• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.7
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• pp.662-666
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• 2005

Silicon nitride $(SiN_x)$ film is a promising material for anti-reflection coating and passivation of multicrystalline silicon (me-Si) solar cells. In this work, a plasma-enhanced chemical vapor deposition (PECVD) system with batch-type reactor tube was used to prepare highly robust $SiN_x$ films for screen-printed mc-Si solar cells. The Gas flow ratio, $R=[SiH_4]/[NH_3]$, in a mixture of silane and ammonia was varied in the range of 0.0910.235 while maintaining the total flow rate of the process gases to 4,200 sccm. The refractive index of the $SiN_x$ film deposited with a gas flow ratio of 0.091 was measured to be 2.03 and increased to 2.37 as the gas flow ratio increased to 0.235. The highest efficiency of the cell was $14.99\%$ when the flow rate of $SiH_4$ was 350 sccm (R=0.091). Generally, we observed that the efficiency of the mc-Si solar cell decreased with increasing R. From the analysis of the reflectance and the quantum efficiency of the cell, the decrease in the efficiency was shown to originate mainly from an increase in the surface reflectance for a high flow rate of $SiH_4$ during the deposition of $SiN_x$ films.

• Proceedings of the KSRS Conference
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• 1998.09a
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• pp.376-381
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• 1998

In this study, we was measured the radiance reflectance by using multi-spectral image of low resolution camera(LRC) which will be loaded in the multi-purpose satellite(KOMPSAT) to use the data in analyzing water pollution. Also we investigated the possibility of extraction of water quality factors in rivers and water body by using high resolution remote sensing data such as Airborne MSS. Especially, we tried to extract the environmental factors related with eutrophication, and also tried to develop the process technique and the radiance feature of reflectance related with eutrophication. The results were summarized as follows: First, the spectrum of sun's rays which reaches the surface of the earth was consistent with visible rays bands of 0.4${\mu}{\textrm}{m}$~0.7${\mu}{\textrm}{m}$ and about 50% of total quantity of radiation were there. And at around 0.5${\mu}{\textrm}{m}$ of green spectral band in visible rays bands, the spectrum was highest. Second, as a result of the radiance reflectance Chlorophyll-a represented high spectral reflectance mainly around 0.52${\mu}{\textrm}{m}$ of green spectral band, and suspended sediments and turbidity represented high spectral reflectance at 0.8${\mu}{\textrm}{m}$ and at 0.57${\mu}{\textrm}{m}$ each. Third, as a result of the water quality analysis by using Airborne MSS, Chlorophyll-a could have a distribution chart when carried out ratio of B3 and BS to B7. And Band 7 was useful for making the distribution chart of suspended sediments. And when we carried out PCA, suspended sediments and turbidity had distributions at PC 1 , PC 4 each similarly to ground truth data. Above results can be changed according to the change of season and time. Therefore, in order to analyze more exactly the environmental factors of water quality by using LRC data, we need to investigate constantly the ground truth data and the radiance feature of reflectance of water body. Afterward in this study, we will constantly analyze the radiance feature of the surface of water in water body by measuring the on-the-spot radiance reflectance and using low resolution satellite image(SeaWiFs). Besides, we will gather the data of water quality analysis in water body and analyze the pattern of water pollution.

• Journal of Space Technology and Applications
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• v.3 no.2
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• pp.154-164
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• 2023

In space exploration, spectroscopic observation is useful for understanding objects' composition and physical properties. There are various methods for analyzing spectral data, and there are differences depending on the object and the wavelength. This paper introduces a method for analyzing visible & nearinfrared (VNIR) spectral data, which is mainly applied in lunar exploration. The main analysis methods include false color ratio image processing, reflectance pattern analysis, integrated band depth (IBD) processing, and continuum removal as preprocessing before analysis. These spectroscopic analysis methods help to understand the mineral properties of the lunar surface in the VNIR region and can be applied to other celestial bodies such as Mars.

