• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 춘계학술대회 논문집
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• pp.139-142
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• 1998

PLZT thin films were fabricated with different Zr/Ti ratios by pulsed laser deposition. PLZT films deposited on Pt/Ti/SiO$_2$/Si substrate. This PLZT thin films of 5000${\AA}$. thickness were crystallized at 600$^{\circ}C$, 200 mTorr O$_2$ press. 2/55/45 PLZT thin film showed a maximum dielectric constant value of $\varepsilon$$\_$r/=1500, and dielectric loss was 0.O$_3$. At 2/70/30 PLZT thin film, Coercive field and remnant polarization was respectively 19[kV/cm], 8[${\mu}$C/$\textrm{cm}^2$].

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.82-82
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• 1999

Ferroelectric materials are characterized by the existence of a spontaneous remnant polarization that can be switched between two stable states by an applied field. This phenomenon is known as ferroelectricity. The ferroelectricity can be utilized for nonvolatile memory application. Up to now 256K FRAM was successfully fabricated and sold in the memory market. This paper will briefly review the current statue of ferroelectric random access memory (FRAM) focusing on recent developments. In addition, the future prospects of FRAM will be addressed.

• E2M - 전기 전자와 첨단 소재
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• 제7권5호
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• pp.369-375
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• 1994

In this study, ferroelectric thin films of PZT with different Zr/Ti ratio were prepared by sol-get processing and annealed by rapid thermal annealing at >$500^{\circ}C$>$-700^{\circ}C$ for 10 sec. -1 min. Structures of the annealed films were examined by X-ray diffraction and SEM. Thin films of PZT with perovskite structure have been obtained by annealing at >$600^{\circ}C$ or above and for 20 seconds or longer. Maximum remnant polarization of 10.24.mu.C/cm$^{2}$ and minimum coercive field of 20.06 kV/cm were obtained from the 56/44 and 65/35 Zr/Ti composition films, respectively. Dielectric constant, .epsilon.$_{r}$ of 500-1300 and dielectric loss, tan .delta., of 0.01-0.035 were obtained from the films.s.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.1106-1109
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• 1993

Ferroelectric thin films of PZT with differnt Zr/Ti ratio were prepared by sol-gel processing and annealed by rapid-thermal-annealing at $500^{\circ}C-700^{\circ}C$ for 10sec-1min. The structure of the annealed films were examined by X-ray diffraction and SEM. Maximum remnant polarization of 10.24 ${\mu}m/cm^2$ and coercive field of 70 KV/cm were obtained from hysteresis curve or the film.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 춘계학술발표강연 및 논문개요집
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• pp.34-34
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• 2003

Piezoelectric or magnetostrictive materials, known as smart materials, have been researched widely for sensors or actuators in micro system technology. In our research, thick sol-gel lead zirconate titanate(Pb(Zr$\sub$1-x/Ti$\sub$x/)O$_3$) films were fabricated and their characteristics were investigated f3r angular rate sensor applications. The thickness of the PZT films is 1.5${\mu}$m, which is required by a vibration angular rate sensor for a good actuation and sensing. The remnant polarization of the PZT flms is 12.0 ${\mu}$C/$\textrm{cm}^2$. The electromechanical constants of PZT thin film showed the value of susceptance(B) of 4800${\mu}$ s at capacitance of 790pF. The PZT films were applied to the vibration angular rate sensor structure and the vibration of 1.78 ${\mu}$m in amplitude at the resonant frequency of 35.8㎑ was obtained by driving voltage of 5V$\sub$p-p/ of bulk piezoelectric materials with out of phase signal through voltage and inverting amplifier.

