• Journal of Magnetics
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• v.4 no.4
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• pp.119-122
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• 1999

Magnetic properties and crystal structures of (Fe1-XCoX) Pt (X = 0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1.0) ternary thin films were investigated. The order-disorder phase transformation of FePt thin films during annealing was also studied by x-ray diffraction and M ssbauer spectroscopy. The magnetic thin films were deposited on glass substrates using a dc sputtering method and were subsequently annealed at 400~$700^{\circ}C$ in a high vacuum. The as-deposited films exhibited a high degree of the <111> preferred orientation and the preferred orientation was not destroyed even after the subsequent post annealing. The coercivity of the ($Fe_xCo_{1-x}$) Pt thin films annealed at $700^{\circ}C$ showed a minimum value at the equiatomic composition of the Fe and Co atoms. The ordered structure of the FePt alloy was thought to have formed from the disordered structure by an inhomogeneous process, which was confirmed by the asymmetric peak shapes and M ssbauer spectra.

• Journal of the Korea Furniture Society
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• v.14 no.2
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• pp.21-29
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• 2003

This study was carried out to investigate characteristics of plywood overlaid with softwood veneers densified by resin impregnation and compression. The resin impregnability of Korean pine veneer under atmospheric pressure soaking was greater than that of larch, and impregnability of melamine resin was slightly greater than phenolic resin. It was suggested that resin impregnation ratio was affected by density and thickness of veneer. The largest melamine resin impregnation ratio of 50.7% was obtained with 1.26mm thick Korean pine veneer, and the lowest phenolic resin impregnation ratio of 11.7% with 3.41mm thick larch veneer. Therefore, it was suggested that the vacuum-pres sure-soak treatment is required at thick larch veneer. In densifying resin-impregnated veneers, densification ratio from 13.4 to 31.2% was obtained by high pressure from 15.6 to $20.8kgf/cm^2$. Impregnation of melamine resin also showed relatively greater at densification than that of phenolic resin. So it showed the degree of densification of about 20% or greater. It was seemed that adhesive bonding strength of plywood(base panel) which was directly pressed and overlaid with resin-impregnated veneer was affected by resin tackiness after resin impregnation followed by semi-drying. In laboratory scale, melamine resin impregnation was more favorable for the development of adhesive bonding strength owing to moisture control.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.321-324
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• 2005

The main purpose of the present study has been placed on investigating the effects of controlled rolling and cooling on the microstructures and mechanical properties of C-Si-Mn-V steels for cold forming. The steels were manufactured in vacuum induction melting(VIM) furnace and casted to 1.1ton Ingots and the ingots were forged to $\Box150$ billet. The forged billets were reheated in walking beam furnace and rolled to coil, the stocks were rolled by Controlled Rolling and Cooling Technology (CRCT), so rolled at low temperature by water spraying applied in rolling stage and acceleratly cooled before coiling. Rolled coils were cold drawed to the degree of $27\%$ of area reduction without heat treatment. Microstructual observation, tensile test, compression test and charpy impact tests were conducted. The mechanical properties of the steels were changed by area reduction of cold drawing and it is founded that there are optimum level of cold drawing to minimize compression stress for these steels. From the result of this study, it is conformed that mechanical properties and microstructure of C-Si-Mn-V steels for cold forming were enhanced by accelerated cooling and founded optimum level of cold drawing.

• The Journal of Engineering Geology
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• v.33 no.1
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• pp.85-103
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• 2023

The in-situ remediation of a solidified stratum containing a large amount of fine-texture material like clay or organic matter in contaminated soil faces limitations such as increased remediation cost resulting from decreased purification efficiency. Even if the soil conditions are good, remediation generally requires a long time to complete because of non-uniform soil properties and low permeability. This study assessed the remediation effect and evaluated the field applicability of a methodology that combines pneumatic fracturing, vacuum extraction, and plasma blasting (the PPV method) to improve the limitations facing existing underground remediation methods. For comparison, underground remediation was performed over 80 days using the experimental PPV method and chemical oxidation (the control method). The control group showed no decrease in the degree of contamination due to the poor delivery of the soil remediation agent, whereas the PPV method clearly reduced the degree of contamination during the remediation period. Remediation effect, as assessed by the reduction of the highest TPH (Total Petroleum Hydrocarbons) concentration by distance from the injection well, was uncleared in the control group, whereas the PPV method showed a remediation effect of 62.6% within a 1 m radius of the injection well radius, 90.1% within 1.1~2.0 m, and 92.1% within 2.1~3.0 m. When evaluating the remediation efficiency by considering the average rate of TPH concentration reduction by distance from the injection well, the control group was not clear; in contrast, the PPV method showed 53.6% remediation effect within 1 m of the injection well, 82.4% within 1.1~2.0 m, and 68.7% within 2.1~3.0 m. Both ways of considering purification efficiency (based on changes in TPH maximum and average contamination concentration) found the PPV method to increase the remediation effect by 149.0~184.8% compared with the control group; its average increase in remediation effect was ~167%. The time taken to reduce contamination by 80% of the initial concentration was evaluated by deriving a correlation equation through analysis of the TPH concentration: the PPV method could reduce the purification time by 184.4% compared with chemical oxidation. However, the present evaluation of a single site cannot be equally applied to all strata, so additional research is necessary to explore more clearly the proposed method's effect.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.129-129
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• 2016

