• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.11a
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• pp.45-48
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• 2000

High dielectric (Ba,Sr)TiO$_3$thin films were etched in an inductively coupled plasma (ICP) as a function of C1$_2$/Ar gas mixing ratio. Under Cl$_2$(20)/Ar(80), the maximum etch rate of the BST films was 400$\AA$/min and selectivities of BST to Pt and PR were obtained 0.4 and 0.2, respectively. We investigated the etched surface of BST by x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and x-ray diffraction (XRD). From the result of XPS analysis, we found that residues of Ba-Cl and Ti-Cl bonds remained on the surface of the etched BST for high boiling point. The surface roughness decreased as Cl$_2$increases in C1$_2$/Ar plasma because of non-volatile etching products. This changed the nature of the crystallinity of BST. From the result of XRD analysis, the crystallinity of etched BST film maintained as similar to as-deposited BST under Ar only and Cl$_2$(20)/Ar(80). However, (100) orientation intensity of etched BST film abruptly decreased at Cl$_2$only plasma. It was caused that Cl compounds were redeposited on the etched BST surface and damaged to crystallinity of BST film during the etch process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.45-48
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• 2000

High dielectric (Ba,Sr)TiO$_3$ thin films were etched in an inductively coupled plasma (ICP) as a function of C1$_2$/Ar gas mixing ratio. Under Cl$_2$(20)/Ar(80), the maximum etch rate of the BST films was 400$\AA$/min and selectivities of BST to Pt and PR were obtained 0.4 and 0.2, respectively. We investigated the etched surface of BST by x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and x-ray diffraction (XRD). From the result of XPS analysis, we found that residues of Ba-Cl and Ti-Cl bonds remained on the surface of the etched BST for high boiling point. The surface roughness decreased as Cl$_2$ increases in Cl$_2$/Ar plasma because of non-volatile etching products. This changed the nature of the crystallinity of BST. From the result of XRD analysis, the crystalliility of etched BST film maintained as similar to as-deposited BST under Ar only and Cl$_2$(20)/Ar(80). However, (100) orientation intensity of etched BST film abruptly decreased at Cl$_2$ only plasma. It was caused that Cl compounds were redeposited on the etched BST surface and damaged to crystallinity of BST film during the etch process.

• Progress in Superconductivity and Cryogenics
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• v.7 no.1
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• pp.13-16
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• 2005

High temperature superconductor, $\YBa_2Cu_3O_{7-x}$ (YBCO) and ferroelectric, $\Ba_{0.1}Sr_{0.9}TiO_{3}$ (BST) multilayer thin films were deposited using on MgO(100) substrates pulsed laser deposition. The thin films exhibited only (001) peaks of YBCO and 1357 The HTS thin films demonstrated excellent zero resistance temperature of 92.5 K. We designed and fabricated HTS ferroelectric phase shifter using high frequency system simulator and standard photolithography method, respectively The HTS phase shifter shows a low insertion loss (2.97 dB) and large phase change ($\162^{circ}$) with 40 V do bias at 10 GHz. The HTS phase shifter shows 54 of figure of merit. These results can be applicable to phased anay antenna system for satellite communication services.

• Journal of the Korean Ceramic Society
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• v.37 no.4
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• pp.302-307
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• 2000

The objective of this study was to investigate the sintering behavior, crystallization characteristic of glass-ceramic and optimal sintering condition on the glass/ceramic composite for fabricating substrate of LTCC. Glass/ceramic composite was made from alumina powder and glass frit, which was composed of SiO2-TiO2-RO-PbO/(R: Ba, Sr, Ca), and was sintered for 0, 30, 60minutes in the temperature range from 700$^{\circ}C$ to 1000$^{\circ}C$. Properties of frit and glass/ceramic compsoite were analyzed by DTA, XRD, SEM and Network Analyzer and so on. Main sintering mechanism was densification occurred above 730$^{\circ}C$ by viscous flow and crystallization starting about 780$^{\circ}C$ affected sintering also. So viscous flow was affected by sintering temperature, duration time, and creation of crystallization phase etc. From this study, it was possible to fabricate glass/ceramic composite by changing sintering temperature and duration time.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.4
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• pp.63-69
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• 1999

