• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1239-1243
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• 1997

A phase analysis in the solid solution of (1-x) PbFe1/2Nb1/2O3-xPbCo1/2W1/2O3 is conducted by dielectric properties, heat capacity and E-P hysteresis at x=0.1 interval. Lattice constants and superlattice intensity are analyzed by the x-ray diffraction, and the temperature - composition phase diagram is determined. The system is found to form a solid solution of perovskite structure throughout the entire composition range, but the nature of phase transitions changes from ferroelectric-paraelectric for $0{\leq}x{\leq}0.5$ to antiferroelectric-paraelectric for $0.6{\leq}x{\leq}1.0$. The transitions of ferroelectric-paraelectric and antiferroelectric-paraelectric for $0.2{\leq}x{\leq}0.5$ and for $0.6{\leq}x{\leq}0.8$, respectively, are diffuse, while those of the ferroelectric-paraelectric and the antiferroelectric-paraelectric for $0.0{\leq}x{\leq}0.1$ and $0.9{\leq}x{\leq}1.0$, respectively are sharp.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.30.1-30.1
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• 2011

Multiferroic thin films with composition $0.9BiFeO_3-0.1Ba(Cu_{1/3}Nb_{2/3})O_3$ were epitaxially grown by pulsed laser deposition on $SrRuO_3(001)/SrTiO_3$ (000) substrate $0.9BiFeO_3-0.1Ba(Cu_{1/3}Nb_{2/3})O_3$, which is assumed to be morphotropic phase boundary (MPB), that showed superior dielectric, ferroelectric and magnetic properties in our study on polycrystalline films. The structures of epitaxially grown films were characterized by means of XRD. From P-E measurements, samples exhibited typical ferroelectric hysteresis loops and large remnant polarization, whose value is much larger than those of pure BFO film. The enhancement of dielectric, ferroelectric, magnetic properties was attributed to the structural distortion induced by the BCN addition and the high physical stress effect.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.245-248
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• 2003

Randomly oriented ferroelectric cerium-substituted $Bi_4Ti_3O_{12}$ thin films have been prepared by using metal-organic decomposition method. The layered perovskite structure was investigated using annealing for 1 h in the temperature range from $550\;{\sim}\;750\;^{\circ}C$. The structure and morphology of the films were characterized using X-ray diffraction and scanning electron microscopy The $Bi_{3.4}Ce_{0.6}Ti_3O_{12}$ (BCeT) thin films showed a perovskite phase and dense microstructure. The grain size of the BCeT films increasedwith increasing annealing temperature. The hysteresis loops of the films were well defined at temperatures above $600\;^{\circ}C$. The 200-nm-thick BCeT thin films annealed at $650\;^{\circ}C$ showed a large remanent polarization (2Pr) of 59.3 ${\mu}C/cm^2$ at an applied voltage of 10 V. The BCeT thin films showed good fatigue endurance up to $5\;{\times}\;10^9$ bipolar cycling at 5 V and 100 kHz.

• Electrical & Electronic Materials
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• v.10 no.10
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• pp.1029-1033
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• 1997

A prototype MFSFET using ferroelectric fluoride BaMgF$_4$as a gate insulator has been successfully fabricated with the help of 2 sheets of metal mask. The fluoride film was deposited in an ultrai-high vacuum system at a substrate temperature of below 30$0^{\circ}C$ and an in-situ post-deposition annealing was conducted for 20 seconds at $650^{\circ}C$ in the same chamber. The interface state density of the BaMgF$_4$/Si(100) interface calculated by a MFS capacitor fabricated on the same wafer was about 8$\times$10$^{10}$ /cm$^2$.eV. The I$_{D}$-V$_{G}$ characteristics of the MFSFET show a hysteresis loop due to the ferroelectric nature of the BaMgF$_4$film. It is also demonstrated that the I$_{D}$ can be controlled by the “write” plus which was applied before the measurements even at the same “read”gate voltage.ltage.

• Korean Journal of Materials Research
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• v.25 no.7
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• pp.317-321
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• 2015

The effects of Nb doping on the crystal structure, microstructure, and dielectric ferroelectric and piezoelectric properties of $(Bi_{0.5}Na_{0.5})_{0.935}Ba_{0.065}Ti_{(1-x)}Nb_xO_3-0.01SrZrO_3$ (BNBTNb-SZ, with ${\chi}=0$, 0.01 and 0.02) ceramics have been investigated. X-ray diffraction patterns revealed that all ceramics have a pure perovskite structure with tetragonal symmetry. The grain size of the ceramics slightly decreased and a change in grain morphology from square to spherical shape was observed in the Nb-doped samples. The maximum dielectric constant temperature ($T_m$) increases with increasing amount of Nb; however, ferroelectric-relaxor transition temperature ($T_{F-R}$) and maximum dielectric constant (${\varepsilon}_m$) values decrease gradually. Nb addition disrupted the polarization hysteresis loops of the BNBT-SZ ceramics by leading a reduction in the remnant polarization coercive field and piezoelectric constant.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.11
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• pp.801-805
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• 2013

