• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05a
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• pp.53-56
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• 2004

The a-Si:H TFT using ferroelectric of SrTi $O_3$as a gate insulator is fabricated on glass. Dielectric characteristics of ferroelectric are superior to $SiO_2$and S $i_3$ $N_4$. Ferroelctric increases on-current, decreases thresh old voltage of TFT and also improves breakdown characteristics. The a-SiN:H has optical band gap of 2.61 eV, refractive index of 1.8~2.0 and resistivity of 10$^{13}$ - 10$^{15}$ $\Omega$cm, respectively. Insulating characteristics of ferroelectrics are excellent because dielectric constant of ferroelectric is about 60~100 and breakdown strength is over 1MV/cm. TFT using ferroelectric has channel length of 8~20${\mu}{\textrm}{m}$ and channel width of 80~200${\mu}{\textrm}{m}$. And it shows that drain current is 3.4$mutextrm{A}$ at 20 gate voltage, $I_{on}$ / $I_{off}$ is a ratio of 10$^{5}$ - 10$^{8}$ and $V_{th}$ is 4~5 volts, respectively. In the case of TFT without ferroelectric, it indicates that the drain current is 1.5 $mutextrm{A}$ at 20 gate voltage and $V_{th}$ is 5~6 volts. With the improvement of the ferroelectric thin film properties, the performance of TFT using this ferroelectric has advanced as a gate insulator fabrication technology is realized.zed.d.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.878-881
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• 2006

In this paper, the luminance and resistance from different electrode materials of external electrode fluorescent lamp are measured and analyzed. New materials and process technology of external electrode are very important for the developed characteristics in lamp fabrication. In this experiments, three different types for the forming of external electrode are Cu and Al taping, silver paste, Ni and Cu electrode-less plating methods. In the measurements of luminance, the results of brightness by Ni and Au plating methods for the external electrode on lamp glass are presented and also compared with the results by the methods using different electrode materials. The measured resistance values of Ni and Au plating process showed a little bit higher than that of silver paste process in spite of developed results of brightness. But the Ni and Ni/Au plating processes are demonstrated best results and are also showed a little bit different brightness due to different previous sulfate etching treatments.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.414-415
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• 2005

A solar cell is an element to transform the solar light energy into the electric energy in a moment. The single crystal element of high quality on which many studies were conducted in the past has a high efficiency of energy transformation, but its price competitiveness is so poor that it has failed to be popularized However, recently, in terms of an environment-friendly alternative energy, studies on applicability of the polycrystal solar cell have been actively under way. Among subject substances for such solar cell, $CuInSe_2$ has several good physical properties so that the greatest attention is paid to it as an optical absorption layer material for a low-cost solar cell of high efficiency. In order to manufacture the $CuInSe_2$ compound thin film, the unit element was deposited by using the sputtering method and the evaporation method and the heat treatment process was used in an electric furnace. Thereby, we intended to get a single-phase $CuInSe_2$ compound thin film.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.86-86
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• 2010

Micro- and nanoscale texturing and control of surface energy have been considered for superhydrophobicity on polymer and silicon. However these surfaces have been reported to be difficult to meet the robustness and transparency requirements for further applications, from self cleaning windows to biochip technology. Here we provided a novel method to fabricate a nearly superhydrophobic soda-lime glass using two-step method. The first step involved wet etching process to fabricate micro-sale patterns on soda-lime glass. The second step involved application of $SiO_x$-incorporated DLC to generate high intrinsic contact angle on the surface using chemical vapor deposition (CVD) process. To investigate the effect of surface roughness, we used both positive and negative micro-scale patterns on soda-limeglass, which is relatively hard for surface texturing in comparison to quartz or Pyrex glasses due to the presence of impurities, but cheaper. For all samples we tested the static wetting angle and transparency before and after 100 cycles of wear test using woolen steel. The surface morphology is observed using optical and scanning electron microscope (SEM). The results shows that negative patterns had a greater wear resistance while the hydrophobicity was best achieved using positive patterns having static contact angle up to 140 deg. with about 80% transparency. The overall experiment shows that positive patterns at etching time of 1 min shows the optimum transparency and hydrophobicity. The optimization of micro-scale pattern to achieve a robust, transparent, superhydrophobic soda-lime glass will be further investigated in the future works.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.252.2-252.2
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• 2013

ZnO nanostructures have a lot of interest for decades due to its varied applications such as light-emitting devices, power generators, solar cells, and sensing devices etc. To get the high performance of these devices, the factors of nanostructure geometry, spacing, and alignment are important. So, Patterning of vertically- aligned ZnO nanowires are currently attractive. However, many of ZnO nanowire or nanorod fabrication methods are needs high temperature, such vapor phase transport process, metal-organic chemical vapor deposition (MOCVD), metal-organic vapor phase epitaxy, thermal evaporation, pulse laser deposition and thermal chemical vapor deposition. While hydrothermal process has great advantages-low temperature (less than $100^{\circ}C$), simple steps, short time consuming, without catalyst, and relatively ease to control than as mentioned various methods. In this work, we investigate the dependence of ZnO nanowire alignment and morphology on si substrate using of nanosphere template with various precursor concentration and components via hydrothermal process. The brief experimental scheme is as follow. First synthesized ZnO seed solution was spun coated on to cleaned Si substrate, and then annealed $350^{\circ}C$ for 1h in the furnace. Second, 200nm sized close-packed nanospheres were formed on the seed layer-coated substrate by using of gas-liquid-solid interfacial self-assembly method and drying in vaccum desicator for about a day to enhance the adhesion between seed layer and nanospheres. After that, zinc oxide nanowires were synthesized using a low temperature hydrothermal method based on alkali solution. The specimens were immersed upside down in the autoclave bath to prevent some precipitates which formed and covered on the surface. The hydrothermal conditions such as growth temperature, growth time, solution concentration, and additives are variously performed to optimize the morphologies of nanowire. To characterize the crystal structure of seed layer and nanowires, morphology, and optical properties, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and photoluminescence (PL) studies were investigated.

