• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.8
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• pp.591-596
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• 2013

Indium Zinc Tin Oxide (IZTO) thin films were developed as an alternative to Indium Tin Oxide (ITO) thin films. ITO material which has been acknowledged with its low resistivity and optical transparency of 85-90% has been used as major transparent conducting oxide (TCO) materials. However, due to the limited source, high price, and instability problems at high temperature of indium, many researches has been focused on indium-saving TCO materials. Mason Group of Northwestern University was reported to expand the solubility limit up to 40% by co-doping with 1:1 ratio of $Zn^{+2}$ and $Sn^{+4}$ ions. In this study, the properties of IZTO thin films corresponding to Zn/Sn different ratio were investigated. In addition, the effect of substrate temperature variable to the structural, optical and electrical properties of IZTO thin films was investigated.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.62.1-62.1
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• 2011

현재 상용화된 LED 또는 태양전지 등의 투명전극(TCO, transparent couducting oxide)재료로 높은 전기전도도와 광투과도를 갖는 ITO (Indium Tin Oxide)가 많이 채택되고 있다. 그러나 이에 사용되는 Indium의 단가가 높다는 문제점이 있어 이를 대체하기 위한 물질의 연구가 많이 이루어지고 있다. 특히 Aluminum을 doping한 ZnO (AZO)는 우수한 전기적, 광학적 특성 등으로 인해 ITO를 대체할 차세대 TCO 물질로 각광받고 있다. 본 연구에서는 sol-gel법을 및 direct patterning법을 이용하여 moth-eye 패턴을 포함하는 AZO 박막을 제작하였다. AZO sol을 제작하기 위하여 2-methoxyethanol, zinc acetate dihydrate 및 doping source로 aluminum nitrate nonahydrate를 사용하였다. 또한 광추출 향상 효과를 갖는 moth-eye 구조의 master stamp를 Polydimethyl siloxane(PDMS)를 이용하여 역상 moth-eye 구조의 mold를 복제하였으며, 이 복제된 mold와 제작된 AZO sol을 이용한 direct patterning법을 통해 나노급 moth-eye 구조를 갖는 AZO 투명전극층을 형성하였다. 제작된 moth-eye 구조를 갖는 AZO 투명전극층의 전기적 특성 평가를 위해, 4-point probe 측정 및 Hall measurement를 시행하였으며, 광학적 특성을 확인하기 위하여 UV-Visable spectrometer를 이용하여 투과도를 측정하였다. 본 연구를 통해 현재 상용화된 광전자 소자에 사용되고 있는 ITO 투명전극을 대체할 차세대 투명전극으로써 AZO 박막의 가능성을 확인하였다.

• Laser Solutions
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• v.11 no.4
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• pp.21-28
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• 2008

Remote Laser welding technology for manufacturing automotive body is studied. Laser welding and industrial robot systems are used for the robot based laser welding system. The laser system is used 1.6kW Fiber laser(YLR-1600) of IPG. The robot system is used HX130-02 of Hyundai Heavy Industry(payload : 130kg). The robot based laser welding system is equipped with laser scanner system for remote laser welding. The welding joints of steel plate and steel plate coated with zinc are butt and lapped joints. The quality test of the laser welding are through the observation the shape of bead on plate and cross-section of welding part. During past three years the laser system, 4kW Nd:YAG laser (HL4006D) of Trumpf was used and the robot system, IRB6400R of ABB (payload:120kg) was used. The new laser source, robot and laser scanner system are used to increase the processing speed and to improve the process efficiency. This paper introduces the robot based remote laser welding system to resolve the limited welding speed and accuracy of the conventional laser welding system.

• Journal of radiological science and technology
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• v.44 no.5
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• pp.459-464
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• 2021

The detector performance is important role in acquiring the gamma rays from patients. Among parameters of detector performances, there is density, which relates to respond to gamma rays. Therefore, we confirm the detection efficiency according to various detector materials based on the density parameter using GATE (geant4 application for emission tomography) simulation tool. The NaI (density: 3.67 g/cm³), CZT (Cadimium Zinc Telluride) (density: 5.80 g/cm³), CdTe (Cadmium Telluride) (5.85 g/cm³), and GAGG (Gadoinium Aluminum Gallium Garnet) (density g/cm³) were used as detector materials. In addition, the point source and quadrant bar phantom, which is modeled for 0.5, 1.0, 1.5, and 2.0 mm thicknesses, were modeled to confirm the quatitative analysis using sensitivity (cps/MBq) and the full width at half maximum (FWHM, mm) at the 2.0 mm bar thickness containing visual evaluation. Based on the results, the sensitivity for NaI, CZT, CdTe, and GAGG detector materials were 0.12, 0.15, 0.16, and 0.18 cps/MBq. In addition, the FWHM for quadrant bar phantom in the 2.0 mm bar thickness is 3.72, 3.69, 3.70, and 3.73 mm for NaI, CZT, CdTe, and GAGG materials, respectively. Compared with performance of detector materials according to density, the high density can improve detection efficiency in terms of sensitivity and mean count. Among these detector materials, the GAGG material is efficient for detection of gamma rays.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.341-341
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• 2012

