• Korean Journal of Remote Sensing
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• v.37 no.5_1
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• pp.1187-1198
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• 2021

Sea wind isrecently drawing attraction as one of the sources of renewable energy. Thisstudy describes a new method to produce a 10 m resolution sea wind field using Sentinel-1 images and low-resolution NWP (Numerical Weather Prediction) data with artificial intelligence technique. The experiment for the South East coast in Korea, 2015-2020,showed a 40% decreased MAE (Mean Absolute Error) than the generic CMOD (C-band Model) function, and the CC (correlation coefficient) of our method was 0.901 and 0.826, respectively, for the U and V wind components. We created 10m resolution sea wind maps for the study area, which showed a typical trend of wind distribution and a spatially detailed wind pattern as well. The proposed method can be applied to surveying for wind power and information service for coastal disaster prevention and leisure activities.

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1993-1996
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• 2010

Silver nanoparticles has been prepared by the $\gamma$-irradiation and in situ reduction methods. Based on the Raman spectra, TEM images, X-ray Diffraction (XRD) patterns and UV-vis spectra, the in situ reduction method is more stable and the average size of the silver nanoparticles is also smaller than by the $\gamma$-irradiation reduction method. It is identified that the silver ions interacting with nonbonding electrons of oxygen atom in the carbonyl group of polyvinylpyrrolidone (PVP) by the in situ reduction method. It is also found advantages of the in situ reduction method including no additional reducing agents, without $\gamma$-irradiations treatment and the room temperature treatment suitability.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.221.2-221.2
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• 2015

Graphene is very interesting 2 dimensional material providing unique properties. Especially, graphene has been investigated as a stretchable and transparent conductor due to its high mobility, high optical transmittance, and outstanding mechanical properties. On the contrary, high sheet resistance of extremely thin monolayer graphene limits its application. Artificially stacked multilayer graphene is used to decrease its sheet resistance and has shown improved results. However, stacked multilayer graphene requires repetitive and unnecessary transfer processes. Recently, growth of multilayer graphene has been investigated using a chemical vapor deposition (CVD) method but the layer controlled synthesis of multilayer graphene has shown challenges. In this paper, we demonstrate controlled growth of multilayer graphene using a two-step process with multi heating zone low pressure CVD. The produced graphene samples are characterized by optical microscope (OM) and scanning electron microscopy (SEM). Raman spectroscopy is used to distinguish a number of layers in the multilayer graphene. Its optical and electrical properties are also analyzed by UV-Vis spectrophotometer and probe station, respectively. Atomic resolution images of graphene layers are observed by high resolution transmission electron microscopy (HRTEM).

• Bulletin of the Korean Chemical Society
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• v.25 no.7
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• pp.983-985
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• 2004

PMMA-coated CdS nanorod was prepared by encapsulation of CdS nanorod through the polymerization process of PMMA on the surface of CdS nanorod. PMMA organic nanotube was then obtained from the elimination of the CdS nanorod by the photocorrosion. For the photocorrosion reaction of the CdS nanorod, monochromatic light was irradiated to the oxygen-saturated aqueous methyl viologen solution with PMMAcoated CdS nanorod. Photocorrosion reactions of PMMA-coated CdS nanorod were investigated and characterized by utilizing UV-Vis absorption, X-ray diffraction (XRD) and scanning electron microscopic (SEM) and transmission electron microscopic (TEM) images.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.447-447
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• 2009

In this study, transparent and conductive Al-doped zinc oxide (AZO) films were prepared on Corning glass and silicon wafer substrate by RF magnetron sputtering method using an Al-doped ZnO target (Al: 2 wt.%) at room temperature as the thickness of 150 nm. We investigated the effects of the RF power between 100 Wand 350 W in steps of 50 W on structural, electrical and optical properties of AZO films. Also, we studied the effects of the working pressure (3, 4 and 5 mtorr) on that condition. The thickness and cross-sectional images of films were observed by field emission scanning electron microscopy (FE-SEM) and all of the films were kept to be constant to $150\pm10$ nm on Coming glass and silicon wafer. A grain size was calculated from X-ray diffraction (XRD) on using the Scherrer' equation and their electrical properties investigated hall effect electronic transport measurement system. Moreover, we measured transmittance of AZO films by UV/VIS spectrometer.

