• Journal of Advanced Marine Engineering and Technology
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• v.30 no.8
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• pp.927-933
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• 2006

The structural and electrical characteristics of PLZT thin films fabricated onto $Pt/IrO_2/Ir/Ti/SiO_2/Si$ substrates by a pulsed laser deposition were investigated to develop the high dielectric thin films for capacitor layer of semiconductor memory devices The slim region 14/50/50 PLZT thin films were fabricated by PLD and estimated the characteristics for memory application 14/50/50 PLZT thin films have crystallize into perovskite structure at the $600^{\circ}C$ deposition temperature, 200 mTorr of oxygen pressure, and 2 $J/cm^2$ of laser energy density. In this condition PLZT thin films had the dielectric constant as high as 985, storage charge density 8.17 ${\mu}C/cm^2$ and charging time 0.20 ns. Leakage current density was less than $10^{-10}A/cm^2$ up to 5 V bias voltage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.88-88
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• 2009

$BiFeO_3$(BFO), when forming a solid solution with $BaTiO_3$(BTO), shows structural transformations over the entire compositional range, which not only gives a way to increase structural stability and electrical resistivity but also applies a means to have better ferromagnetic ordering. In this respect, we have prepared and studied 0.7BFO-0.3BTO thin films on $Pt(111)/TiO_2/SiO_2/Si$ substrates by pulsed laser deposition. Various deposition parameters, such as deposition temperature and oxygen pressure, have been optimized to get better quality films. Based on the X-ray diffraction results, thin films were successfully deposited at the temperature of $600^{\circ}C$ and an oxygen partial pressure of 10mTorr. The dielectric, ferroelectric, and magnetic properties have then been characterized. It was found that the films deposited under lower oxygen pressure corresponded to lower leakage current. Magnetism measurement showed an induced ferromagnetism. The microstructures associated with. the magnetic and dielectric properties of this mixed-perovskite solid solutions were observed by transmission electron. microscopy, which revealed the existence of complicated ferroelectric domains, suggested that the weak spontaneous magnetization was closely associated with the decrease in the extent of rhombohedral distortion by a partial substitution of $BaTiO_3$ for $BiFeO_3$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.494-498
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• 2000

RuO$_2$ thin films are prepared by RF magnetron reactive sputtering and their characteristics of crystallization, microstructure, surface roughness and resistivity are studied with various $O_2$/ (Ar+O$_2$) ratios and substrate temperatures. As $O_2$/(Ar+O$_2$) ratio decreases and substrate temperature increases, the preferred growing plane of RuO$_2$ thin films are changed from (110) to (101) plane. With increase of the $O_2$/(Ar+O$_2$) ratio from 20% to 50%, the surface roughness and the resistivity of RuO$_2$ thin films increase from 2.38nm to 7.81 nm, and from 103.6 $\mu$$\Omega$-cm to 227 $\mu$$\Omega$-cm, respectively, but the deposition rate decreases from 47 nm/min to 17 nm/min. On the other hand, as the substrate temperature increases from room temperature to 500 $^{\circ}C$, resistivity decreases from 210.5 $\mu$$\Omega$-cm to 93.7 $\mu$$\Omega$-cm. RuO$_2$ thin film deposited at 300 $^{\circ}C$ shows a excellent surface roughness of 2.38 nm. As the annealing temperature increases in the range between 400 $^{\circ}C$ and 650 $^{\circ}C$, the resistivity decreases because of the improvement of crystallinity. We find that RuO$_2$ thin film deposited at 20% of $O_2$/(Ar+O$_2$) ratio and 300 t of substrate temperature shows excellent combination of surface smoothness and low resistivity so that it is well Qualified for bottom electrodes for ferroelectric thin films.

• Journal of the Korean Ceramic Society
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• v.40 no.2
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• pp.153-158
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• 2003

Self-patterning of thin films using photosensitive sol solution has advantages such as simple manufacturing process compared to photoresist/dry etching process. In this study,$La_{0.5}SR_{0.5}CoO_3$(LSCO) thin films as an electrode material for ferroelectric memories have been prepared by spin coating method using photosensitive sol solution. La-2methoxyethoxide, Sr-ethoxide, Co-2methoxyethoxide were used as starting materials. As UV exposure time to the LSCO gel thin film increased, the UV absorption peak intensity of metal${beta}$-diketonate decreased due to reduced solubility by M(metal)-O-M bond formation. Solubility difference by UV irradiation on LSCO gel thin film allows to obtain a fine patterning of thin film. The LSCO thin films annealed over$680{\circ}C$ in air showed perovskite phase and the lowest resistivity$(4{ imes}10^{-3}{Omega}cm)$ of the thin films were obtained by annealing at$740{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.40 no.12
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• pp.1189-1196
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• 2003

Ferroelectric B $i_{3.25}$L $a_{0.75}$ $Ti_3$ $O_{12}$ (BLT) solution was synthesized by sol-gel process. BLT thin films were deposited on Pt/Ti $O_2$/ $SiO_2$/Si substrates by spin-coating. In this experiments, Bi(TMHD)$_3$, La(III)2-Methoxyethoxide, and Ti(IV) i-propoxide were used as starting materials, which were dissolved in 2-Methoxyethanol. Rapid Thermal Annealing (RTA) was used to promote crystallization of BLT thin films. The thin films with RTA process were compared with those with non-RTA process on electrical properties. After RTA process, the remanent polarization value (2Pr) of BLT thin films annealed at 72$0^{\circ}C$ was 20.46 $\mu$C/$\textrm{cm}^2$ which was approximately 27% higher than that of non-RTA process at 5 V.

