• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.131-131
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• 2010

We compared the electrical, optical, structural, and interface properties of indium zinc oxide (IZO)-Ag-IZO and IZO-Au-IZO multilayer electrodes deposited by linear facing target sputtering system at room temperature for organic photovoltaics. The IZO-Ag-IZO and IZO-Au-IZO multilayer electrodes show a significant reduction in their sheet resistance (4.15 and 5.49 Ohm/square) and resistivity ($3.9{\times}10^{-5}$ and $5.5{\times}10^{-5}$Ohm-cm) with increasing thickness of the Ag and Au layers, respectively. In spite of its similar electrical properties, the optical transmittance of the IZO-Ag-IZO electrode is much higher than that of the IZO-Au-IZO electrode, due to the more effective antireflection effect of Ag than Au in the visible region. In addition, the Auger electron spectroscopy depth profile results for the IZO/Ag/IZO and IZO/Au/IZO multilayer electrodes showed no interfacial reaction between the IZO layer and Ag or Au layer, due to the low preparation temperature. To investigate in detail the Ag and Au structures on the bottom IZO electrode with increasing thickness, a synchrotron x-ray scattering examination was employed. Moreover, the OSC fabricated on the IZO-Ag-IZO electrode shows a higher power conversion efficiency (3.05%) than the OSC prepared on the IZO-Au-IZO electrode (2.66%), due to its high optical transmittance in the wavelength range of 400-600 nm, which is the absorption wavelength of the P3HT:PCBM active layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.292.2-292.2
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• 2013

Graphene, a two-dimensional graphite material consisting of sp2-hybridized carbons. The properties of graphene such as extremely high carrier mobility, high thermal conductivity, low resistivity, large specific make it a promising materail of divices and material. Typically, poly (methyl methacrylate) (PMMA) is used when graphene transfer to other substrates. To remove PMMA on graphene, people used to dip the graphene into the acetone. However, it is known that the remove of PMMA on the graphene is difficult to completely using the acetone. Therefore, to remove the PMMA on the graphene surface, many research groups have employed various methods such as the thermal treatment, photothermal method, and other solvent. Nevertheless, a part of PMMA still remain on graphene surface. Usually, to observe the residual PMMA on graphene surface, topography of graphene surface scanned by atomic force microscopy is used. However, in that case, we can not distinguish PMMA and other particles. In this study, to confirm the residual PMMA on graphene surface, we employed novel measurement technique which is available to distinguish PMMA and other particles by means of photothermal effect.

• Korean Journal of Materials Research
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• v.22 no.10
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• pp.508-512
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• 2012

ZnO thin films were grown on a sapphire substrate by RF magnetron sputtering. The characteristics of the thin films were investigated by ellipsometry, X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL), and Hall effect. The substrate temperature and growth time were kept constant at $200^{\circ}C$ at 30 minutes, respectively. The RF power was varied within the range of 200 to 500 W. ZnO thin films on sapphire substrate were grown with a preferred C-axis orientation along the (0002) plan; X-ray diffraction peak shifted to low angles and PL emission peak was red-shifted with increasing RF power. In addition, the electrical characteristics of the carrier density and mobility decreased and the resistivity increased. In the electrical and optical properties of ZnO thin films under variation of RF power, the crystallinity improved and the roughness increased with increasing RF power due to decreased oxygen vacancies and the presence of excess zinc above the optimal range of RF power. Consequently, the crystallinity of the ZnO thin films grown on sapphire substrate was improved with RF sputtering power; however, excess Zn resulted because of the structural, electrical, and optical properties of the ZnO thin films. Thus, excess RF power will act as a factor that degrades the device characteristics.

• Korean Journal of Materials Research
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• v.18 no.1
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• pp.32-37
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• 2008

The electrical, optical, structural and surface properties of an indium tin oxide (ITO) film grown on a flexible PET substrate using a specially designed roll-to-roll (R2R) sputtering system as a function of the DC power, $Ar/O_2$ flow ratio, and rolling speed is reported. It was observed that both the electrical and optical properties of the ITO film on the PET substrate were critically dependent on the $Ar/O_2$ flow ratio. In addition, x-ray diffraction examination results showed that the structure of the ITO film on the PET substrate was an amorphous structure regardless of the DC power and the $Ar/O_2$ flow ratio due to a low substrate temperature, which was maintained constant by a main cooling drum. Under optimized conditions, ITO film with resistivity of $6.44{\times}10^{-4}{\Omega}-cm$ and transparency of 86% were obtained, even when prepared at room temperature. Furthermore, bending test results exhibited that R2R-grown ITO film had good flexibility which would be applicable to flexible displays and solar cells.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.308-308
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• 2012

Electrodeposition of thermoelectric materials, including binary and ternary compounds, have been attracting attentions, because its many advantages including cost-effectiveness, rapid deposition rate, and ease of control their microstructure and crystallinity by adjusting electrodeposition parameters. In this work, $Bi_xTe_y$ films were potentiostatically electrodeposited using Au/Ni(80/20 nm)/Si substrate as the working electrode in solutions consisting of 10mM $TeO_2$ and 1M $HNO_3$ where $Bi(NO_3)_3$ was varied from 2.5 to 10 mM. Prior to electrodeposition potentiostatically, linear sweep voltammograms (LSV) were acquired with a standard three-electrode cell. The $Bi_xTe_y$ films deposited using the electrolyte containing low Bi ions shows p-type conductivity, which might be attributed by the large incorporation of Te phases. Near stoichiometric $Bi_2Te_3$ thin films were obtained from electrolytes containing 5mM $Bi(NO_3)_3$. This film shows the maximum Seebeck coefficient of $-100.3{\pm}12.7{\mu}V/K$. As the increase of Bi ions in electrolytes decreases the Seebeck coefficient and resistivity. The maximum power factor of $336.2{\mu}W/m{\cdot}K^2$ was obtained from the film deposited using the solution of 7.5mM $Bi(NO_3)_3$.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.145-145
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• 2010

