• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.2
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• pp.107-113
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• 2009

In order to improve air stability, we proposed a new active layer of an organic TFT by synthesizing P3HT/POSS conjugated polymer. P3HT/POSS OTFTs with the various P3HT/POSS volume ratios were fabricated and characterized. With the P3HT/POSS volume ratio of 1:1, we achieved the field-effect mobilities of ${\sim}1.19{\times}10^{-3}\;cm^2/v{\cdot}sec$ in the saturation region and the current on/off ratio of ${\sim}2.51{\times}10^2$. The resulting current on-off ratio was much higher than that of the P3HT-based OTFTs and resulted from the dramatic decrease of the off-current. Since the off-current can be reduced by preventing oxygen in atmosphere from doping the P3HT/POSS active layers, this new active layer shows its ability to avoid oxygen doping in atmosphere. Therefore, the improvement of the air stability can be achieved by employing the P3HT/POSS active layers.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.3
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• pp.229-233
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• 2019

Pure $BiFeO_3$ (BFO) and (Eu, V) co-doped $Bi_{0.9}Eu_{0.1}Fe_{0.975}V_{0.025}O_{3+{\delta}}$ (BEFVO) thin films were deposited on $Pt(111)/Ti/SiO_2/Si(100)$ substrates by chemical solution deposition. The effects of co-doping were observed by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy (SEM). The electrical properties of the BEFVO thin film were improved as compared to those of the pure BFO thin film. The remnant polarization ($2P_r$) of the BEFVO thin film was approximately $26{\mu}C/cm^2$ at a maximum electric field of 1,190 kV/cm with a frequency of 1 kHz. The leakage current density of the co-doped BEFVO thin film ($4.81{\times}10^{-5}A/cm^2$ at 100 kV/cm) was two orders of magnitude lower than of that of the pure BFO thin film.

• Journal of Korean Vacuum Science & Technology
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• v.6 no.2
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• pp.58-61
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• 2002

Photoluminescence up-conversion in semiconductor heterostructures is a phenomenon in which luminescence occurs at energies higher than that of the excitation photons. It has been observed in many semiconductor heterostructure systems, including InP/AnALAs, CdTe/CdMgTe, GaAs/ordered-(Al)GalnP, GaAs/AIGaAs, and InAs/GaAs. In this wort, GaAs/AIGaAs heterostructures are used as a model system to study the mechanism of the up-conversion process. This system is ideal for testing different models because the band offsets are quite well documented. Different heterostructures are designed to study the effect of disorder on the up-converted luminescence efficiency. In order to study the roles of different types of carriers, the effect of doping was investigated. It was found that the up-converted luminescence is significantly enhanced by p-type doping of the higher-band-gap material.

• Transactions on Electrical and Electronic Materials
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• v.16 no.2
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• pp.78-81
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• 2015

Pure ZnO and ZnO nanowires doped with 3 wt.% Ga (‘3GZO’) were grown by pulsed laser deposition in a furnace system. The doping of Ga in ZnO nanowires was analyzed by observing the optical and chemical properties of the doped nanowires. The diameter and length of nanowires were under 200 nm and several ${\mu}m$, respectively. Changes of significant resistance were observed and the sensitivities of ZnO and 3GZO nanowires were compared. The sensitivities of ZnO and 3GZO nanowire sensors measured at 300℃ for 1 ppm of ethanol gas were 97% and 48%, respectively.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.601-604
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• 1998

NOX detecting gas sensors using TiO2 doped tungsten oxide semiconductor were prepared and their electrical and sensing characteristics have been investigated. In normal air condition, the sensors of WO3, TiO2 doped WO3 show grain boundary heights of 0.34 eV, 0.25 eV, respectively. The grain boundary barrier energy variation was increased by doping TiO2 into large variation of resistance to NOX gases. And doping the TiO2 4 wt.%, the particle size of WO3 polycrystal films showed higher sensitivity and better sorption characteristics to NOX gas than the pure WO3 films material in air at operating temperature of $350^{\circ}C.$ The TiO2 doped WO3 semiconductor gas sensor shows nano-sized particle size and good sensitivity to sub-ppm concentration of NOX.