Graphene, as a single layer of $sp^2$-bonded carbon atoms packed into a 2D honeycomb crystal lattice, has attracted much attention due to its outstanding properties. In order to synthesize high quality graphene, transition metals, such as nickel and copper, have been widely employed as catalysts, which needs transfer to desired substrates for various applications. However, the transfer steps are not only complicated but also inevitably induce defects, impurities, wrinkles, and cracks of graphene. Furthermore, the direct synthesis of graphene on dielectric surfaces has still been a premature field for practical applications. Therefore, cost effective and concise methods for transfer-free graphene are essentially required for commercialization. Here, we report a facile transfer-free graphene synthesis method through nickel and carbon co-deposited layer. In order to fabricate 100 nm thick NiC layer on the top of $SiO_2/Si$ substrates, DC reactive magnetron sputtering was performed at a gas pressure of 2 mTorr with various Ar : $CH_4$ gas flow ratio and the 200 W DC input power was applied to a Ni target at room temperature. Then, the sample was annealed under 200 sccm Ar flow and pressure of 1 Torr at $1000^{\circ}C$ for 4 min employing a rapid thermal annealing (RTA) equipment. During the RTA process, the carbon atoms diffused through the NiC layer and deposited on both sides of the NiC layer to form graphene upon cooling. The remained NiC layer was removed by using a 0.5 M $FeCl_3$ aqueous solution, and graphene was then directly obtained on $SiO_2/Si$ without any transfer process. In order to confirm the quality of resulted graphene layer, Raman spectroscopy was implemented. Raman mapping revealed that the resulted graphene was at high quality with low degree of $sp^3$-type structural defects. Additionally, sheet resistance and transmittance of the produced graphene were analyzed by a four-point probe method and UV-vis spectroscopy, respectively. This facile non-transfer process would consequently facilitate the future graphene research and industrial applications.

• Journal of the Korean Vacuum Society
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• v.18 no.3
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• pp.213-220
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• 2009

The optimal condition of low temperature deposition of transparent conductive Al-doped zinc oxide (AZO) films is studied by RF magnetron sputtering method. To achieve enhanced-electrical property and good crystallites quality, we tried to deposit on glass using a two-step growth process. This process was to deposit AZO buffer layer with optimal growth condition on glass in-situ state. The AZO film grown at rf 120 W on buffer layer prepared at RF $50{\sim}60\;W$ shows the electrical resistivity $3.9{\times}10^{-4}{\Omega}cm$, Carrier concentration $1.22{\times}10^{21}/cm^3$, and mobility $9.9\;cm^2/Vs$ in these results, The crystallinity of AZO film on buffer layer was similar to that of AZO film on glass with no buffer later but the electrical properties of the AZO film were 30% improved than that of the AZO film with no buffer layer. Therefore, the cause of enhanced electrical properties was explained to be dependent on degree of crystallization and on buffer layer's compressive stress by variation of $Ar^+$ ion impinging energy.

• Journal of the Korean Vacuum Society
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• v.6 no.4
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• pp.364-371
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• 1997

Silicon trench etching has been carried out using a magnetically enhanced reactive ion etching system in HBr plasma containing He-$O_2$, $CF_4$. The changes of etch rate and etch profile, the degree of residue formation, and the change of surface chemical state were investigated as a function of additive gas flow rate. A severe lateral etching was observed when pure HBr plasma was used to etch the silicon, resulted in a pot shaped trench. When He-$O_2$, $SiF_4$ additives were added to HBr plasma, the lateral etching was almost eliminated and a better trench etch profile was obtained. The surface etched in HBr/He-$O_2/SiF_4$ plasma showed relatively low contamination and residue elements compared to the surface etched in HBr/He-$O-2/CF_4$plasma. In addition, the etching characteristics including low residue formation and chemically clean etched surface were obtained by using HBr containing He-$O_2$ or $SiF_4$ additive gases instead of $CF_4$ gas, which were confirmed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM).

