesting device based on piezoelectric-conversion mechanism. A defined mechanical force was given to the nanogenerator device to evaluate their electric power generation characteristics, where output current density and voltage were examined. Electric power generation property of the ZnO-nanowires/PVDF based nanogenerator device was compared to that of the nanogenerator device with ZnO-nanowires as single active layer. Effect of the ZnO-nanowires on improvement of power generation was discussed to examine its feasibility for the nanogenerator device.

• 한국전기전자재료학회논문지
• /
• 제24권7호
• /
• pp.543-546
• /
• 2011

We studied sintering temperature to enhance the piezoelectric properties of $0.98(Na_{0.5}K_{0.5})NbO_3-0.02Li(Sb_{0.17}Ta_{0.83})O_3$+0.01wt%ZnO (hereafter NKN-LST+ZnO) lead free piezoelectric ceramics. The synthesis and sintering method were the conventional solid state reaction method and sintering was executed at $1,080\sim1,120^{\circ}C$. We found that NKN-LST+ZnO ceramics at optimal sintering temperature showed the improved piezoelectric properties at the optimal sintering temperature. The NKN-LST+ZnO ceramics show good performance with piezoelectric constant $d_{33}$= 153 pC/N sintered at $1,090^{\circ}C$. The results reveal that NKN-LST+ZnO ceramics are promising candidate materials for lead-free piezoelectric application.