• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.4
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• pp.319-324
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• 2002

In this study, the reduce of plasma etching damage in PZT thin film with addictive gas and re-annealing after etching have been investigated. The PZT thin films were etched as a function of $Cl_2/CF_4$ with addition of Ar and $O_2$ with inductively coupled plasma. The etch rates of PZT thin films were 1450 ${\AA}/min$ at 30% additive Ar and 1100 ${\AA}/min$ at 10% auditive $O_2$ into $Cl_2/CF_4$ gas mixing ratio of 8/2. In order to reduce plasma damage of PZT thin films after etching, the etched PZT thin films were re-annealed at various temperatures at $O_2$ atmosphere. From the hysteresis curries, the ferroelectric properties are improved by $O_2$ re-annealing process. The improvement of ferroelectric behavior at annealed PZT films is consistent wish the increase of the (100) and (200) PZT peaks revealed by x-ray diffraction (XRD). From x ray photoelectron spectroscopy (XPS) analysis, the intensity of Pb-O, Zr-O and Ti-O peak are increased and the chemical residue peak is reduced by $O_2$ re-annealing. The ferroelectric behavior consistent with the dielectric nature of $Ti_xO_y$ is recovered by $O_2$ recombination during rapid thermal annealing process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.639-643
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• 2004

[ $Ta_2O_5$ ]가 첨가된 $Ba(Zn_{1/3}Ta_{2/3})O_3$[BZT] 세라믹은 1:2 규칙화 정도가 증가하고 $Ba_3Ta_5O_{15}의 이차상이 새롭게 형성된다. $1580^{\circ}C$ 보다 높은 온도에서 소결된 BZT 세라믹은 $Ta_2O_5$를 첨가하면 입자의 성장이 일어나고 액상이 형성된다. 품질계수(Q) 값은 $1580^{\circ}C$ 보다 높은 온도에서 소결할 경우 미량의 $Ta_2O_5$ 첨가만으로도 상당히 증가한다. 상대밀도는 $Ta_2O_5$ 첨가량에 따라 감소하기 때문에 Q값의 증가는 상대밀도와는 무관하다. 반면에, $Ta_2O_5$의 첨가량에 따라 입자의 성장은 증가하였기 때문에 Q값의 향상은 입자크기와 관계가 있음을 알 수 있다. 많은 양의 $Ta_2O_5$ 첨가시 비록 입자 크기가 증가했음에도 불구하고 Q값이 매우 낮은 것을 볼 때, Q값의 감소는 $Ba_3Ta_5O_{15}$ 상의 영향과 낮은 밀도 값에 기인한 것이다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.310-310
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• 2008

본 연구에서는 (1-x) Pb(Zr0.515Ti0.485)$O_3$ - x Pb$(Sb_{1/2}Nb_{1/2})O_3$ + 0.5wt% $MnO_2$ 조성에 Pb$(Sb_{1/2}Nb_{1/2})O_3$ (PSN) (x=0.02, 0.04, 0.06, 0.08) 변화에 따른 미세구조 및 압전, 유전특성에 관해 고찰하였다. PSN 치환량이 증가함에 따라 정방정 (tetragonal)구조에서 삼방정(rhombohedral)구조로 상전이가 일어났으며, 결정립의 크기가 작아지는 것을 확인하였다. 전기기계결합계수 (kp) 는 PSN이 4 mol % 치환됨에 따라 증가하였으며, 더 이상 치환 시 감소하였다. PSN 치환에 따른 전기적 특성은, 결정구조, 결정립의 크기 및 2 차상 등의 미세구조와 긴밀한 관계가 있는 것으로 보여진다. 상경계(Morphotropic Phase Boundary) 영역인 0.96 Pb(Zr0.515Ti0.485)$O_3$ - 0.04 Pb$(Sb_{1/2}Nb_{1/2})O_3$ + 0.5wt% $MnO_2$ 조성에서 $\varepsilon{^T}_{33}/\varepsilon_o$ = 1109, $k_p$= 70.8 (%), $d_{33}$= 325 (pC/N)의 우수한 특성을 나타내었다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.9
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• pp.783-787
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• 2002

In recent year, B $i_{4-}$x L $a_{x}$ $Ti_3$ $O_{12(BLT)}$ is one of promising substitute materials for the ferroelectric random access memory(FRAM) applications. But the systematic composition is still insufficient, so this experiment was carried out in ceramic ambient sintering process which has the very excellent ferroelectric property. Samples were prepared by a bulk and the purpose which was estimated with a suitability of thin films applications. The density of B $i_{3.75}$ L $a_{0.25}$ $Ti_3$ $O_{12}$ was high and the XRD pattern showed that the intensity of main peak (117) was increased at the argon ambient sintering. Controlling the quantity of oxygen, crystallization showed a thin, long plate like type, and we obtained the excellent dielectric and polarization properties at the argon atmosphere sintering. Also this sintering process was effective at the bulk sample. Argon ambient sintered sample produced higher permittivity of 154, the remanent polarization(2Pr) of 6.8 uC/$\textrm{cm}^2$ compared with that sintered in air and oxygen ambient. And this sintering process showed a possibility which could be applied to thin films process..

