• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.186.1-189
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• 2001

Ferroelectric $Bi_{4-x}$La$_{x}$Ti$_3$O$_{12}$ (BLT)thin films with various compositions(x=0.65, 0.70, 0.75) were prepared on Pt//Ti/SiO$_2$/Si(100) substrate by metal-organic deposition. The electrical and structural characteristics of BLT thin films were investigated to develop ferroelectric thin films for capacitor layers of FRAM. After spin coating, thin films were annealed at $650^{\circ}C$ for 1hour in oxygen atomosphere. Scanning electron micrographs showed uniform surfaces composed of rod-like grains. The $Bi_{4-x}$La$_{x}$Ti$_3$O$_{12}$ (x=0.70) thin film capacitors with a Pt top electrode showed better ferroelectric properties than other films. At the applied voltage of 5V, the dielectric constant($\varepsilon$$_{r}$), dissipation factor(tan$\delta$),remanent polarization(2Pr), and coercive field(2Ec) of the $Bi_{4-x}$La$_{x}$Ti$_3$O$_{12}$ (x=0.70)thin films were about 272.54, 0.059, 32.4 $\mu$C/cm$^2$, 2Ec=119.9kV/cm. Also the capacitor did not show any significant fatigue up to 4.8$\times$10$^{10}$ read/write switching cycles.hing cycles.s.

• Journal of Sensor Science and Technology
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• v.23 no.3
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• pp.170-172
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• 2014

$CO_2$ sensor was used only one solid electrolyte in many cases. To improve the sensing characteristics of $CO_2$ sensors, solid electrolyte $CO_2$ sensor has been developed by bi-electrolyte type sensor using Na-Beta-alumina and YSZ. However, in many further studies, bi-electrolyte type sensor was made by pellet pressed by press machine and additional treatment for formation of interface. In the aspect of mass production, using thick film and additional treatment is not suitable. In this study, $CO_2$ sensor was fabricated by bi-electrolyte structure which was made by an NBA paste layer deposited on YSZ pellet and fired at $1650^{\circ}C$ for 2 hour. The formation of stable interface between YSZ and NBA were confirmed by SEM image. When the type IV electrochemical cell arrangement represented by $CO_2,O_2,Pt{\mid}Li_2CO_3-CaCO_3{\parallel}NBA{\parallel}YSZ{\mid}O_2,Pt$ is used to measure the $CO_2$ concentration in air. This sensor EMF should depend only on the concentration of $CO_2$ by logarithmic. Also, sensor shows $P_{CO_2}$ and EMF relationship like nerstian reaction at a temperature of $450^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.40 no.3
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• pp.279-285
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• 2003

Ferroelectric S $r_{0.9}$B $i_{2.1}$T $a_{1.8}$N $b_{0.2}$ thin films with 200 nm thicknesses were deposited on Pt/Ti $O_2$/ $SiO_2$/Si Substrates by a sol-gel method. In these experiments, Sr(O $C_2$ $H_{5}$)$_2$, Bi(TMHD)$_3$, Ta(O $C_2$ $H_{5}$)$_{5}$ and Nb(O $C_2$ $H_{5}$)$_{5}$ were used as precursors, which were dissolved in 2-methoxyethanol. After UV-irradiation and RTA processes, the remanent polarization value (2 $P_{r}$) of SBTN thin films with annealed at $650^{\circ}C$ was 8.49 and 11.94 $\mu$C/$\textrm{cm}^2$ at 3 V and 5 V, respectively.

• Korean Journal of Materials Research
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• v.11 no.4
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• pp.290-293
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• 2001

The SrBi$_2$Nb$_2$O$_{9}$ (SBN) thin films were deposited on p-type(100) Si substrates by rf magnetron sputtering to confirm the Possibility of Pt/SBN/Si structure for the application of nondestructive read out ferroelectric random access memory (NDRO- FRAM). The SBN thin films were deposited by co-sputtering method with Sr$_2$Nb$_2$O$_{7}$ (SNO) and Bi$_2$O$_3$ ceramic targets. The SBN thin films deposited at room temperature were annealed at $700^{\circ}C$ for 1hr in $O_2$ ambient. The structural and electrical properties of SBN with different power ratios of targets were measured by x-ray diffraction(XRD), scanning electron microscopy(SEM), capacitance-voltage(C-V), and current-voltage(I-V). The C-V curves of the SBN films showed hysteresis curves of a clockwise rotation showing ferroelectricity. When the Power ratio of the SNO/Bi$_2$O$_3$ targets was 120 W/100 W, the SBN thin films had excellent electrical properties. The memory window of SBN thin film was 1.8 V-6.3 V at applied voltage of 3 V-9 V and the leakage current density was 1.5 $\times$ 10$^{-7}$ A/$\textrm{cm}^2$ at applied voltage of 5 V The composition of SBN thin films was analysed by electron probe X-ray micro analyzer(EPMA) and the atomic ratio of Sr:Bi:Nb with pawer ratio of 120 W/100 W was 1:3:2.

