• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.10
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• pp.876-882
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• 2002

The microstructure and electrical characteristics of ZPCD (ZnO-$Pr_{6}O_{11}$-CoO-$Dy_2O_3$) -based varistor ceramics were investigated with various $Pr_{6}O_{11}$/CoO ratios and sintering temperatures. The density of varistor ceramics with $Pr_{6}O_{11}$=1.0 was almost constant with sintering temperature, whereas it was increased noticeably in $Pr_{6}O_{11}$=0.5. Increasing $Pr_{6}O_{11}$ content enhanced the densification for any CoO content and the density was greatly affected not by CoO content but by $Pr_{6}O_{11}$ content. The varistor ceramics with $Pr_{6}O_{11}$/CoO=0.5/l.0 exhibited a higher nonlinearity than any other composition ratios. In particular, the varistor ceramics sintered at $1350^{\circ}C$ exhibited the best electrical properties, with nonlinear exponent of 37.8, leakage current of 7.6 ${\mu}$A, and tan $\delta$ of 0.059.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.6
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• pp.120-126
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• 1996

In the present study, we have studied on the characteristics of BST thin films with various Ba/Sr ratios by using sol-gel method. Barium-acetate, strontium-acetate and titanium isopropoxide are used as starting materials to fabricate BST thin films by sol-gel method. The fabrication conditions are estabilished through the TG-dT analyses and XRD measurements. BST thin films with the Ba/Sr ratios of 90/10, 70/30, 50/50 and 30/70 were deposited on the Pt/Ta/SiO$_{2}$Si substrate with the estabilished sol-gel process, and their characteristics were examined. The relative permittivity and the leakage current density at 5V vary from 287 to 395 and from 2.3 to 220${\mu}$A/cm$^{2}$, respectively, with various Ba/Sr ratio. Among the films investigatd in this research, BST (70/30) thin film shows the best relative permittivity and dielectric loss of BST (70/30) thin film are 395 and 0.045, respectively and the leakage current density at 5V is 2.3${\mu}$A/cm$^{2}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.320-321
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• 2008

Ferroelectric $SrBi_2Ta_2O_9$(SBT) ceramics were deposite on Pt/Ti/SiO2/Si substrates using a sintered SBT target and then were annealed in the oxygen atmosphere at $750^{\circ}C$, the most excellent characteristics were shown, and the remnant polarization ($2P_r$) value and the coercive electric field ($E_c$) were respectively about 12.40[${\mu}C/cm^2$] and 30[kV/cm]. Moreover, the excellent fatigue characteristic t was little aged even after $10^{10}$ cycles of switchings. The leakage current density and the dielectric constant of the SBT capacitor annealed in the oxygen atmosphere were respectively approximately $2.13\times10^{-9}$ [A/$cm^2$] and 340.

• Journal of Information Display
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• v.8 no.3
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• pp.5-10
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• 2007

Twin target sputtering (TTS) system with a configuration of vertically parallel facing Al targets and a substrate holder perpendicular to the Al target plane has been designed to realize a direct Al cathode sputtering on organic light emitting diodes (OLEDs). The TTS system has a linear twin target gun with ladder type magnet array for effective and uniform confinement of high density plasma. It is shown that OLEDs with Al cathode deposited by the TTS show a relatvely lower leakage current density $({\sim}1{\times}10^{-5}mA/cm^2)$ at reverse bias of -6V, compared to that ($1{\times}10^{-2}{\sim}10^{-3}$ $mA/cm^2$ at -6V) of OLEDs with Al cathodes grown by conventional DC magnetron sputtering. In addition, it was found that Al cathode films prepared by TTS were amorphous structure with nanocrystallines due to low substrate temperature. This demonstrates that there is no plasma damage caused by the bombardment of energetic particles. This indicates that the TTS system with ladder type magnet array could be useful plasma damage free deposition technique for direct Al cathode sputtering on OLEDs or flexible OLEDs.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1087-1098
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• 2019

In this paper, a detuning factor (DeFac) method is proposed to design the key parameters for optimizing the transfer power and efficiency of an Inductively Coupled Power Transfer (ICPT) system with primary-secondary side compensation. Depending on the robustness of the system, the DeFac method can guarantee the stability of the transfer power and efficiency of an ICPT system within a certain range of resistive-capacitive or resistive-inductive loads. A MATLAB-Simulink model of a ICPT system was built to assess the system's main evaluation criteria, namely its maximum power ratio (PR) and efficiency, in terms of different approaches. In addition, a magnetic field simulation model was built using Ansoft to specify the leakage flux and current density. Simulation results show that both the maximum PR and efficiency of the ICPT system can reach almost 70% despite the severe detuning imposed by the DeFac method. The system also exhibited low levels of leakage flux and a high current density. Experimental results confirmed the validity and feasibility of an ICPT system using DeFac-designed parameters.