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.1
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• pp.35-39
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• 2019

In this study, we investigated the optimum calcination temperature of lead-free $0.74(Bi_{0.5}Na_{0.5})TiO_3-0.26SrTiO_3$(BNST) piezoelectric ceramics by analyzing the crystal structure, dielectric properties, and electric field-induced strain behavior. BNST ceramics prepared by conventional solid-state reaction methods at various calcination temperatures according to the industrial standard. All samples of BNST ceramics were subsequently sintered at $1,175^{\circ}C$ for 2 h. Crystal structure classification of the ceramics showed a single perovskite phase, with no second phase detectable for the samples calcined at $750^{\circ}C$ or higher. BNST samples calcined at $850^{\circ}C$ exhibited the most optimal values for itsand the common physical parameters of $density=5.518g/cm^3$, ${\varepsilon}=1,871.837$, $tan{\delta}=0.047$, and ${d_{33}}^*=874pm/V$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.5
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• pp.337-343
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• 2020

This study investigated the low temperature sintering with various templates of Bi-based lead-free piezoelectric ceramics. The effects of using CuO-coated Na_0.5Bi_4.5Ti₄O₁₅ templates on the sintering behavior as well as the dielectric, ferroelectric, and piezoelectric properties of Bi_1/2(Na_0.78K_0.22)_1/2TiO₃ (BNKT) ceramics have been examined. In comparison with the specimens sintered with the Na_0.5Bi_4.5Ti₄O₁₅ templates without CuO coating, those sintered with the CuO-coated Na_0.5Bi_4.5Ti₄O₁₅ templates showed larger template sizes as well as a larger electric field induced strain (S_max/E_max) of 422 pm/V after sintering at temperatures as low as 975℃. These results are promising for low-cost multilayer ceramic actuator applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.117-120
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• 1998

In this study, $Al_2O_3/MgO$ bilayer was prepared with Electron-beam evaporation and the properties of the film was investigated in order to improve the property of MgO film, which is used for the protection layer in PDP(P1asma Display Panel). The thickness of $Al_2O_3/MgO$ bilayer was optimized by the Matrix Theory for the fabrication of antireflection structure for 5350A wavelength. The secondary electron emission yields of as-deposited film and annealed film were measured and compared, the bilayer was considered for the applicability as PDP. XRD showed the strong (200) primary peak of MgO. The intensity of (200) peak in the film annealed at 300C was decreased. As the result of SEM analysis for MgO films and Alz03 films, it is considered that the morphology of the films were improved of roughness and it were condensed by annealing.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.4
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• pp.87-95
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• 1999

A primary limitation of the awlication of New class of solid state high power, high speed electronic device, narrely, the Photo-Conductive Power Switch(PCPS) is that the switches flashover at the surlace under average awlied fields much less than the bulk breakdown field of the semiconductor in most cases. The only way overcome those problffi1 and has a workable compact solid state switch is to passivate the surlace by a solid state dielectric material. In this experirrentation, The voltage withstands of Silicon is to be severely degraded when operated in vacuum(10[kV/cm]) and the perlormance is improved when operated in air(30[kV/cm[), in SF6(80~100[kV/cm]). After the passivation, the device had a breakdown field in vacuum and air at a field as high as the unpassivated device in SF6. A experirrent results show passivated devices have excellent breakdown field. In this paper, We improved the main properties and mechanism of the silicon breakdown before and after passivation under high field. field.

• Korean Journal of Materials Research
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• v.18 no.4
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• pp.169-174
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• 2008

The structural and electrical properties of amorphous $BaSm_2Ti_4O_{12}$ (BSmT) films on a $TiN/SiO_2/Si$ substrate deposited using a RF magnetron sputtering method were investigated. The deposition of BSmT films was carried out at $300^{\circ}C$ in a mixed oxygen and argon ($O_2$ : Ar = 1 : 4) atmosphere with a total pressure of 8.0 mTorr. In particular, a 45 nm-thick amorphous BSmT film exhibited a high capacitance density and low dissipation factor of $7.60\;fF/{\mu}m2$ and 1.3%, respectively, with a dielectric constant of 38 at 100 kHz. Its capacitance showed very little change, even in GHz ranges from 1.0 GHz to 6.0 GHz. The quality factor of the BSmT film was as high as 67 at 6 GHz. The leakage current density of the BSmT film was also very low, at approximately $5.11\;nA/cm^2$ at 2 V; its conduction mechanism was explained by the the Poole-Frenkel emission. The quadratic voltage coefficient of capacitance of the BSmT film was approximately $698\;ppm/V^2$, which is higher than the required value (<$100\;ppm/V^2$) for RF application. This could be reduced by improving the process condition. The temperature coefficient of capacitance of the film was low at nearly $296\;ppm/^{\circ}C$ at 100 kHz. Therefore, amorphous BSmT grown on a TiN substrate is a viable candidate material for a metal-insulator-metal capacitor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.324-327
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• 2005

An electrophoretic display using $TiO_2$ particles is the most promising candidate because it offers various advantages such as ink-on-paper appearance, good contrast ratio, wide viewing angle, image stability in the off-state and extremely low power consumption. The core technology of electrophoretic display is the dispersion controlling of $TiO_2$ nano particles in nonaqueous solution. To prepare an ink for electronic paper using electrophoretic properties of $TiO_2$ nano particles, cyclohexane with low dielectric constant and transparency, polyethylene for producing polymer coating layer which reduces apparent gravity of $TiO_2$, and $TiO_2$ powders were mixed together by planetary-mill. The zeta-potential value of $TiO_2$ particles in cyclohexane was measured about -40mV, but was measured over -110mV by dispersant attached to polyethylene-coated $TiO_2$ surface. Prepared electronic ink was filled in cross patterned micro-wall with $200{\mu}m$ in width and $40{\mu}m$ in height on ITO glass designed by photolithography. The response time of electronic paper evaluated by mobility of $TiO_2$ particle between micro-walls was measured 0.067sec, but the drift velocity from reflectance wave form during reverse from of electronic ink was measured 0.07cm/sec.