• Applied Science and Convergence Technology
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• v.26 no.1
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• pp.11-15
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• 2017

To improve the adhesion of Mo thin film as a back contact material, a DC magnetron sputtering system was used to deposit in the form of a bi-layer on soda-lime glass. Films with low resistivity and good adhesion were obtained from this deposition, even though the two qualities were found be hard to obtain at the same time. The best Mo bi-layer showed a resistivity of $8.13{\times}10^{-4}{\Omega}{\cdot}cm$ at $500^{\circ}C$ and $3.0{\times}10^{-3}\;Torr$. The XRD measurements showed that the crystallites of the films were mainly oriented in the (110) direction, the FE-SEM images revealed that the resistivity of the Mo films decreased with increasing substrate temperature, which temperature reduction is accompanied by an increase of the grain size. These experimental results were analyzed using the Fuchs-Sondheimer theory. Our Mo bi-layer film with better crystallinity and lower resistivity can be suitably used as a back-contact layer for CIGS solar cells.

• Proceedings of the Membrane Society of Korea Conference
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• 2002.04a
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• pp.23-46
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• 2002

The cryogenic, pressure swing adsorption and membrane methods have been used to separate air into nitrogen and oxygen. The air separation membrane is made of the polymers, of which manufacturing process is complicate and it causes a little high production cost. Polymer membrane has temperature limit in usage and low durability even at moderate temperature. Therefore, inorganic membranes have been studied for years. As formation of unit alumino-silicate membrane, unit cells of membrane were made with a few coating methods. In this study the dipping of substrate into sols, application of vacuum to the opposite side of substrate with coating and rotating of the substrate in the sols were found as good coating memthods to make a uniform coating and to control the thickness of membrane. The membrane coats were examined by SEM and XRD. The sample ESZl-1 was compared with those of samples that prepared by another method. The present developed coating methods could be applied to the various types of zeolite membrane formation, that is A- X-, Y- ZSM- and MCM-types of membranes. Also these membrane forming methods could be applied to formation of catalyst absorbed zeolite membrane, of which zeolite absorb the catalytic metals. The product obtained from these coating methods could be applied to the industrial gas and liquid phase catalytic reaction and separation processes.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.98.2-98.2
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• 2012

Thin film solar cells are growing up in the market due to their high efficiency and low cost. Especially CdTe and $CuInGaSe_2$ based solar cells are leading the other cells, but due to the limited percentage of the elements present in our earth's crust like Tellurium, Indium and Gallium, the price of the solar cells will increase rapidly. Copper Zinc Tin Sulfide (CZTS) and Copper Zinc Tin Selenide (CZTSe) semiconductor (having a kesterite crystal structure) are getting attention for its solar cell application as the absorber layer. CZTS and CZTSe have almost the same crystal structure with more environmentally friendly elements. Various authors have reported growth and characterization of CZTSe films and solar cells with efficiencies about 3.2% to 8.9%. In this study, a novel method to prepare CZTSe has been proposed based on selenization of stacked Copper Selenide ($Cu_2Se$), Tin Selenide ($SnSe_2$) and Zinc Selenide (Zinc Selenide) in six possible stacking combinations. Depositions were carried out through RF magnetron sputtering. Selenization of all the samples was performed in Close Space Sublimation (CSS) in vacuum at different temperatures for three minutes. Characterization of each sample has been performed in Field Emission SEM, XRD, Raman spectroscopy, EDS and Auger. In this study, the properties and results of $Cu_2ZnSnSe_4$ thin films grown by selenization will be presented.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.460-463
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• 2000

The current-voltage characteristics of the sandwich system at different annealing temperatures and different bias voltages have been studied. In order to prepare the Al/V$O_X$/Al sandwich devices structure, thin films of vanadium oxide(V$O_X$) was deposited by r.f. magnetron sputtering from $V_2$$O_5$ target in 10% gas mixture of argon and oxygen, and annealed during lhour at different temperatures in vacuum. Crystall structure, surface morphology, and thickness of films were characterized through XRD, SEM and I-V characteristics were measured by electrometer. The films prepared below 20$0^{\circ}C$ were amorphous, and those prepared above 300 $^{\circ}C$were polycrystalline. At low fields electron injected to conduction band of vanadium oxide and formed space charge, current was limited by trap. Conduction mechanism at mid fields due to Schottky emission, while at high fields it changed to Fowler-Nordheim tunneling effects.

• Journal of the Korean institute of surface engineering
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• v.33 no.5
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• pp.319-328
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• 2000

Silver is known to have such characteristics as low shear strength, good transfer-film forming tendency, and good corrosion resistance. Silver thin films have been prepared by ion plating of physical vapour deposition (PVD) using both argon gas pressure and bias voltage of processing condition. After the silver films were prepared, the properties in them were examined by gas pressure and bias voltage of substrate. Their morphology and crystal orientation were investigated by scanning electron microscopy (SEM) and X-ray diffractor. The properties of film were, also, studied to relate with morphology, X-ray diffraction pattern, and friction coefficient at vacuum ambient. The friction coefficient was stabilized remarkably on deposited films with increasing argon pressure for deposition. Also, the effect of increasing of the bias voltage for deposition resulted in lower friction coefficient and stability in $1.7$\times$10^{-4}$ torr. On the contrary, behavior of friction coefficient was stabilized on deposited films with decreasing the bias voltage in $1.7$\times$10^{-5}$ torr for deposition.