• Journal of the Korean Vacuum Society
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• v.21 no.1
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• pp.62-68
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• 2012

The conversion efficiency of solar cells depending on incident angle of light is important for building-integrated photovoltaics (BIPV) applications. The quantum efficiency is the ratio of the number of charge carriers collected by the solar cell to the number of photons of a given energy shining on the solar cell. The analysis of angle dependence of quantum efficiencies give more information upon the variation of power output of a solar cell by the incident angle of light. The variations in power output of solar cells with increasing angle of incidence is different for the type of cell structures. In this study we present the results of the quantum efficiency measurement of single-crystalline silicon solar cells and a-Si:H thin-film solar cells with the angle of incidence of light. As a result, as the angle of incidence increases in single-crystalline silicon solar cells, quantum efficiency at all wavelength (300~1,100 nm) of light were reduced. But in case of a-Si:H thin-film solar cells, quantum efficiency was increased or maintained at the angle of incidence from 0 degree to about 40 degrees and dramatically decrease at more than 40 degrees in the range of visible light. This results of quantum efficiency with increasing incident angle were caused by haze and interference effects in thin-film structure. Thus, the structural optimization considering incident angle dependence of solar cells is expected to benefit BIPV.

• Journal of the Korean Vacuum Society
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• v.7 no.1
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• pp.17-23
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• 1998

$Pb(Fe_{0.5}Nb_{0.5}O_3(PFN)$ thin films were prepared by rf magnetron co-sputtering method on $SiO_2/Si$, ITO/glass, and $Pt/Ti/SiO_2/Si$ substrates and post-annealed at the $N_2$ atmosphere by RTA(rapid thermal annerling). The degree of crystallinity of PFN films was identified on various substrates. Electrical properties of PFN films was characterized for $Pt/PFN/Pt/Ti/SiO_2/Si$ structure. The composition of PFN films was estimated by EPMA (electron probe micro analysis). PFN films would be crystallized better to perovskite phase on ITO/glass substrate than $SiO_2/Si$ substrate. This may be induced by the deformation of Pb deficient pyrochlore phase due to Pb diffusion into $SiO_2/Si$ substrate. PFN films on $Pt/Ti/SiO_2/Si$ substrate. PFN films with 5-10% Pb excess were crystallized to perovskite phase from $500^{\circ}C$ temperature. In summary, we show that Pb composition and annealing temperature were critically influenced on crystallinity to perovskite phase. When PFN film with 17% Pb excess was annealed at $600^{\circ}C$ at the $N_2$ atmosphere for 300kV/cm and 88. Its remnant polarization coercive field $2.0 MC/cm^2$ and 144kV/cm, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.239-240
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• 2012

With advancements in semiconductor device technologies, manufacturing processes are getting more complex and it became more difficult to maintain tighter process control. As the number of processing step increased for fabricating complex chip structure, potential fault inducing factors are prevail and their allowable margins are continuously reduced. Therefore, one of the key to success in semiconductor manufacturing is highly accurate and fast fault detection and classification at each stage to reduce any undesired variation and identify the cause of the fault. Sensors in the equipment are used to monitor the state of the process. The idea is that whenever there is a fault in the process, it appears as some variation in the output from any of the sensors monitoring the process. These sensors may refer to information about pressure, RF power or gas flow and etc. in the equipment. By relating the data from these sensors to the process condition, any abnormality in the process can be identified, but it still holds some degree of certainty. Our hypothesis in this research is to capture the features of equipment condition data from healthy process library. We can use the health data as a reference for upcoming processes and this is made possible by mathematically modeling of the acquired data. In this work we demonstrate the use of recurrent neural network (RNN) has been used. RNN is a dynamic neural network that makes the output as a function of previous inputs. In our case we have etch equipment tool set data, consisting of 22 parameters and 9 runs. This data was first synchronized using the Dynamic Time Warping (DTW) algorithm. The synchronized data from the sensors in the form of time series is then provided to RNN which trains and restructures itself according to the input and then predicts a value, one step ahead in time, which depends on the past values of data. Eight runs of process data were used to train the network, while in order to check the performance of the network, one run was used as a test input. Next, a mean squared error based probability generating function was used to assign probability of fault in each parameter by comparing the predicted and actual values of the data. In the future we will make use of the Bayesian Networks to classify the detected faults. Bayesian Networks use directed acyclic graphs that relate different parameters through their conditional dependencies in order to find inference among them. The relationships between parameters from the data will be used to generate the structure of Bayesian Network and then posterior probability of different faults will be calculated using inference algorithms.