• 한국전기전자재료학회논문지
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• 제13권3호
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• pp.214-219
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• 2000

In this paper the structural dielectric and piezoelectric properties of Pb［(M $g_{1}$2// $W_{1}$2/)$_{x}$-(N $i_{1}$3//N $b_{2}$3/)$_{0.15-x-(Zr_{0.5})}$ $Ti_{0.5}$)$_{0.85}$］ $O_3$ (x=0.0~0.10) ceramic were investigated with the substitution of Pb(M $g_{1}$2// $W_{1}$2/) $O_3$. According to the substitution of Pb(M $g_{1}$2//W/1/2/) $O_3$ curie temperatures were slightly decrease due to the decrease of the tetrag-onality of crystal structure and coercive fields were decreased. Up to the substitution of Pb(M $g_{1}$2// $W_{1}$2/) $O_3$ 3mol%,remnant polarization dielectric constant piezoelectric constant were increased. Dielectric constant and electro-mechanical coupling factor( $k_{p}$, $k_{31}$ ) were appeared the highest value of 2230, 0.64, and 0.38 and piezoelectric constant( $d_{33}$ , $d_{31}$ ) was the largest value of 418, 202($\times$10$^{-12}$ /C/N), respectively, when the substitution amount of Pb(M $g_{1}$2// $W_{1}$2/N) respectively, when the substitution amount of Pb(M $g_{1}$2// $W_{1}$2/) $O_3$ was 3mol%.s 3mol%.%.

• 한국세라믹학회지
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• 제40권2호
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• pp.206-211
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• 2003

Sol-gel 공정으로 제조된 YMnO$_3$박막의 결정상과 강유전특성에 미치는 기판종류와 버퍼층의 영향에 대하여 고찰하였다. Si(1OO) 기판위에는 hexagonal YMnO$_3$이 형성되었으나 Pt(111)/TiO$_2$/SiO$_2$/Si 기판위에는 hexagonal과 orthorhombic YMnO$_3$이 함께 형성되었다. 기판위에 미리 $Y_2$O$_3$버퍼층을 형성시킨 경우에는 Si(100)와 Pt(111)/TiO$_2$/SiO$_2$/Si 두가지 기판 모두 단일 hexagonal YMnO$_3$이 성장하였으며, 특히 c-축 배향성이 향상되었다. 박막내에 hexagonal과 orthorhombic YMnO$_3$이 혼재된 시편보다는 hexagonal 단일상이 형성된 시편이, 또한 단일상 시편중에서도 c-축 우선배향성이 좋은 시편이 그렇지 않은 시편에 비해 누설전류밀도 특성이 우수하였다. YMnO$_3$박막의 잔류분극값은 Si(100)기판을 사용했을 경우, 버퍼층 없이 제조된 시편은 0.14, 버퍼층이 삽입된 시편은 0.24$\mu$C/$ extrm{cm}^2$의 값을 나타내었다 한편 Pt(111)/TiO$_2$/SiO$_2$/Si 기판의 경우, 버퍼층 없이 형성된 YMnO$_3$시편은 이력곡선을 보여주지 못하였고, 버퍼층이 삽입된 시편은 1.14$\mu$C/$\textrm{cm}^2$의 잔류분극값을 나타내었다. 이상의 연구를 통하여 기판의 종류와 $Y_2$O$_3$버퍼층 삽입으로 YMnO$_3$박막의 결정상과 배향성을 제어함으로서 박막시편의 누설전류밀도 특성 및 강유전특성을 제어할 수 있음을 확인하였다.

• 한국재료학회지
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• 제12권12호
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• pp.962-966
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• 2002