• Carbon letters
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• v.12 no.2
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• pp.90-94
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• 2011

We present the effect of a coupling agent on the optoelectrical properties of few-walled carbon nanotube (FWCNT)/epoxy resin hybrid films fabricated on glass substrates. The FWCNT/epoxy resin mixture solution was successfully prepared by the direct mixing of a $HNO_3$-treated FWCNT solution and epoxy resin. FWCNT/binder hybrid films containing different amounts of the coupling agent were then fabricated on UV-ozone-treated glass substrates. To determine the critical binder content ($X_c$), the effects of varying the binder content in the FWCNT/silane hybrid films on their optoelectrical properties were investigated. In this system, the $X_c$ value was approximately 75 wt%. It was found that above $X_c$, the coupling agent effectively decreased the sheet resistance of the films. From microscopy images, it was observed that by adding the coupling agent, more uniform FWCNT/binder films were formed.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1345_1346
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• 2009

In this study, transparent and conductive Al-doped zinc oxide (AZO) films were prepared on glass substrate by RF magnetron sputtering method using an Al-doped ZnO target (Al: 2wt.%) at room temperature as the thickness of 150 nm. We investigated the effects of the RF power between 100~350 W in the steps of 50 W on structural, electrical and optical properties of AZO films. The thickness and cross-sectional images of films were observed by field emission scanning electron microscopy (FE-SEM) and all of the films were kept to be constant about 150 nm on glass substrate. The grain size of AZO films figured out X-ray diffraction (XRD) on using the Scherrer' equation and their electrical properties investigated Hall effect electronic transport measurement system. Moreover, we measured transmittance of AZO films by UV/VIS spectrometer.

• Rapid Communication in Photoscience
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• v.1 no.1
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• pp.13-15
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• 2012

New porous $TiO_2$ nanostructures with shapes of pearl and rice were synthesized by hydrothermal treatment of $TiO_2$-liposome nanocomposites in acid and base solutions, respectively, as identified by scanning electron microscopy (SEM), transmission electron microscopy (TEM) images and large Brunauer-Emmett-Teller (BET) surface areas. The x-ray diffraction (XRD) patterns and selected area electron diffraction proved them to be well-defined anatase crystals. Their UV-visible reflectance absorption spectra were observed to have low band gap energy (3.03 and 3.07 eV, respectively), exhibiting surface absorption band in the visible range from 400 to 600 nm. The degradation of methylene blue (MB) over the $TiO_2$ nanostructures was observed upon visible-light irradiation, which was found to be very efficient as compared with any other conventional visible-light responsive $TiO_2$ nanostructures.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.26.1-26.1
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• 2011

We investigated the atomic layer deposition (ALD) process for nitrogen doped ZnO and the application for n-ZnO : N/p-Si (NW) coaxial hetero-junction photodetectors. ALD ZnO:N was deposited using diethylzinc (DEZ) and diluted $NH_4OH$ at $150^{\circ}C$ of substrate temperature. About 100~300 nm diameter and 5 um length of Si nanowires array were prepared using electroless etching technique in 0.108 g of $AgNO_3$ melted 20 ml HF liquid at $75^{\circ}C$. TEM images showed ZnO were deposited on densely packed SiNW structure achieving extraordinary conformality. When UV (360 nm) light was illuminated on n-ZnO:N/p-SiNW, I-V curve showed about three times larger photocurrent generation than film structure at 10 V reverse bias. Especially, at 660 nm wave length, the coaxial structure has 90.8% of external quantum efficiency (EQE) and 0.573 A/W of responsivity.

• Advances in nano research
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• v.2 no.2
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• pp.111-119
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• 2014

The chemical synthesis of anisotropic defective polyaniline/Ag composite (PANI/Ag) is explored using silver nitrate ($AgNO_3$) as the precursor material. This study provides a simple method for the formation of PANI/Ag nanocomposites at two different aniline concentrations $5{\mu}l$ (PANC5) and $10{\mu}l$ (PANC10). The composite PANC5 exhibits UV-Visible absorption peaks at 436 nm and 670 nm whereas, PANC10 exhibits absorption peaks at 446 nm and 697 nm. This shift is caused by the strong interaction between polyaniline and silver. The characterized FTIR peaks observed at around $3410cm^{-1}$ (PANC5) and $3420cm^{-1}$ (PANC10) was due to the N-H stretching vibrations. The appearance of a broad band instead of a sharp peak can be attributed due to the presence of a high concentration of N-H groups in the nanocomposite. The TEM images show that the sample contains defective spherical, truncated triangular and rod shaped particles. The results showed that the PANI/Ag nanocomposites are composed of nano-sized particles of 43-53 nm that contain Ag domains of 33-37 nm with polymer thickness 5.7-11.2 nm at two different aniline concentrations.