• Korean Journal of Materials Research
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• v.16 no.10
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• pp.629-632
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• 2006

Electrical characteristics of Pt/Ti/Pt/Au and Pd/Zn/Pd/Au contacts to p-type InGaAs grown on an InP substrate have been characterized as a function of the doping concentration and the annealing temperature. The Pt/Ti/Pt/Au contacts produced the specific contact resistance as low as $2.3{\times}10^{-6}{\Omega}{\cdot}cm^2$, when heat-treated at an annealing temperature of $400^{\circ}C$. Comparison of the Pt/Ti/Pt/Au and Ti/Pt/Au contacts showed that the first Pt layer plays an important role in reducing the contact resistivity probably by lowering energy barrier at the metal-semiconductor interface. For the Pd/Zn/Pd/Au contacts, the contact resistivity remained virtually unchanged with increasing annealing temperature. The specific contact resistivity as low as $4.7{\times}10^{-6}{\Omega}{\cdot}cm^2$ was obtained. The results indicate that the Pt/Ti/Pt/Au and Pd/Zn/Pd/Au schemes could be potentially important for the fabrication of InP-based optoelectronic devices, such as photodetector and optical modulator.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.166-166
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• 2010

Recently, TFTs based on amorphous oxide semiconductors (AOSs) such as ZnO, InZnO, ZnSnO, GaZnO, TiOx, InGaZnO(IGZO), SnGaZnO, etc. have been attracting a grate deal of attention as potential alternatives to existing TFT technology to meet emerging technological demands where Si-based or organic electronics cannot provide a solution. Since, in 2003, Masuda et al. and Nomura et al. have reported on transparent TFTs using ZnO and IGZO as active layers, respectively, much efforts have been devoted to develop oxide TFTs using aforementioned amorphous oxide semiconductors as their active layers. In this thesis, I report on the performance of thin-film transistors using amorphous indium gallium zinc oxides for an active channel layer at room temperature. $SiO_2$ was employed as the gate dielectric oxide. The amorphous indium gallium zinc oxides were deposited by RF magnetron sputtering. The carrier concentration of amorphous indium gallium zinc oxide was controlled by oxygen pressure in the sputtering ambient. Devices are realized that display a threshold voltage of 1.5V and an on/off ration of > $10^9$ operated as an n-type enhancement mode with saturation mobility with $9.06\;cm^2/V{\cdot}s$. The devices show optical transmittance above 80% in the visible range. In conclusion, the fabrication and characterization of thin-film transistors using amorphous indium gallium zinc oxides for an active channel layer were reported. The operation of the devices was an n-type enhancement mode with good saturation characteristics.

• Polymer(Korea)
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• v.34 no.4
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• pp.376-380
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• 2010

Donor-$\pi$-acceptor (D-$\pi$-A) type chromophore-based polymers were newly synthesized. These polymers exhibited absorption peak due to intramolecular charge transfer (ICT) in a visible range as well as absorption peak due to carbonyl group in both solution and film state by measuring UV visible spectra. The addition of $Eu^{3+}$ ion into the polymers induced red-shift in absorption due to ICT and the color changes from yellow to red in the solution and film were observed by naked eyes. The contents of crosslinking agent influenced the features and solubility of the polymers. In addition, the contents of crosslinking agent and the $Eu^{3+}$ ion addition improved film-forming ability.

• Korean Journal of Optics and Photonics
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• v.25 no.2
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• pp.102-107
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• 2014

In this paper the spectra of correlated color temperature (CCT) tunable white light-emitting diode (LED) luminaires, consisting of commercial red, green, blue, and amber LED chips, were optimized to increase color rendering index (CRI), and a special CRI of R9 for deep red color was obtained. To improve the design's accuracy, measured LED spectra were used instead of mathematically modeled ones. Real CCT tunable LED luminaires with CRIs of 87-90 and R9s of 34-93 were fabricated and demonstrated at CCTs of 3000-6000 K.

• Nano
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• v.13 no.12
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• pp.1850146.1-1850146.9
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• 2018

The rapid development of smart textiles requires the large-scale fabrication of conductive fibers. In this study, we develop a simple, scalable and low-cost capillary-driven self-assembly method to prepare conductive fibers with uniform morphology, high conductivity and good mechanical strength. Fiber-shaped flexible and stretchable conductors are obtained by coating highly conductive and flexible silver nanowires (Ag NWs) on the surfaces of yarn and PDMS fibers through evaporation-induced flow and capillary-driven self-assembly, which is proven by the in situ optical microscopic observation. The density of Ag NWs and linear resistance of the conductive fibers could be regulated by tuning the assembly cycles. A linear resistance of $1.4{\Omega}/cm$ could be achieved for the Ag NWs-coated nylon, which increases only 8% after 200 bending cycle, demonstrating high flexibility and mechanical stability. The flexible and stretchable conductive fibers have great potential for the application in wearable devices.