• Journal of information and communication convergence engineering
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• v.3 no.4
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• pp.179-183
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• 2005

A photodiode capable of obtaining a sufficient photo/ dark current ratio at both forward bias state and reverse bias state is proposed. The photodiode includes a glass substrate, an aluminum film formed as a lower electrode over the glass substrate, an alumina film formed as an insulator barrier over the aluminum film, a hydrogenated amorphous silicon film formed as a photo conduction layer over a portion of the alumina film, and a transparent conduction film formed as an upper electrode over the hydro-generated amorphous silicon film. A good quality alumina $(Al_2O_3)$ film is formed by oxidation of aluminum film using electrolyte solution of succinic acid. Alumina is used as a potential barrier between amorphous silicon and aluminum. It controls dark-current restriction. In case of photodiodes made by changing the formation condition of alumina, we can obtain a stable dark current $(\~10^{-12}A)$ in alumina thickness below $1000{\AA}$. At the reverse bias state of the negative voltage in ITO (Indium Tin Oxide), the photo current has substantially constant value of $5{\times}10^{-9}$ A at light scan of 100 1x. On the other hand, the photo/dark current ratios become higher at smaller thicknesses of the alumina film. Therefore, the alumina film is used as a thin insulator barrier, which is distinct from the conventional concept of forming the insulator barrier layer near the transparent conduction film. Also, the structure with the insulator thin barrier layer formed near the lower electrode, opposed to the ITO film, solves the interface problem of the ITO film because it provides an improved photo current/dark current ratio.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1168-1170
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• 1995

The purpose of this thesis is to fabricate the hexamethyldisiloxane thin film by plasma polymerization method, and to investigate the electric conduction characteristics of plasma polymerized thin film. Current density was measured in being changed annealing temperature(room temperature${\sim}125[^{\circ}C]$) and electric field intensity($10^5{\sim}1.2{\times}10^6$[V/cm]). The current density of thin films fabricated at discharge power of $30{\sim}90$[W] showed $1.3{\times}10^{-11}{\sim}3.1{\times}10^{-12}[A/cm^2]$ after 10 minutes of permission of electric field. The current density increased gradually with increasing of annealing temperature and electric field intensity. The electric conduction type of thin films fabricated in discharge power of 90[W] agreed with Schottky type.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.4
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• pp.297-304
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• 2013

This paper presents a improved control technique to overcome disadvantage when the inductor current of boost converter in PV system becomes DCM(Discontinuous Conduction Mode) due to the low insolation. MPPT(Maximum Power Point Tracking) output reference voltage could not be exactly followed by conventional dual-loop PI control method used typically because of the error between the actual current and measured current. Therefore, in this paper, Hybrid controller that changes the control method in DCM and CCM(Continuous Conduction Mode), and single state feedback controller are used to compensate that problem. The proposed control technique was verified by simulation using PSIM 9.0 and experiments.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.1
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• pp.13-18
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• 2000

We have fabricated LB ultra-thin films of maleate system by LB technique and evaluated the deposited status of LB ultra-thin films by I-V characteristics such as capacitance. It was found that the thickness of LB ultra-thin per layer is $27~30[{\AA}]$ by XRD. And, we have known that the conductivity along the horizontal direction of LB ultra-thin films was about $10^{-8}[S/cm]$, it corresponds to the semiconducting materials. Also, the I-V characteristics along the vertical direction of LB ultra-thin films was dominated by Schottky type current, the activation energy obtained by current-temperature characteristics was about 0.84[eV] and the conductivity was about $10^{-14}[S/cm]$, it corresponds to the insulator. And, the anisotropic conduction mechanism of the LB ultra-thin films in vertical direction and horizontal direction is determined by the hydrophilic group and the hydrophobic group in LB ultra-thin films. The above results are applicable to the semiconductor devices such as switching device, which function at the molecular level.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.9
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• pp.757-761
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• 2001

We studied emitting properties of organic electroluminescent devices fabricated using the spin-coating and Langmuir-Blodgett(LB) technique. The LB technique has the advantage of precise control of the thickness better than spin-coating method. LB monolayer of poly(3-hexylthiophene)(P3HT) was deposited 27 layers onto the indium-tin-oxide(ITO) substrate as Y-type films by the vertical dipping method. In the absorption spectra, the λ$\_$max/ of P3HT-AA LB films and of spin-coating films showed about at 510, 545 and 590 nm corresponding to 2.43, 2.28, 2.10eV. And we observed that the turn-on voltage of devices deposited by LB method(10V) was higher than that of spin-coating method(8.5V) in voltage-current-luminance characteristic. In the logV-logJ characteristics of ITO/P3HT-AA LB/Al device, we confirmed that El device fabricated by LB method follows three conduction mechanisms: ohmic, space-charge-limited current(SCLC) conduction and trapped-carrier-limited space-charge current(TCLC) conduction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.460-463
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• 2000