• Korean Journal of Materials Research
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• v.23 no.2
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• pp.112-115
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• 2013

One of the most important characteristics of Mg alloys is the high ratio of strength to weight. This is why there is a high demand for applications with these alloys in the transportation industries to reduce the fuel consumption and to save energy. In addition, magnesium (and its alloys) is of considerable interest as a structural material, especially in the aerospace and automotive industries thanks to its low density. However, its major drawback is its high sensitivity to corrosion. Therefore, its use requires the application of a surface treatment. This study used a die-casted AZ91D Mg alloyand all the samples were annealed (in $120^{\circ}C$). The surface microstructure and phase distribution in thin-walled AZ91D magnesium components cast on a hot-chamber die-casting machine were investigated by optical microscopy and scanning electron microscopy. The reflectance differences in the bulk state comparison with the annealing state are caused by hydrogenation presence of the Mg layer under an oxidation surface layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.323-323
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• 2010

Saw damage of crystalline silicon wafer is unavoidable factor. Usually, alkali treatment for removing the damage has been carried out as the saw damage removal (SDR) process for priming the alkali texture. It usually takes lots of time and energy to remove the sawed damages for solar grade crystalline silicon wafers We implemented two different mixed acidic solution treatments to obtain the improved surface structure of silicon wafer without much sacrifice of the silicon wafer thickness. At the first step, the silicon wafer was dipped into the mixed acidic solution of $HF:HNO_3$=1:2 ration for polished surface and at the second step, it was dipped into the diluted mixed acidic solution of $HF:HNO_3:H_2O$=7:3:10 ratio for porous structure. This double treatment to the silicon wafer brought lower reflectance (25% to 6%) and longer carrier lifetime ($0.15\;{\mu}s$ to $0.39\;{\mu}s$) comparing to the bare poly-crystalline silicon wafer. With optimizing the concentration ratio and the dilution ratio, we can not only effectively substitute the time consuming process of SDR to some extent but also skip plasma enhanced chemical vapor deposition (PECVD) process. Moreover, to conduct alkali texture for pyramidal structure on silicon wafer surface, we can use only nitric acid rich solution of the mixed acidic solution treatment instead of implementing SDR.

• Korean Journal of Remote Sensing
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• v.40 no.4
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• pp.319-341
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• 2024

The utilization of multispectral imaging systems (MIS) in remote sensing has become crucial for large-scale agricultural operations, particularly for diagnosing plant health, monitoring crop growth, and estimating plant phenotypic traits through vegetation indices (VIs). However, environmental factors can significantly affect the accuracy of multispectral reflectance data, leading to potential errors in VIs and crop status assessments. This paper reviewed the complex interactions between environmental conditions and multispectral sensors emphasizing the importance of accounting for these factors to enhance the reliability of reflectance data in agricultural applications.An overview of the fundamentals of multispectral sensors and the operational principles behind vegetation index (VI) computation was reviewed. The review highlights the impact of environmental conditions, particularly solar zenith angle (SZA), on reflectance data quality. Higher SZA values increase cloud optical thickness and droplet concentration by 40-70%, affecting reflectance in the red (-0.01 to 0.02) and near-infrared (NIR) bands (-0.03 to 0.06), crucial for VI accuracy. An SZA of 45° is optimal for data collection, while atmospheric conditions, such as water vapor and aerosols, greatly influence reflectance data, affecting forest biomass estimates and agricultural assessments. During the COVID-19 lockdown,reduced atmospheric interference improved the accuracy of satellite image reflectance consistency. The NIR/Red edge ratio and water index emerged as the most stable indices, providing consistent measurements across different lighting conditions. Additionally, a simulated environment demonstrated that MIS surface reflectance can vary 10-20% with changes in aerosol optical thickness, 15-30% with water vapor levels, and up to 25% in NIR reflectance due to high wind speeds. Seasonal factors like temperature and humidity can cause up to a 15% change, highlighting the complexity of environmental impacts on remote sensing data. This review indicated the importance of precisely managing environmental factors to maintain the integrity of VIs calculations. Explaining the relationship between environmental variables and multispectral sensors offers valuable insights for optimizing the accuracy and reliability of remote sensing data in various agricultural applications.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.2
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• pp.109-113
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• 2013