• Journal of the Korean Vacuum Society
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• v.22 no.3
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• pp.156-161
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• 2013

We fabricated transparent conductive electrodes with silver (Ag) nanofibers by electrospinning process. Ag nanofibers have high aspect ratio and fused junctions which result in low sheet resistance. Electrospinning is a fast and efficient process to fabricate continuous one-dimensional (1D) nanofibers. Ag/polymer ink were prepared in polymer matrix solution by a sol-gel method. Then, Ag/polymer nanofibers precursors are heated at $200{\sim}500^{\circ}C$ in air for 2 h to eliminate partially the polymers. The topographical features of the Ag nanofibers were characterized by FE-SEM, and the electrical property was analyzed through I-V measurement system. Finally, optical property was measured using UV/VIS spectroscopy. The transparent conductive electrodes with Ag nanofibers exhibited a sheet resistance (Rs) of $250{\Omega}/sq$ at a transparency (T) of 83%. Transparent conductive films, contain the Ag nanofibers as conductive materials, have good electrical, optical, and mechanical properties. Therefore, it is expected to be useful for the application of flexible display in the future.

• Journal of the Korean Vacuum Society
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• v.15 no.6
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• pp.612-618
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• 2006

Surface modification of PTFE by ion irradiation was performed to improve its surface properties, In the case where argon was used to irradiate the PTFE films, an increase in the adhesion strength was observed when the ion fluence was over $1\times10^{15}\;ions/cm^2$, but the surface morphology dramatically changed to a needle-shaped one. However, when we used hydrogen ions under $O_2$ environmental gas, the adhesion strength increased at an ion fluence of $5\times10^{16}\;ions/cm^2$ and the surface morphology by the hydrogen irradiation was not needle-shaped. The surface morphology and adhesion strength of the hydrogen modified PTFE was influenced by the oxygen flow rate. It was confirmed by reflectance measurements that the surface properties of the hydrogen ion irradiated PTFE were superior to those of the argon ion irradiated PTFE.

• Research in Plant Disease
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• v.27 no.1
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• pp.8-16
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• 2021

This study was conducted to check the sterilization efficacy of microwave plasma (MWP) against the watermelon seeds infected with Acidovorax citrulli 11-251. Watermelon seeds were artificially vacuum inoculated to produce A. citrulli 11-251 infected seeds. Aac ImmunoStrip and scanning electron microscope (SEM) results suggests that, seeds (coat and endosperm) were infected under the concentration of 1×107/30 min. MWP sterlization process was carried out at 50 W (3 min, 5 min, and 10 min), 80 W (3 min, 5 min, and 10 min), and 100 W (3 min, 5 min, and 10 min). According to the results, MWP sterilized the artificially inoculated seed coats by 95.96% at 80 W/10 min and seed endosperms by 100% at 100 W/10 min respectively. Although, seeds were sterlized by MWP, germination rate of seeds were low as compared to non treated (negative control) seeds. Moreover, cell membrane of A. citrulli 11-251 was damaged while observed in SEM after sterilized with MWP. Further studies regarding the appropriate sterilization condition by MWP against A. citrulli infected seeds for germination will be conducted in our next study.

• Food Science and Preservation
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• v.31 no.3
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• pp.423-432
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• 2024

In this study, a vacuum tumbler with 4 impellers (DVT) was designed and applied for thawing frozen pork (vacuum -60 kPa, jacket 35℃, 1 rpm). Quality characteristics of the thawed pork were compared with those of industrially thawed meat by natural air at room temperature (NAT) and imported vacuum tumbler (IVT). The thawing time for frozen pork (303.36 kg) using DVT (165 min) was much shorter than that of NAT (4,200 min). DVT-thawed pork had lower drip loss (0.85%) than NAT (2.08%). DVT-thawed pork showed a pH of 5.92, a total bacterial count of 1.96±0.02 log CFU/g and no coliforms. Deteriorations in fat (TBARS 0.31±0.01 MDA mg/kg) and protein (VBN 5.67±1.98 mg%) in DVT-thawed pork were significantly lower than those of NAT (p<0.05). DVT-thawed pork had a high water-holding capacity (WHC, 97.5%). The hardness (34.59±0.46 N) and chewiness (188.21±0.17) of cooked DVT-thawed pork were about 5-6 times lower than those of NTA. Microstructure (SEM) showed myofibrillar damage in NAT-thawed pork, whereas dense myofibrillar structure was observed in DVT-thawed pork. DVT was better or similar to IVT in all evaluation parameters. The designed DVT is expected to be used as an efficient thawing method in terms of processing time and yield and to produce thawed meat with high WHC, soft texture, and low spoilage by minimizing tissue damage.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.57.2-57.2
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• 2011

Dye-sensitized solar cells (DSSC) have recently been developed as a cost-effective photovoltaic system due to their low-cost materials and facile processing. The production of DSSC involves chemical and thermal processes but no vacuum is involved. Therefore, DSSC can be fabricated without using expensive equipment. The use of dyes and nanocrystalline $TiO_2$ is one of the most promising approaches to realize both high performance and low cost. The efficiency of the DSSC changes consequently in the particle size, morphology, crystallization and surface state of the $TiO_2$. Nanocrystalline $TiO_2$ materials have been widely used as a photo catalyst and an electron collector in DSSC. Front electrode in DSSC are required to have an extremely high porosity and surface area such that the dyes can be sufficiently adsorbed and be electronically interconnected, resulting in the efficient generation of photocurrent within cells. In this study, DSSC were fabricated by an screen printing for the $TiO_2$ thin film. $TiO_2$ nanoparticles characterized by X-ray diffractometer (XRD) and scanning electron microscope (SEM) and scanning auger microscopy (SAM) and zeta potential and electrochemical impedance spectroscopy(EIS).In addition, DSSC module was modeled and simulated using the SILVACO TCAD software program. Improve the efficiency of DSSC, the effect of $TiO_2$ thin film thickness and $TiO_2$ nanoparticle size was investigated by SILVACO TCAD software program.