• Journal of the Korean Ceramic Society
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• v.34 no.6
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• pp.620-628
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• 1997

The possibility of the existence of a field-induced micro-macrodomain switching was proposed and examined using 9 mol % PbZrO3-doped 0.6Pb(Ni1/3Nb2/3)O3-PbTiO3 (PNN-PT) systems having rhombohedral symmetry at room temperature. the thermally depoled (freshly prepard) specimens prepared from the rhombohedral side of the system exhibited a relaxor behavior for the whole range of temperature examined (for T

• Journal of electromagnetic engineering and science
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• v.11 no.4
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• pp.239-249
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• 2011

In this paper, we propose a reliable $8{\times}8$ up-down switching polar relay code based on 3GPP LTE standard, motivated by 3GPP LTE down link, which is 30 bps/Hz for $8{\times}8$ MIMO antennas, and by Arikan's channel polarization for the frequency selective fading (FSF) channels with the generator matrix $Q_8$. In this scheme, a polar encoder and OFDM modulator are implemented sequentially at both the source node and relay nodes, the time reversion and complex conjugation operations are separately implemented at each relay node, and the successive interference cancellation (SIC) decoder, together with the cyclic prefix (CP) removal, is performed at the destination node. Use of the scheme shows that decoding at the relay without any delay is not required, which results in a lower complexity. The numerical result shows that the system coded by polar codes has better performance than currently used designs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.3
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• pp.175-180
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• 2016

In this study, we proposed an optical compensation method to improve the symmetricity of contrast ratio for wide viewing angle IPS (in-plane switching) LCD. First, the phase retardation depending on the thickness of compensation film is calculated, and then the phase change is presented at the $Poincar{\acute{e}}$ sphere. The phase retardation and the polarization state of the light passing through the optical elements are caculated by using the EJMM (extended Jones matrix method). In addition, the transmittance and the contrast countour are also calculated by using the Berremann's $4{\times}4$ matrix method. The simulation is carried out for a IPS LC cell with positive A/C/A compensation film. From the standard deviation of the contrast ratio, we confirmed the symmetricity at each viewing angle is inversely proportional to the standard deviation and calculated the optimum design condition of the uniaxial compensation film for the IPS LCD.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.200-203
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• 2003

Ferroelectric europium-substitution $Bi_4Ti_3O_{12}$ thin films were fabricated by spin-coating onto a Pt/Ti/$SiO_2$/Si substrate. The $Bi_{3.25}Eu_{0.75}Ti_3O_{12}$ (BET) films have polycrystalline structure annealed at 700 C. We investigated that the influence of $Bi_4Ti_3O_{12}$ thin films by substituting for Bi ions with Bi ions using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). From the XPS measurement, it was suggested that the stability of the metal-oxygen octahedral should be related to substitute for Bi ions with Eu ions at annealed $800^{\circ}C$. The BET thin films showed a large remanent polarization (2Pr) of $60.99C/cm^2$ at an applied voltage of 10 V. The BET thin films exhibited no significant degradation of switching charge at least up to $5{\times}10^9$ switching cycles at a frequency of 50 kHz.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.341-342
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• 2006

Gadolinium-substituted bismuth titanate, $Bi_{3.3}Gd_{0.7}Ti_3O_{12}$ (BGT), thin films were successfully fabricated on Pt(111)/Ti/$SiO_2$/Si substrates by a sol-gel method and their structural and ferroelectric properties have been characterized. Fabricated BGT thin films were found to be random orientations, which were confirmed by X-ray diffraction experiment and scanning electron microscope analysis. The remanent polarization ($2P_r$)) of BGT thin film annealed at $720^{\circ}C$ was $25.85\;{\mu}C/cm^2$ at an applied voltage of 5 V. The BGT thin films exhibited a 11 % reduction in their switching charge after no less than $10^{11}$ switching cycles at a frequency of 1 MHz.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.6
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• pp.24-33
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• 2000

Switching behaviour of the ferroelectric thin film and device characteristics of the MFSFET(Metal-Ferroelectric-Semiconductor FET) are simulated with taking into account the accumulation of oxygen vacancies near interface between the ferroelectric thin film and the bottom electrode caused by the progress of fatigue. In our switching model, relative switched charge is 0.74 nC before fatigue, but after the progress of fatigue it reduces to 0.15 nC with the generation of oxygen vacancies. It indicates that the generation of oxygen vacancies strongly suppresses polarization reversal. $C-V_G\;and\;I_D-V_G$ curves in our MFSFET device model exhibit the memory window of 2 V and show the accumulation, the depletion and the inversion regions in capacitance characteristic clearly. The difference of saturation drain current of the device before fatigue in shown by the dual threshold voltages in $I_D-V_G$ curve as 6nA/$cm^2$ and decreases as much as 50% after fatigue. Decrease of the difference of saturation drain currents by fatigue implies that the accumulation of oxygen vacancies with the fatigue should be avoided in the device application. Our simulation model is expected to play an important role in estimation of the behavior of MFSFET device with various ferroelectric thin films.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.4
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• pp.151-154
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• 2004

Issues of ferroelectric high-density memories (>64 Mb) indispensable for upcoming ubiquitous era have been on the cell integration less than $0.1\;\mu\textrm{m}^2$ and reliabilities. Thus nanoscale control of microstructures of ferroelectric films with large switching polarization has been one of the issues to obtain the uniform electrical properties for realization of high-density memories. In this study the grain orientations and distributions of BT-based films by spin-on coatings were examined by FEG-SEM/EBSD. Ferroelectric domain characteristics by PFM were also performed to study the dependence of reliabilities on the grain orientations and distributions. It is believed that understandings of the nucleation and growth mechanisms of the a- or b-axis oriented films during the thermal processes such as RTA and furnace annealing affecting on grain orientation and uniformity could be possible based on our experimental results.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.595-599
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• 2003

We have studied the phase transition to look for molecular structure by using several different techniques for new banana-shaped liquid crystals shown in Fig. 1. Based on the similarities to recently observed fluro-contaning materials (switching involves layer structure rearrangement, increasing threshold with increasing temperature) for HC sample (where x is H), we assume that the phase C has a triclinic symmetry corresponding to the double tilted $smC_G$ Phase. The observation that the polarization peak appears at lower field ($E_o{\sim}15V/{\mu}m$) than the amplitude of the threshold ($E_{th}$) can be explained assuming a field induced $SmC_G$ - SmCP (or SmAP) transition at $E_{th}$

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.435-440
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• 2001

Piezoelectric solids such as PZT and PLZT have been widely used as sensors and actuators for various smart systems. One of the problems arising in actuator applications is that a larger actuation force needs to be produced from a small system. This naturally leads to local electric field or stress concentration and thereby resulting in a nonlinear behavior inside the system, Hence, it becomes more important to predict the nonlinear behavior of piezoelectric solids. In this paper we investigate the mechanism of nonlinear behavior in those materials and suggest a constitutive and finite element model. The calculation results obtained from the model seem to be qualitatively consistent with experiments.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.4-5
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• 2001

Advent of lasers offering high intensity beam has opened the glass to the nonlinear optic (NLO). The high electric field associated with such laser beams can be so large that high order components of the glass polarization can be measured. Such development is of scientific and technological interests in particular in systems involving an intensity-dependent refractive index and/or ultra-fast response (＜10$\^$-12/s). From a scientific viewpoint the NLO response intensity must be understood as a function of the glass composition. On the other hand, large family of applications are presently under investigation in various fields of optical materials or systems e.g. laser glasses for fusion energy, soliton propagation for ultra-long distances, ultra-fast-switching, optical storage etc....(omitted)