In this study, electrocaloric effects of Pb-free $(Ba_{0.85}Ca_{0.15})(Ti_{0.92}Zr_{0.08})O_3$ ferroelectric ceramics were investigated and discussed using the characteristics of P-E hysteresis loops at wide temperature range from room temperature to $140^{\circ}C$. The remnant polarization $P_r$ and coercive field $E_c$ were decreased with increasing temperature. The temperature change ${\Delta}T$ by the electrcaloric effect was calculated by Maxwell's relations, and reached the maximum of ~0.15 at $120^{\circ}C$ under applied electric field of 30 kV/cm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.94-98
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• 2000

Polycrystalline SBTN ferroelectric thin films were prepared by sol-gel method with various Nb mole ratios on Pt/ $SiO_2$/Si (100) substrates. The films were annealed at different temperatures and characterized in terms of phase and microstructure. Relatively a well saturated hysteresis pattern was obtained at x =0.2 in S $r_{0.8}$B $i_{2.3}$(T $a_{1-x}$ N $b_{x}$)$_2$ $O_{9+}$$\alpha$/ thin films. At an applied voltage of 5V, the dielectric constant ($\varepsilon$$_{r}$) and dissipation factor (tan $\delta$) of typical S $r_{0.8}$B $i_{2.3}$(T $a_{1-x}$ N $b_{x}$)$_2$ $O_{9+}$$\alpha$/ thin film (x=0.2) were about 236.2 and 0.034. Measured remanent polarization (2Pr) and coercive field (Ec) were 4.28C/c $m_2$, and 38.88kv/cm respectively. No fatigue was observed up to 6$\times$10$_{10}$ switching cycles at 5V and the normalized polarization reduced by a factor of only 4%.%. 4%.%. 4%.%.%.%.%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.366-367
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• 2006

Different orientated SBN thin films were deposited by Ion Beam Sputtering, and electric properties were measured on each orientation. Ferroelectric $Sr_xBa_{1-x}Nb_2O_6$(SBN) has excellent electro-optic, photo-refractive, piezoelectric, pyroelectric properties. SBN thin film has been deposited by various method, of sol-gel, PLD, CVD, sputtering, etc.. To avoid lead pollution of Pb-system perovskite ferroelectric materials. SBN thin films were fabricated for pyroelectric IR sensor. Using the ceramic target of the same composition and Pt(100)/$TiO_2/SiO-2$/Si(100) substrate, crystallization and orientation behavior as well as electric properties of the films were examined. Seed layer and thin films thickness was controlled to observe the effect on preferred orientation. We measured I-V, C-V, P-E hysteresis to characterize electric-properties on each orientations.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.1
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• pp.48-55
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• 2024

The changes in threshold voltage and DIBL were investigated for changes in remanent polarization P_r and coercive field E_c, which determine the characteristics of the P-E hysteresis curve of ferroelectric in NCFET (negative capacitance FET). The threshold voltage and DIBL (drain-induced barrier lowering) were observed for a junctionless double gate MOSFET using a gate oxide structure of MFMIS (metal-ferroelectric-metal-insulator-semiconductor). To obtain the threshold voltage, series-type potential distribution and second derivative method were used. As a result, it can be seen that the threshold voltage increases when P_r decreases and E_c increases, and the threshold voltage is also maintained constant when the P_r/E_c is constant. However, as the drain voltage increases, the threshold voltage changes significantly according to P_r/E_c, so the DIBL greatly changes for P_r/E_c. In other words, when P_r/E_c=15 pF/cm, DIBL showed a negative value regardless of the channel length under the conditions of ferroelectric thickness of 10 nm and SiO₂ thickness of 1 nm. The DIBL value was in the negative or positive range for the channel length when the P_r/E_c is 25 pF/cm or more under the same conditions, so the condition of DIBL=0 could be obtained. As such, the optimal condition to reduce short channel effects can be obtained since the threshold voltage and DIBL can be adjusted according to the device dimension of NCFET and the P_r and E_c of ferroelectric.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.195-200
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• 2008

This paper presents motion control of the Inchworm composed of the piezoelectric actuators and mechanical elements. Piezoelectric actuator shows nonlinear response characteristics including hysteresis due to the ferroelectric characteristics. This paper proposes feedback control scheme to improve the ability of tracking response to complex input signal and suppress the phenomenon of hysteresis using the sliding mode control technique with the integrator. The sliding mode control system has the limit to minimize both the settle time and overshoot. For making up this limit, this paper also suggests input shaping technique suitable to the inchworm control system.