Recently, oxide semi-conductor materials have been investigated as promising candidates replacing a-Si:H and poly-Si semiconductor because they have some advantages of a room-temperature process, low-cost, high performance and various applications in flexible and transparent electronics. Particularly, amorphous indium-gallium-zinc-oxide (a-IGZO) is an interesting semiconductor material for use in flexible thin film transistor (TFT) fabrication due to the high carrier mobility and low deposition temperatures. In this work, we demonstrated improvement of flexibility in IGZO TFTs, which were fabricated on polyimide (PI) substrate. At first, a thin poly-4vinyl phenol (PVP) layer was spin coated on PI substrate for making a smooth surface up to 0.3 nm, which was required to form high quality active layer. Then, Ni gate electrode of 100 nm was deposited on the bare PVP layer by e-beam evaporator using a shadow mask. The PVP and $Al_2O_3$ layers with different thicknesses were used for organic/inorganic multi gate dielectric, which were formed by spin coater and atomic layer deposition (ALD), respectively, at $200^{\circ}C$. 70 nm IGZO semiconductor layer and 70 nm Al source/drain electrodes were respectively deposited by RF magnetron sputter and thermal evaporator using shadow masks. Then, IGZO layer was annealed on a hotplate at $200^{\circ}C$ for 1 hour. Standard electrical characteristics of transistors were measured by a semiconductor parameter analyzer at room temperature in the dark and performance of devices then was also evaluated under static and dynamic mechanical deformation. The IGZO TFTs incorporating hybrid gate dielectrics showed a high flexibility compared to the device with single structural gate dielectrics. The effects of mechanical deformation on the TFT characteristics will be discussed in detail.

• Journal of Powder Materials
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• v.26 no.5
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• pp.375-382
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• 2019

Homogeneous multicomponent indium gallium zinc oxide (IGZO) ceramics for transparent electrode targets are prepared from the oxides and nitrates as the source materials, and their properties are characterized. The selected compositions were $In_2O_3:Ga_2O_3:ZnO$ = 1:1:2, 1:1:6, and 1:1:12 in mole ratio based on oxide. As revealed by X-ray diffraction analysis, calcination of the selected oxide or nitrides at $1200^{\circ}C$ results in the formation of $InGaZnO_4$, $InGaZn_3O_6$, and $InGaZn_5O_8$ phases. The 1:1:2, 1:1:6, and 1:1:12 oxide samples pressed in the form of discs exhibit relative densities of 96.9, 93.2, and 84.1%, respectively, after sintering at $1450^{\circ}C$ for 12 h. The $InGaZn_3O_6$ ceramics prepared from the oxide or nitrate batches comprise large grains and exhibit homogeneous elemental distribution. Under optimized conditions, IGZO multicomponent ceramics with controlled phases, high densities, and homogeneous microstructures (grain and elemental distribution) are obtained.

• Korean Journal of Materials Research
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• v.31 no.9
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• pp.481-487
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• 2021

ZnO particles are successfully synthesized at 150 ℃ for 30 min using zinc acetate as the Zn source and 1,4-butanediol as solvent using a relatively facile and convenient glycol process. The effect of ammonium hydroxide amounts on the growth behavior and the morphological evolution of ZnO particles are investigated. The prepared ZnO nanoparticle with hexagonal structure exhibits a quasi-spherical shape with an average crystallite size of approximately 30 nm. It is also demonstrated that the morphology of ZnO particles can be controlled by 1,4-butanediol with an additive of ammonium hydroxide. The morphologies of ZnO particles are changed sequentially from a quasi-spherical shape to a rod-like shape and a hexagonal rod shape with a truncated pyramidal tip, exhibiting preferential growth along the [001] direction with increasing ammonium hydroxide amounts. It is demonstrated that much higher OH^- amounts can produce a nano-tip shape grown along the [001] direction at the corners and center of the (001) top polar plane, and a flat hexagonal symmetry shape of the bottom polar plane on ZnO hexagonal prisms. The results indicate that the presence of NH⁴⁺ and OH^- ions in the solution greatly affects the growth behaviors of ZnO particles. A sharp near-band-edge (NBE) emission peak centered at 383 nm in the UV region and a weak broad peak in the visible region between 450 nm and 700 nm are shown in the PL spectra of the ZnO synthesized using the glycol process, regardless of adding ammonium hydroxide. Although the broad peak of the deep-level-emission (DLE) increases with the addition of ammonium hydroxide, it is suggested that the prominent NBE emission peaks indicate that ZnO nanoparticles with good crystallization are obtained under these conditions.