• Journal of the Korean Ceramic Society
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• v.41 no.1
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• pp.13-18
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• 2004

$La_{0.5}Sr_{0.5}CoO_3$ (LSCO) electrodes were prepared on ferroelectric $Sr_{0.9}Bi_{2.1}Ta_2O_9$(SBT) thin films by spin coating method using photosensitive sol-gel solution. Self-patterning technique of photosensitive sol-gel solution has advantages such as simple manufacturing process compared to photoresist/dry etching process. Lanthanum(III) 2-methoxyethoxide, Stronitium diethoxide. Cobalu(II)2-methoxyethoxide were used as starting materials for LSCO electrode. UV irradiation on LSCO thin films lead to decrease solubility by M-O-M bond formation and the solubility difference allows us to obtain self-patternine. There was little composition change of the LSCO thin films between before leaching and after leaching in 2-methoxyethanol. The lowest resistivity of LSCO thin films deposited on $SiO_2$/Si substrate was $1.1{\times}10^{-2}{\Omega}cm$ when the thin film was ennealed at $740^{\circ}C$. The values of Pr/Ps and 2Pr of LSCO/SBT/Pt capacitor on the applied voltage of 5V were 0.51, 8.89 ${\mu}C/cm^2$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.178-181
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• 2003

In this work, we etched PZT films with various additive gases ($O_2$ and Ar) in $Cl_2/CF_4$ plasmas, while mixing ratio was fixed at 8/2. After the etching, the plasma induced damages are characterized in terms of hysteresis curves, leakage current, retention properties, and switching polarization. When the electrical properties of PZT etched in $O_2$ or Ar added $Cl_2/CF_4$ were compared, the value of remanent polarization in $O_2$ added $Cl_2/CF_4$ plasma is higher than that in Ar. added plasma. The maximum etch rate of the PZT thin films was 145 nm/min for 30% Ar added $Cl_2/CF_4$ gas having mixing ratio of 8/2 and 110 nm/min for 10% $O_2$ added to that same gas mixture. In order to recover the ferroelectic properties of the PZT thin films after etching, we annealed the etched PZT thin films at $550^{\circ}C$ in an $O_2$ atmosphere for 10 min. From the hysteresis curves, leakage current, retention property and switching polarization, the reduction of the etching damage and the recovery via the annealing was turned out to be more effective when $O_2$ was added to $Cl_2/CF_4$ than Ar. X-ray diffraction (XRD) showed that the structural damage was lower when $O_2$ was added to $Cl_2/CF_4$. And the improvement in the ferroelectric properties of the annealed samples was consistent with the increased intensities of the (100) and the (200) PZT peaks.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.910-913
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• 2002

We have achieved an improved stability of an analog electro-optic effect in FLC/polymer composite films. The optimization of device depends on both the composition of the FLC/polymer mixture and the energy of UV irradiation. This device exhibits continuous gray scales and the mechanical stability against external forces.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.3
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• pp.576-581
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• 2005

In this paper. the a-Si:H TFT using ferroelectric of $SrTiO_3$ as a gate insulator is fabricated on glass. High k gate dielectric is required for on-current, threshold voltage and breakdown characteristics of TFT Dielectric characteristics of ferroelectric are superior to $SiO_2$ and $Si_3N_4$. Ferroelectric increases on-current and decreases threshold voltage of TFT and also ran improve breakdown characteristics.$SrTiO_4$ thin film is deposited by e-beam evaporation. Deposited films are annealed for 1 hour in N2 ambient at $150^{\circ}C\~600^{\circ}C$. Dielectric constant of ferroelectric is about 60-100 and breakdown field is about IMV/cm. In this paper, the TFT using ferroelectric consisted of double layer gate insulator to minimize the leakage current. a-SiN:H, a-Si:H (n-type a-Si:H) are deposited onto $SrTiO_3$ film to make MFNS(Metal/ferroelectric/a-SiN:H/a-Si:H) by PECVD. In this paper, TFR using ferroelectric has channel length of$8~20{\mu}m$ and channel width of $80~200{\mu}m$. And it shows that drain current is $3.4{\mu}A$at 20 gate voltage, $I_{on}/I_{off}$ is a ratio of $10^5\~10^8,\;and\;V_{th}$ is$4\~5\;volts$, respectively. In the case of TFT without having ferroelectric, it indicates that the drain current is $1.5{\mu}A$ at 20gate voltage and $V_{th}$ is $5\~6$ volts. If properties of the ferroelectric thin film are improved, the performance of TFT using this ferroelectric thin film can be advanced.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05b
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• pp.78-81
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• 2002

Ferroelectric thin film is a very attractive material for the tunable microwave device applications such as electronically tunable mixers, delay lines, filters and phase shifters. Thin films of $Pb_{x}Sr_{1-x}TiO3(PST)$ were fabricated onto Pt/Ti/SiO2/Si substrate by the sol-gel method. We have investigated the structural and dielectric properties of PST(50/50) thin films for tunable microwave device applications. The PST thin films show typical polycrystalline structure with a dense microstructure without secondary phase formation. Dielectric properties of PST films are strongly dependent on annealing temperature. The dielectric constants, loss and tunability of the PST (50/50) thin films were 404, 0.023 and 51.73 %, respectively.