• Journal of the Korean Physical Society
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• v.73 no.12
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• pp.1879-1883
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• 2018

We analyzed the deep-trap states of GaN/InGaN ultraviolet light-emitting diodes (UV LEDs) before and after electrical stress. After electrical stress, the light output power dropped by 5.5%, and the forward leakage current was increased. The optical degradation mechanism could be explained based on the space-charge-limited conduction (SCLC) theory. Specifically, for the reference UV LED (before stress), two sets of deep-level states which were located 0.26 and 0.52 eV below the conduction band edge were present, one with a density of $2.41{\times}10^{16}$ and the other with a density of $3.91{\times}10^{16}cm^{-3}$. However, after maximum electrical stress, three sets of deep-level states, with respective densities of $1.82{\times}10^{16}$, $2.32{\times}10^{16}cm^{-3}$, $5.31{\times}10^{16}cm^{-3}$ were found to locate at 0.21, 0.24, and 0.50 eV below the conduction band. This finding shows that the SCLC theory is useful for understanding the degradation mechanism associated with defect generation in UV LEDs.

• Korean Journal of Materials Research
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• v.28 no.8
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• pp.440-444
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• 2018

An effective cleaning method for Ni removal in Ni-induced lateral crystallization(Ni-MILC) poly-Si TFTs and their electrical properties are investigated. The HCN cleaning method is effective for removal of Ni on the crystallized Si surface, while the nitric acid treatment results decrease by almost two orders of magnitude in the Ni concentration due to effective removal of diffused Ni mainly in the poly-Si grain boundary regions. Using the HCN cleaning method after the nitric acid treatment, re-adsorbed Ni on the Si surfaces is effectively removed by the formation of Ni-cyanide complexions. After the cleaning process, important electrical properties are improved, e.g., the leakage current density from $9.43{\times}10^{-12}$ to $3.43{\times}10^{-12}$ A and the subthreshold swing values from 1.37 to 0.67 mV/dec.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05d
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• pp.77-81
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• 2003

The $Sr_{0.7}Bi_{2.6}Ta_2O_9$(SBT) thin films are deposited on Pt-coated electrode(Pt/$TiO_2/SiO_2$/Si) using RF magnetron sputtering method. The structural and electrical properties of SBT capacitors were influenced with annealing atmosphere. In the XRD pattern, the SBT thin films in all annealed atmosphere had (105) orientation. In the SEM images, Bi-layered perovskite phase was crystallized in all annealing atmosphere and grains largely grew in oxygen annealing atmosphere. The dielectric constant and leakage current density of capacitors annealed oxygen atmosphere are 340 and $2.13{\times}10^{-9}[A/cm^2]$ respectively.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.6
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• pp.1175-1177
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• 2011

The SBN thin films were deposited on Pt/Ti/$SiO_2$/Si and p-type Si(100) substrate by rf magnetron sputtering method using $Sr_{0.7}Bi_{2.3}Nb_2O_9$ ceramic target. SBN thin films deposited were annealed at 600~800[$^{\circ}C$] by furnace in oxygen atmosphere during 40min. The polarization characteristics have been investigated to confirm the possibility of the SBN thin films for the application to destructive read out ferroelectric random access memory. The maximum remanent polarization and the coercive voltage are 0.6[${\mu}C/cm^2$], 1.2[V] respectively at annealing temperature of 800[$^{\circ}C$]. The leakage current density was the $2.57{\times}10^{-6}[A/cm^2]$ at an applied voltage of 5[V] at annealing temperature of 650[$^{\circ}C$]. Also, the fatigue characteristics of SBN thin films did not change up to $10^8$ switching cycles.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.10
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• pp.35-41
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• 1992

Ultra-thin silicon nitride films were fabricated with ECR(Electron cyclotron Resonance) nitrogen plasma at room temperature. Film thickness was about 50$\AA$ after nitridation for 1min at microwave power of 1000W, RF power of 500W, and NS12T pressure of ${\times}10^{-3}$ torr. 50$\AA$ fo nitride film was grown within 1 min and no appreciable growth occured thereafter. Dielectric breakdown strength and leakage current density in Al/SiN/Si structure were measured to be about 7-11 MV/cm and ${\times}10^{-10}~5{\times}10^{-10}A/cm^{2}$, respectively. Observed linear relationship in 1n(J/E)-vs-E$^{1/2}$ and no polarity-dependence of the leakage current indicated that the Poole-Frenkel emission is mainly responsible for the conduction in this nitrided silicon films.