• Transactions on Electrical and Electronic Materials
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• v.12 no.5
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• pp.204-208
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• 2011

In this paper, the design area of a fabricated solar cell has been analyzed with respect to its charge density. The mathematical calculation used for charge-density derivation was obtained from the 2001 version of a MATHCAD program. The parameter range for the calculations was ${\pm}1{\times}10^{17}cm^{-3}$, which is in the normal parameter range for n-type doping impurities ($7.0{\times}10^{17}cm^{-3}$) and also for p-type impurities ($4.0{\times}10^{17}cm^{-3}$). Therefore, it can be said that the fabricated solar-cell design area has a direct effect on charge-density changes.

• Transactions on Electrical and Electronic Materials
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• v.17 no.2
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• pp.69-78
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• 2016

Liquid crystals are important materials because of their applications in display technology and many other scientific applications. Different mixtures of liquid crystals and their doped samples have gained interest because a single liquid crystal compound cannot fulfill all the required parameters for the display application. The doping can be accomplished with dyes, polymers, or composite nanoparticles among other substance. The addition of nanoparticles can modify the physical properties of the host liquid crystal and enhances the performance of electro-optical devices. The present study is focused on investigations of possible changes in dielectric and electro optical properties of liquid crystals caused by doping with ceramic nanoparticles. Including smaller nanoparticles were found to be better candidates for use in suppressing the unwanted ion effects in liquid crystal displays.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.1
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• pp.19-22
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• 1999

N-doped and low-hydrogenated DLC thin films were coated on the Mo-tip FEAs in order to improve the field emission performance and their electrical properties were evaluated. The fabricated devices showed improved field emission performance in terms of turn-on voltage, emission current and current fluctuation. This result might be caused both by the shift of Fermi level toward conduction band by N-doping and by the inherent stability of DLC material. Furthermore, the transconductance of the DLC-coated Mo-tip FEA and electrical conductivity and optical band-gap of the deposited DLC films were investigated.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.181-182
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• 2011

Phase-change materials can be cycled by exposure to laser beam, and as a function of the pulse intensity and duration, the laser beam triggers the switching from crystalline to amorphous phase and back. In other to progress better crystallization transition and amorphization long phase-transformation data of phase-change memory (PRAM), we investigated about the effect of Sb doping and Ag ions percolating into Ge-Se-Te phase-change material. Doped Sb concentrations was determined each of 10, 20 and 30 wt%. As the Sb-doping concentration was increased, the resistivity decreased and the crystallization temperature increased. Ionization of Ag was progressed by DPSS laser (532 nm) for 1 hour. The resistivity was more decreased and the crystallization temperature was more increased in case of adding Ag layer under Sb-(Ge-Se-Te) thin film. At the every condition of thin films included Ag layer more stable states were indicated compare with just Sb-doped Ge-Se-Te thin films.

• Bulletin of the Korean Chemical Society
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• v.23 no.8
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• pp.1144-1148
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• 2002

We prepared the polyaniline (Pani) film and powder by chemical polymerization and doping with different dopants and also investigated the capability of Li//polyaniline cells after assembling. The oxidation/reduction potentials and electrochemical reaction of Li//polyaniline cells were tested by cyclic voltammetry technique. The Li//Pani-HCl cells with 10% and 20% conductors show a little larger specific discharge capacities than that without conductor. The highest discharge capacity of almost 50 mAh/g at 100th cycle is also achieved. However, Li//Pani-LiPF6 with 20% conductor shows a remarkable performance of ~90 mAh/g at 100th cycle. This is feasible value for using as the positive electrode material of lithium ion secondary batteries. It is also proved that the powder type electrode of Pani is better to use than the film type one to improve the specific discharge capacity and its stability with cycle.