• Journal of the Korean Ceramic Society
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• v.42 no.3 s.274
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• pp.150-154
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• 2005

Ferroelectric $Bi_{3.35}Sm_{0.65}Ti_{3}O_{12}(BSmT)$ thin films were synthesized by sol-gel process. In this experiments, $Bi(TMHD)_{3},\;Sm_{5}(O^{i}Pr)_{13},\;Ti(O^{i}Pr)_4$ were used as precursors, which were dissolved in 2-methoxyethanol. The BSmT thin films were deposited on the Pt/TiO/SiO/Si substrates by spin-coating. Thereafter, the thin films with the thickness of 240 nm were annealed from 600 to $720^{\circ}C$ in oxygen atmosphere for 1 h, and post-annealed in oxygen atmosphere for 1 h after deposition of Pt electrode to enhance the electrical properties. To investigate the effects of Sm-substitution in the BTO thin films, the BTO and BSmT thin films were prepared, respectively. The remanent polarization and coercive voltage of the BSmT thin films annealed at $720^{\circ}C$ were $19.48{\mu}C/cm^2$ and 3.40 V, respectively.

• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.183-186
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• 2004

The metal-ferroelectric-insulator-semiconductor(MFIS) capacitors were fabricated using a metalorganic decomposition (MOD)method. The $CeO_2$ thin films were deposited as a buffer layer on Si substrate and $Bi_{3.25}La_{0.75}Ti_3O_{12}$ (BLT) thin films were used as a ferroelectric layer. The electrical and structural properties of the MFIS structure were investigated by varying the $CeO_2$ layer thickness. The width of the memory window in the capacitance-voltage (C-V)curves for the MFIS structure decreased with increasing thickness of the $CeO_2$ layer. Auger electron spectroscopy (AES) and transmission electron microscopy (TEM) show no interdiffusion by using the $CeO_2$ film as buffer layer between the BLT film and Si substrate. The experimental results show that the BLT-based MFIS structure is suitable for non-volatile memory field-effect-transistors (FETs) with large memory window.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.09a
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• pp.9-12
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• 2001

The $Sr_{0.8}Bi_{2.4}Ta_2O_9(SBT)$ thin films are deposited on Pt-coated electrode($Pt/TiO_2/SiO_2/Si$) using RF magnetron sputtering method. With increasing post-annealing temperature from $600[^{\circ}C]$ to $850[^{\circ}C]$, Bi-layered perovskite phase was crystallized above $650[^{\circ}C]$. The maximum remanent polarization and the coercive electric field is 11.60[${\mu}C/cm^{2}$] 48[kV/cm] respectively. The leakage current density of SBT capacitor at post-annealing temperature of $750[^{\circ}C]$ is $1.01{\times}10^{-8}A/cm^2$ at 100[kV/cm]

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.39-40
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• 2005

Ferroelectric Eu-substituted $Bi_4Ti_3O_{12}$ (BET) thin films with a thickness of 200 nm were deposited on Pt(111)/Ti/SiO$_2$/Si(100) substrate by means of the liquid delivery MOCVD system and annealed at several temperatures in an oxygen atmosphere. At annealing temperature above $600^{\circ}C$, the microstructure of layered perovskite phase was observed. The remanent polarization of these films increased with increase in annealing temperature. The remanent polarization values ($2P_r$) of the BET thin films annealed at $720^{\circ}C$ were $37.71{\mu}C/cm^2$ at an applied voltage of 5 V.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.12
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• pp.553-558
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• 2003

The A S $r_{0.7}$B $i_{2.6}$T $a_2$ $O_{9}$ (SBT)thin films are deposited on Pt-coated electrode(Pt/$TiO_2$/$SiO_2$/Si) using a RF magnetron sputtering method. The electrical properties of SBT capacitors with top electrodes were studied. In the XRD pattern, the SBT thin films in all annealing temperatures had (105) orientation. In the SEM images, Bi-layered perovskite phase was crystallized at 75$0^{\circ}C$ and grains largely grew in oxygen annealing atmosphere. The electrical properties of SBT capacitor with top electrodes represent a favorable properties in Pt electrode. The maximum remanent polarization and the coercive electric field with Pt electrode are 12.40C/$\textrm{cm}^2$ and 30kV/cm, respectively. The dielectric constant and leakage current density with Pt electrode is 340 and 6.8110$^{-10}$ A/$\textrm{cm}^2$, respectively.y.y.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.296-296
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• 2007

Ferroelectric neodymium-substituted $Bi_4Ti_3O_{12}$(BTO) thin films have been successfully deposited on Pt/Ti/$SiO_2$/Si substrate by a sol-gel spin-coating process and the effect of crystallization temperature on their microstructure and ferroelectric properties were studied systematically. $Bi(TMHD)_3$, $Nd(TMHD)_3$, $Ti(O^iPr)_4$ were used as the precursors, which were dissolved in 2-methoxyethanol. The thin films were annealed at various temperatures from 600 to $720^{\circ}C$ in oxygen ambient for 1 hr, which was followed by post-annealed for 1 hr after depositing a Pt electrode to enhance the electrical properties. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the crystallinity and surface morphology of layered perovskite phase, respectively. The crystallinity of the BNT films was improved and the average grain size increased as the crystallization temperature increased from 600 to $720^{\circ}C$ at an interval of $40^{\circ}C$. The polarization values of the films were a monotonous function of the crystallization temperature. The remanent polarization value of the BNT thin films annealed at $720^{\circ}C$ was $24.82\;{\mu}C/cm^2$ at an applied voltage of 5 V.