• Journal of Radiation Industry
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• v.4 no.3
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• pp.265-269
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• 2010

Silicon-based non-oxide ceramic carbide fiber is one of the leading candidate ceramic materials for engineering applications because of its excellent mechanical properties at high temperature and good chemical resistance. In this study, polycarbosilane(PCS) and zirconium butoxide were used as a precursor to prepare polyzirconocarbosilane (PZC) fibers. A polymer solution was prepared by dissolving PCS in zirconium butoxide (50/50 wt%). This solution was heated at $250^{\circ}C$ in a nitrogen atmosphere for 2 hour with stirring, and then dried in a vacuum oven for 48 hour. PZC fibers were fabricated using an electrospinning technique. The fibers were irradiated with an electron beam to induce structural crosslinking. Crosslinked PZC fibers were heat treated at $1,300^{\circ}C$ in a nitrogen atmosphere. The microstructures of PZC fibers were examined by SEM. Chemical structures of PZC fibers were examined by FT-IR and XRD. Thermal stability of PZC fibers was investigated by TGA.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.173-179
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• 2018

Electrochemical characterization was conducted on poly(vinyl alcohol) (PVA)-ceramic composite (PVA-CC) separators for supercapacitor applications. The PVA-CC separators were fabricated by mixing various ceramic particles including aluminum oxide ($Al_2O_3$), silicon dioxide ($SiO_2$), and titanium dioxide ($TiO_2$) into a PVA aqueous solution. These ceramic particles help to create amorphous regions in the crystalline structure of the polymer matrix to increase the ionic conductivity of PVA. Supercapacitors were assembled using PVA-CC separators with symmetric activated carbon electrodes and electrochemical characterization showed enhanced specific capacitance, rate capability, cycle life, and ionic conductivity. Supercapacitors using the $PVA-TiO_2$ composite separator showed particularly good electrochemical performance with a 14.4% specific capacitance increase over supercapacitors using the bare PVA separator after 1000 cycles. With regards to safety, PVA becomes plasticized when immersed in 6 M KOH aqueous solution, thus there was no appreciable loss in tear resistance when the ceramic particles were added to PVA. Thus, the enhanced electrochemical properties can be attained without reduction in safety making the addition of ceramic nanoparticles to PVA separators a cost-effective strategy for increasing the ionic conductivity of separator materials for supercapacitor applications.

• Advances in Energy Research
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• v.3 no.2
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• pp.117-124
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• 2015

In this paper, we have reported an enhancement in thermoelectric properties of un-doped zinc oxide (ZnO) grown by molecular beam epitaxy (MBE) on silicon (001) substrate by annealing treatment. The grown ZnO thin films were annealed in oxygen environment at $500^{\circ}C-800^{\circ}C$, keeping a step of $100^{\circ}C$ for one hour. Room temperature Seekbeck measurements showed that Seebeck coefficient and power factor increased from 222 to $510{\mu}V/K$ and $8.8{\times}10^{-6}$ to $2.6{\times}10^{-4}Wm^{-1}K^{-2}$ as annealing temperature increased from 500 to $800^{\circ}C$ respectively. This observation was related with the improvement of crystal structure of grown films with annealing temperature. X-ray diffraction (XRD) results demonstrated that full width half maximum (FWHM) of ZnO (002) plane decreased and crystalline size increased as the annealing temperature increased. Photoluminescence study revealed that the intensity of band edge emission increased and defect emission decreased as annealing temperature increased because the density of oxygen vacancy related donor defects decreased with annealing temperature. This argument was further justified by the Hall measurements which showed a decreasing trend of carrier concentration with annealing temperature.

• Journal of the Optical Society of Korea
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• v.19 no.3
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• pp.217-221
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• 2015

Developing a metallization that has low cost and high efficiency is essential in solar-cell industries, to replace expensive silver-based metallization. Ni/Cu two-step metallization is one way to reduce the cost of solar cells, because the price of copper is about 100 times less than that of silver. Alkaline electroless plating was used for depositing nickel seed layers on the front electrode area. Prior to the nickel deposition process, 2% HF solution was used to remove native oxide, which disturbs uniform nickel plating. In the subsequent step, a nickel sintering process was carried out in $N_2$ gas atmosphere; however, copper was plated by light-induced plating (LIP). Plated nickel has different properties under different bath conditions because nickel electroless plating is a completely chemical process. In this paper, plating bath conditions such as pH and temperature were varied, and the metal layer's structure was analyzed to investigate the adhesion of Ni/Cu metallization. Average adhesion values in the range of 0.2-0.49 N/mm were achieved for samples with no nickel sintering process.