The current-voltage characteristics of the sandwich system at different annealing temperatures and different bias voltages have been studied. In order to prepare the Al/V$O_X$/Al sandwich devices structure, thin films of vanadium oxide(V$O_X$) was deposited by r.f. magnetron sputtering from $V_2$$O_5$ target in 10% gas mixture of argon and oxygen, and annealed during lhour at different temperatures in vacuum. Crystall structure, surface morphology, and thickness of films were characterized through XRD, SEM and I-V characteristics were measured by electrometer. The films prepared below 20$0^{\circ}C$ were amorphous, and those prepared above 300 $^{\circ}C$were polycrystalline. At low fields electron injected to conduction band of vanadium oxide and formed space charge, current was limited by trap. Conduction mechanism at mid fields due to Schottky emission, while at high fields it changed to Fowler-Nordheim tunneling effects.

• Journal of the Korean Vacuum Society
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• v.9 no.3
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• pp.242-248
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• 2000

BST thin films were prepared with various deposition conditions by rf-magnetron sputtering. As substrate temperature increases and Ar/$O_2$ratio decreases, the electrical properties of the BST films improve. The conventional Schottky model and modified-Schottky model were introduced in order to investigate the leakage-current-conduction mechanisms of the deposited films. It was found that the modified-Schottky model better describes the current-conduction mechanism in the BST films than the conventional Schottky model. From the modified-Schottky model, optical dielectric constant ($\varepsilon$), electronic drift mobility ($\mu$), and barrier height $({\phi}_b)are calculated as $\varepsilon$=4.9, $\mu$=0.019 $\textrm{cm}^2$/V-s, and ${\phi}_b=0.79 eV.

• Journal of Power Electronics
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• v.14 no.5
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• pp.890-898
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• 2014

Critical conduction mode boost power factor correction converters operating at the boundary of continuous conduction mode and discontinuous conduction mode have been widely used for power applications lower than 300W. This paper proposes an enhanced variable on-time control method for the critical conduction mode boost PFC converter to improve the total harmonic distortion characteristic. The inductor current, which varies according to the input voltage, is analyzed in detail and the optimal on-time is obtained to minimize the total harmonic distortion with a digital controller using a TMS320F28335. The switch on-time varies according to the input voltage based on the computed optimal on-time. The performance of the proposed control method is verified by a 100W PFC converter. It is shown that the optimized on-time reduces the total harmonic distortion about 52% (from 10.48% to 5.5%) at 220V when compared to the variable on-time control method.

• Journal of Power Electronics
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• v.15 no.5
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• pp.1168-1177
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• 2015

This paper presents a scheme to improve the line current distortion of power factor corrector (PFC) topology at the zero crossing point using a predictive control algorithm in both the continuous conduction mode (CCM) and discontinuous conduction mode (DCM). The line current in single-phase PFC topology is distorted at the zero crossing point of the input AC voltage because of the characteristic of the general proportional integral (PI) current controller. This distortion degrades the line current quality, such as the total harmonic distortion (THD) and the power factor (PF). Given the optimal duty cycle calculated by estimating the next state current in both the CCM and DCM, the proposed predictive control algorithm has a fast dynamic response and accuracy unlike the conventional PI current control method. These advantages of the proposed algorithm lower the line current distortion of PFC topology. The proposed method is verified through PSIM simulations and experimental results with 1.5 kW bridgeless PFC (BLPFC) topology.

• Journal of Power Electronics
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• v.11 no.1
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• pp.97-104
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• 2011

This paper proposes a new alternating current driving method for highly capacitive loads such as plasma display panels or piezoelectric actuators, etc. In the proposed scheme, a current balance transformer, which has two windings with the same turn-ratio, provides not only a resonance inductance for energy recovery but also a current balance among all of the switching devices of the driver for current stress reduction. The smaller conduction loss than conventional circuits occurs due to the dual conduction paths which are parallel each other in the current balance transformer. Also, the leakage inductances of the transformer are utilized as resonant inductors for energy recovery by the series resonance to the capacitive load. Furthermore, the resonance contributes to the small switching losses of the switching devices by soft-switching operation. To confirm the validity of the proposed circuit, prototype hardware with a 12-inch mercury-free flat fluorescent lamp is implemented. The experimental results are compared with a conventional energy-recovery circuit from the perspective of luminance performances.