In this paper, we report that the effects of hydrogen doping on the electrical and optical properties of typical transparent conducting oxide films such as ZnO and $SnO_2$ prepared by magnetron sputtering. Recently, density functional theory (DFT) calculations have shown strong evidence that hydrogen acts as a source of n-type conductivity in ZnO. In this work, the beneficial effect of hydrogen incorporation on Ga-doped ZnO thin films was demonstrated. It was found that hydrogen doping results a noticeable improvement of the conductivity mainly due to the increases in carrier concentration. Extent of the improvement was found to be quite dependent on the deposition temperature. A low resistivity of $4.0{\times}10^{-4}\;{\Omega}{\cdot}cm$ was obtained for the film grown at $160^{\circ}C$ with $H_2$ 10% in sputtering gas. However, the beneficial effect of hydrogen doping was not observed for the films deposited at $270^{\circ}C$. Variations of the electrical transport properties upon vacuum annealing showed that the difference is attributed to the thermal stability of interstitial hydrogen atoms in the films. Theoretical calculations also suggested that hydrogen forms a shallow-donor state in $SnO_2$, even though no experimental determination has yet been performed. We prepared undoped $SnO_2$ thin films by RF magnetron sputtering under various hydrogen contents in sputtering ambient and then exposed them to H-plasma. Our results clearly showed that the hydrogen incorporation in $SnO_2$ leads to the increase in carrier concentration. Our experimental observation supports the fact that hydrogen acting as a shallow donor seems to be a general feature of the TCOs.

• Geophysics and Geophysical Exploration
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• v.19 no.4
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• pp.200-211
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• 2016

To support cross potential array and direct potential array, the array for leakage detection of all kinds of water facilities is proposed and it is named as the D-Lux array. The D-Lux array data are arranged to a coloured matrix and it is called the D-Lux view. Low potential difference of anomalous zone shown in D-Lux view implies the indication of leakage zone. Furthermore, for an intuitive interpretation of D-Lux array, equipotential distribution map is made by using D-Lux and direct potential array data. Equipotential distribution map makes us possible to predict import point, export point and the path of water leakage that we could have not anticipated in D-Lux view and the graphs. The water tank experiment and numerical analysis were carried out as preparatory experiment and the field explorations were conducted at a concrete weir and a fill dam. As a result, effective and specific detection of leakage path was possible for the concrete weir and the fill dam.

• Korean Journal of Materials Research
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• v.31 no.3
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• pp.150-155
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• 2021

Zinc oxide (ZnO) based transparent conducting oxides (TCO) thin films, are used in many applications such as solar cells, flat panel displays, and LEDs due to their wide bandgap nature and excellent electrical properties. In the present work, fluorine and aluminium-doped ZnO targets are prepared and thin films are deposited on soda-lime glass substrate using a RF magnetron sputtering unit. The aluminium concentration is fixed at 2 wt%, and the fluorine concentration is adjusted between 0 to 2.0 wt% with five different concentrations, namely, Al2ZnO98(AZO), F0.5AZO97.5(FAZO1), F1AZO97(FAZO2), F1.5AZO96.5(FAZO3), and F2AZO96(FAZO4). Thin films are deposited with an RF power of 40 W and working pressure of 5 m Torr at 270 ℃. The morphological analysis performed for the thin film reveals that surface roughness decreases in FAZO1 and FAZO2 samples when doped with a small amount of fluorine. Further, optical and electrical properties measured for FAZO1 sample show average optical transmissions of over 89 % in the visible region and 82.5 % in the infrared region, followed by low resistivity and sheet resistance of 3.59 × 10-4 Ωcm and 5.52 Ω/sq, respectively. In future, these thin films with excellent optoelectronic properties can be used for thin-film solar cell and other optoelectronics applications.

• Journal of Powder Materials
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• v.29 no.3
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• pp.240-246
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• 2022

Novel Ni- and Fe-based alloys are developed to impart improved mechanical properties and corrosion resistance. The designed alloys are manufactured as a powder and deposited on a steel substrate using a high-velocity oxygen-fuel process. The coating layer demonstrates good corrosion resistance, and the thus-formed passive film is beneficial because of the Cr contained in the alloy system. Furthermore, during low-temperature heat treatment, factors that deteriorate the properties and which may arise during high-temperature heat treatment, are avoided. For the heattreated coating layers, the hardness increases by up to 32% and the corrosion resistance improves. The influence of the heat treatment is investigated through various methods and is considered to enhance the mechanical properties and corrosion resistance of the coating layer.

• The Journal of Engineering Geology
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• v.32 no.4
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• pp.525-534
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• 2022

This investigation used two different geophysical logging techniques to confirm the depth to which a sheet pile was driven. Depth was estimated through analysis of the movement speed and three-component movement directions of a P-wave transmitted through the ground. It was also estimated by pole-pole and pole-dipole methods using electrical data logging to measure apparent resistivity. The two methods' respective results were 9.0 m (±1.5 m) and 7.5 m. As field ground conditions will include mixtures of various materials, electrical data logging is judged to be suitable for assessing depth due to its low signal-to-noise ratio.