ZnO thin films were synthesized on Si substrates by MOCVD using diethyl zinc as a precursor. Effects of $O_2$/DEZ gas mixing ratio on the growth rate, surface morphology, preferred orientation, and electrical properties of the ZnO thin films were investigated with SEM, XRD, and Hall measurement. The surface reflectance variations of ZnO thin films were analyzed using laser-photometer apparatus. As the $O_2$/DEZ mixing ratio increased, growth rate and $I_{(002)}/I_{(101)}$ in XRD of ZnO thin films decreased, and the crystal structure was changed from columnar to planar structure. All ZnO films deposited at various CVD conditions exhibited c-axis (002) plane preferred orientation. The electrical properties of ZnO thin films mainly depended on the carrier mobility.

• Journal of the Korean institute of surface engineering
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• v.31 no.6
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• pp.389-392
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• 1998

We have investigated the crystal properties of the Cd0.96Zn0.04Te(CZT) films evaporated on the Si(100) substrates by Elecctron Beam Evaporator(EBE) techique. The compositions of the As-preared films were different about 4% of atomic ratio, The films stucture was observad to be polycrystalline in cubic phase. Diffraction peaks were notable at the substrate temperature of $300^{\circ}C$. The reflectance measurements yield $E_1$=3.25~3.29 eV $E_1$+${\Delta}_1$=3.76~3.83 eV and $E_2$=5.08 eV,showing that the films wear in cubic phase. For the film evaporated at the substrate temperature of $150^{\circ}C$, the peaks of photocurrent are at 720nm and 980nm.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.8
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• pp.3800-3805
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• 2012

Infrared(IR) reflective black cool pigment and paint which is used for interior/exterior materials(IR reflectance >30%) to prevent heat island effect and to increase energy efficiency were studied. Cool pigment was synthesized using mixture of $Fe_2O_3$ and $Cr_2O_3$ with calcination from 900 to $1,200^{\circ}C$. Cool paint was prepared by formulation of cool pigment, acrylic resins, and other additives. Results showed that optimum color fixation of pigment obtained by mole ratio of Fe to Cr was 0.9 with calcination temperature at $1,000^{\circ}C$. The cool paint formulated by 20% pigment and 1.5% dispersive additive with $125{\mu}m$ thickness of coated layer showed optimum IR reflectance. Temperature difference on surface between cool paint and ordinary paint(STD) was $36.5^{\circ}C$ and IR reflectance(TSR) was 39.3% at wavelength from 700 to 2,500nm. And color change was not detected during 500hrs weathering test.

• Journal of the Korean institute of surface engineering
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• v.49 no.2
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• pp.135-140
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• 2016

In this study, we prepared magnesium ion containing oxide films formed on the Ti-6Al-4V using plasma electrolytic oxidation (PEO) treatment. Ti-6Al-4V surface was treated using PEO in Mg containing electrolytes at 270V for 5 min. The phase, composition and morphology of the Mg ion containing oxide films were evaluated with X-ray diffraction (XRD), Attenuated total reflectance Fourier transform infrared (ATR-FTIR) and filed-emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray spectrometer (EDS). The biocompatibility of Mg ion containing oxide films was evaluated by immersing in simulated body fluid (SBF). According to surface properties of PEO films, the optimum condition was formed when the applied was 270 V. The PEO films formed in the condition contained the properties of porosity, anatase phase, and near 1.7 Ca(Mg)/P ratio in the oxide film. Our experimental results demonstrate that Mg ion containing oxide promotes bone like apatite nucleation and growth from SBF. The phase and morphologies of bone like apatite were influenced by the Mg ion concentration.