• Nutrition Research and Practice
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• v.13 no.5
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• pp.434-443
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• 2019

BACKGROUND/OBJECTIVES: The intake of sugar has increased worldwide, and it is well established that childhood experiences and food preferences affect lifelong eating habits. To discourage sugar intake, nutrition education was imparted, and the effectiveness of the nutrition education program was investigated by considering the nutrient density and major dietary sources of sugar intake. SUBJECTS/METHODS: Twenty four-hour dietary recall and sugar intake frequency of 96 pre-school children (educated n = 47; non-educated n = 49) were collected on 3 consecutive days (1 weekend day, 2 weekdays) after 11 weeks of imparting nutrition education. Dietary intake of nutrients and total sugar were analyzed, and the intake frequency of sugar source foods were identified. All nutrition education programs were focused on a hands-on education program, and consisted of cooking lab, play, activity, animation, and visual materials. The difference between the two groups was verified by the Chi-square test or t-test. All statistical analysis was performed with significance level at P < 0.05. RESULTS: Compared to the non-educated group, the intakes of protein (P < 0.001), fiber (P < 0.01), potassium (P < 0.05), iron (P < 0.05), zinc (P < 0.05), and iodine (P < 0.001) were significantly higher, and the intakes of carbohydrate (P < 0.01) and total sugar (P < 0.05) were significantly lower in the educated group. The cumulative percent of sugar intake of top 20 sugar source foods in the educated group (82.80%) was lower than that of the non-educated group (85.75%). The contribution of beverages on total sugar intake was lower in the educated group. The average frequency of consuming sugary foods was significantly lower in the educated group (P < 0.05). CONCLUSIONS: Our results indicate that nutrition education on discouraging sugar intake is effective in reducing the amount of total sugar consumed, resulting higher nutrient density in the diets of pre-school children.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.479-479
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• 2011

Flexible inverters based on complementary thin-film transistor (CTFTs) are important because they have low power consumption and other advantages over single type TFT inverters. In addition, integrated CTFTs in flexible electronic circuits on low-cost, large area and mechanically flexible substrates have potentials in various applications such as radio-frequency identification tags (RFIDs), sensors, and backplanes for flexible displays. In this work, we introduce flexible complementary inverters using pentacene and amorphous indium gallium zinc oxide (IGZO) for the p-channel and n-channel, respectively. The CTFTs were fabricated on polyimide (PI) substrate. Firstly, a thin poly-4-vinyl phenol (PVP) layer was spin coated on PI substrate to make a smooth surface with rms surface roughness of 0.3 nm, which was required to grow high quality IGZO layers. Then, Ni gate electrode was deposited on the PVP layer by e-beam evaporator. 400-nm-thick PVP and 20-nm-thick ALD Al2O3 dielectric was deposited in sequence as a double gate dielectric layer for high flexibility and low leakage current. Then, IGZO and pentacene semiconductor layers were deposited by rf sputter and thermal evaporator, respectively, using shadow masks. Finally, Al and Au source/drain electrodes of 70 nm were respectively deposited on each semiconductor layer using shadow masks by thermal evaporator. Basic electrical characteristics of individual transistors and the whole CTFTs were measured by a semiconductor parameter analyzer (HP4145B, Agilent Technologies) at room temperature in the dark. Performance of those devices then was measured under static and dynamic mechanical deformation. Effects of cyclic bending were also examined. The voltage transfer characteristics (Vout- Vin) and voltage gain (-dVout/dVin) of flexible inverter circuit were analyzed and the effects of mechanical bending will be discussed in detail.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.480-480
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• 2010

In the present work, we studied effect of the deposition parameters on the structure and properties of ZnO films deposited by DC arc plasmatron. The varied parameters were gas flow rates, precursor composition, substrate temperature and post-deposition annealing temperature. Vapor of Zinc acetylacetone was used as source materials, oxygen was used as working gas and argon was used as the cathode protective gas and a transport gas for the vapor. The plasmatron power was varied in the range of 700-1,500 watts. Flow rate of the gases and substrate temperature rate were varied in the wide range to optimize the properties of the deposited coatings. After deposition films were annealed in the hydrogen atmosphere in the wide range of temperatures. Structure of coatings was investigated using XRD and SEM. Chemical composition was analyzed using x-ray photo-electron spectroscopy. Sheet conductivity was measured by 4-point probe method. Optical properties of the transparent ZnO-based coatings were studied by the spectroscopy. It was shown that deposition by a DC Arc plasmatron can be used for low-cost production of zinc oxide films with good optical and electrical properties. Sheet resistance of 4 Ohms cm was achieved after the deposition and 30 min annealing in the hydrogen at $350^{\circ}C$. Elevation of the substrate temperature during the deposition process up to $350^{\circ}C$ leads to decreasing of the film's resistance due to rearrangement of the crystalline structure.