The electrical properties of rf-magnetron sputtered $Ba_{0.5}Sr_{0.3}TiO_3$ (BST) capacitors were investigated by varying annealing temperature and atmosphere of the rapid thermal annealing (RTA). The electrical properties of Pt/BST/Pt capacitors were found to strongly depend on the RTA condition. It seems that the dependence of the electrical properties of the Pt/BST/Pt capacitors on the RTA condition is related to the oxygen vacancies in BST thin films. In order to clarify the relation between the oxygen vacancies and the electrical properties of Pt/BST/Pt capacitors, we have examined the two different annealing methods. One annealing method was performed in $O_2$ gas and the other was done in $O_2$-plasma at the same condition of 450$^{\circ}C$, 20 mtorr. It was found that the leakage current densities of $O_2$-plasma annealed capacitor were much lower than those of $O_2$ annealed capacitor. The dielectric constants of $O_2$ annealed capacitor decreased about 14% comparing with those of as-deposited. In contrast, there was no decrease in the dielectric constant of $O_2$-plasma annealed. These results indicate that $O_2$-plasma annealing is very effective in compensation the oxygen vacancies in BST thin films. It can be also concluded that the oxygen vacancies greatly affect the electrical properties of Pt/BST/Pt capacitors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.19-20
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• 2007

At first the $Ba_{0.5}Sr_{0.5}TiO_3$-MgO powder with $B_2O_3-Li_2CO_3$ were made by the Sol-Gel method. The thick films of BST-MgO with $B_2O_3-Li_2CO_3$ were fabricated on the $Al_2O_3$ substrates coated with Pt by the screen printing method. The structural and dielectric properties of the BST-MgO thick film with $B_2O_3-Li_2CO_3$, addition were investigated. The structure of the BST-MgO with $B_2O_3-Li_2CO_3$ thick films were dense and homogeneous with no pores. The dielectric constant was increased and dielectric loss was decreased with increasing the sintering temperature.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1261-1262
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• 2007

At first the $Ba_{0.5}Sr_{0.5}TiO_{3}$-MgO powder with $B_{2}O_{3}-Li_{2}CO_{3}$ were made by the Sol-Gel method. And then the thick films of BST-MgO with $B_{2}O_{3}-Li_{2}CO_{3}$ were fabricated on the $Al_{2}O_{3}$ substrates coated with Pt by the screen printing method. The structural and dielectric properties of the BST-MgO thick film with $B_{2}O_{3}-Li_{2}CO_{3}$ addition were investigated. The structure of the BST-MgO with $B_{2}O_{3}-Li_{2}CO_{3}$ thick films were dense and homogeneous with no pores. The dielectric constant and dielectric loss were increased with decreasing the $B_{2}O_{3}-Li_{2}CO_{3}$ addition ratio.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.1144-1147
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• 2002

Ferroelectric $Sr_xBa_{1-x}Nb_2O_6(0.25{\leq}x{\leq}0.75)$ thin films were prepared by the Ion Beam Sputtering method. Deposit onto Pt/Ti/$SiO_2$/Si(100) substrates. The deposited thin films were heat-treated for crystallization. Microstructure and crystallization behavior were examined using FE-SEM, XRD. Ferroelectric hysteresis were measured. The measured remanent polarization and coercive field values were $38{\mu}C/cm^2$ and 120kV/cm, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.309-312
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• 2002

Ferroelectric $Sr_{0.3}Ba_{0.7}Nb_{2}O_{6}$ (SBN30) thin films were deposited on Pt/Ti/$SiO_{2}$/Si(100) substrates by ion beam sputtering. During annealing treatment at $750^{\circ}C$, poling was attempted by applying dc voltage bias across polished surfaces. Phase relation, microstructure and crystallization behavior were examined using XRD and FE-SEM. Ferroelectric hysteresis characteristics were also determined where both remanent polarization and coercive values decreased with the increase of bias voltage. The measured remanent polarization and coercive field values at 5 V and 10 V bias were $36{\mu}C/cm^2$, $10{\mu}C/cm^2$ and 100kV /cm, 80kV /cm, respectively.

• Proceedings of the Materials Research Society of Korea Conference
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• 1998.08a
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• pp.41.4-41
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• 1998