The $SrBi_2$$Nb_2$$O_{9}$ (SBN) thin films were deposited with $SrNb_2$$O_{6}$ / (SNO) and $Bi_2$$O_3$ targets by co-sputtering method. For the growth of SBN thin films, we adopted the various power ratios of two targets; the power ratios of the SNO target to $Bi_2$$O_3$ target were 100 W : 20 W, 100 W : 25 W, and 100 W : 30 W during sputtering the SBN films. We found that the electrical properties of SBN films were greatly dependent on Bi content in films. The $Bi_2$Pt and $Bi_2$$O_3$ phase as second phases occurred at the films with excess Bi content greater than 2.4, resulting in poor ferroelectric properties. The best growth condition of the SBN films was obtained at the power ratio of 100 W : 25 W for the two targets. At this condition, the crystallinity and electrical properties of the films were improved at even low annealing temperature as $700^{\circ}C$ for 1h in oxygen ambient and the Sr, Bi and Nb component in the SBN films were about 0.9, 2.4, and 1.8 respectively. From the P-E and I-V curves for the specimen, the remnant polarization value ($2P_{r}$) of the SBN films was obtained about 6 $\mu$C/c $m^2$ at 250 kV/cm and the leakage current density of this thin film was $2.45$\times$10^{-7}$ $A/cm^2$ at an applied voltage of 3 V.V.

• Smart Structures and Systems
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• 제12권1호
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• pp.55-71
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• 2013

Structural health monitoring (SHM) is vital for detecting the onset of damage and for preventing catastrophic failure of civil infrastructure systems. In particular, piezoelectric transducers have the ability to excite and actively interrogate structures (e.g., using surface waves) while measuring their response for sensing and damage detection. In fact, piezoelectric transducers such as lead zirconate titanate (PZT) and poly(vinylidene fluoride) (PVDF) have been used for various laboratory/field tests and possess significant advantages as compared to visual inspection and vibration-based methods, to name a few. However, PZTs are inherently brittle, and PVDF films do not possess high piezoelectricity, thereby limiting each of these devices to certain specific applications. The objective of this study is to design, characterize, and validate piezoelectric nanocomposites consisting of zinc oxide (ZnO) nanoparticles assembled in a PVDF copolymer matrix for sensing and SHM applications. These films provide greater mechanical flexibility as compared to PZTs, yet possess enhanced piezoelectricity as compared to pristine PVDF copolymers. This study started with spin coating dispersed ZnO- and PVDF-TrFE-based solutions to fabricate the piezoelectric nanocomposites. The concentration of ZnO nanoparticles was varied from 0 to 20 wt.% (in 5 % increments) to determine their influence on bulk film piezoelectricity. Second, their electric polarization responses were obtained for quantifying thin film remnant polarization, which is directly correlated to piezoelectricity. Based on these results, the films were poled (at 50 $MV-m^{-1}$) to permanently align their electrical domains and to enhance their bulk film piezoelectricity. Then, a series of hammer impact tests were conducted, and the voltage generated by poled ZnO-based thin films was compared to commercially poled PVDF copolymer thin films. The hammer impact tests showed comparable results between the prototype and commercial samples, and increasing ZnO content provided enhanced piezoelectric performance. Lastly, the films were further validated for sensing using different energy levels of hammer impact, different distances between the impact locations and the film electrodes, and cantilever free vibration testing for dynamic strain sensing.

• 한국결정성장학회지
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• 제25권6호
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• pp.239-244
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• 2015

에어로졸 증착법에 의해 실리콘 기판위에 $10{\sim}20{\mu}m$의 두께를 가진 PZT 후막을 제조한 후 $700^{\circ}C$에서 어닐링처리하였다. PZT 분말에 의해 제조된 막은 임피던스 분석기(impedance analyzer)와 쇼여-타워 서킷(Sawyer-Tower circuit)으로 분석하였다. PZT 분말은 통상적인 고상반응법 및 솔-젤 법으로 준비되었다. 고상반응법으로 만들어진 분말을 사용한 $10{\mu}m$ 두께 PZT 막의 잔류분극, 항전계 및 유전상수는 각각 $20{\mu}C/cm^2$, 30 kV/cm 그리고 1320이었다. 한편 솔-젤 법으로 제조된 분말을 사용한 경우의 유전상수는 635로 비교적 낮은 값을 나타낸다. 이는 어닐링시 생기는 발생하는 유기물에 의한 기공의 존재 때문이다.