• Safety and Health at Work
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• v.12 no.3
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• pp.403-415
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• 2021

Background: This study aimed to assess the possibility of benzene exposure in workers of a Korean semiconductor manufacturing company by reviewing the issued patents. Methods: A systematic patent search was conducted with the Google "Advanced Patent Search" engine using the keywords "semiconductor" and "benzene" combined with all of the words accessed on January 24, 2016. Results: As a result of the search, we reviewed 75 patent documents filed by a Korean semiconductor manufacturing company from 1994 to 2010. From 22 patents, we found that benzene could have been used as one of the carbon sources in chemical vapor deposition for capacitor; as diamond-like carbon for solar cell, graphene formation, or etching for transition metal thin film; and as a solvent for dielectric film, silicon oxide layer, nanomaterials, photoresist, rise for immersion lithography, electrophotography, and quantum dot ink. Conclusion: Considering the date of patent filing, it is possible that workers in the chemical vapor deposition, immersion lithography, and graphene formation processes could be exposed to benzene from 1996 to 2010.

• Korean Journal of Materials Research
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• v.28 no.12
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• pp.758-762
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• 2018

The transfer characteristics of zinc tin oxide(ZTO) on silicon dioxide($SiO_2$) thin film transistor generally depend on the electrical properties of gate insulators. $SiO_2$ thin films are prepared with argon gas flow rates of 25 sccm and 30 sccm. The rate of ionization of $SiO_2$(25 sccm) decreases more than that of $SiO_2$(30 sccm), and then the generation of electrons decreases and the conductivity of $SiO_2$(25 sccm) is low. Relatively, the conductivity of $SiO_2$(30 sccm) increases because of the high rate of ionization of argon gases. Therefore, the insulating performance of $SiO_2$(25 sccm) is superior to that of $SiO_2$(30 sccm) because of the high potential barrier of $SiO_2$(25 sccm). The $ZTO/SiO_2$ transistors are prepared to research the $CO_2$ gas sensitivity. The stability of the transistor of $ZTO/SiO_2$(25 sccm) as a high insulator is superior owing to the high potential barrier. It is confirmed that the electrical properties of the insulator in transistor devices is an important factor to detect gases.

• Advances in nano research
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• v.10 no.1
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• pp.91-99
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• 2021

Silicene is an emerging two-dimensional (2D) semiconductor material which has been envisaged to be compatible with conventional silicon technology. This paper presents a theoretical study of uniformly doped silicene with aluminium (AlSi3) Field-Effect Transistor (FET) along with the benchmark of device performance metrics with other 2D materials. The simulations are carried out by employing nearest neighbour tight-binding approach and top-of-the-barrier ballistic nanotransistor model. Further investigations on the effects of the operating temperature and oxide thickness to the device performance metrics of AlSi3 FET are also discussed. The simulation results demonstrate that the proposed AlSi3 FET can achieve on-to-off current ratio up to the order of seven and subthreshold swing of 67.6 mV/dec within the ballistic performance limit at room temperature. The simulation results of AlSi3 FET are benchmarked with FETs based on other competitive 2D materials such as silicene, graphene, phosphorene and molybdenum disulphide.

• Journal of the Korean Society of Visualization
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• v.21 no.1
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• pp.67-73
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• 2023

In the study, pool boing critical heat flux (CHF) was experimentally investigated depending on the length of heaters. A smooth silicon oxide surfaces are used as the boiling surfaces. As the results of pool boiling experiments based on distilled water in ambient pressure condition, the CHF decreased as the length of the heater increased. By the high speed imaging, it was shown that the number of vapor columns increased as the length of the heater increased. Comparing the number of vapor columns and the CHF according to the heater length, the change in the CHF according to the heater length was analyzed based on the hydrodynamic instability.

• Journal of the Semiconductor & Display Technology
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• v.22 no.2
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• pp.35-39
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• 2023

Silicon oxide thin films have been deposited by plasma-enhanced chemical vapor deposition in SiH4 and N2O plasma along the variation of the gas flow ratio. Optical emission spectroscopy was employed to monitor the plasma and ellipsometry was employed to obtain refractive index of the deposited thin film. The atomic ratio of Si, O, and N in the film was obtained using XPS depth profiling. Fourier Transform Infrared Spectroscopy was used to analyze structures of the films. RI decreased with the increase in N2O/SiH4 gas flow ratio. We noticed the increase in the Si-O-Si bond angles as the N2O/SiH4 gas flow ratio increased, according to the analysis of the Si-O-Si stretching peak between 950 and 1,150 cm-1 in the wavenumber. We observed a correlation between the optical emission intensity ratio of (ISi+ISiH)/IO. The OES intensity ratio is also related with the measured refractive index and chemical composition ratio of the deposited thin film. Therefore, we report the added value of OES data analysis from the plasma related to the thin film characteristics in the PECVD process.

• Journal of the Semiconductor & Display Technology
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• v.22 no.4
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• pp.72-75
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• 2023

Carbon neutrality has been emerged as important mission for all the manufacturing industry to reduce energy usage and carbon emission equivalent. Korean semiconductor and display manufacturing industries are also in huge interest by minimize the energy usage as well as to find a less global warming product gases in both etch and cleaning. In addition, Korean government is also investing long term research and development plan for the safe environment in various ways. In this paper, we revisit previous research activities on carbon emission equivalent and current research activities performed in semiconductor process diagnosis research center at Myongji University with respect to the reduction of NF3 usage for the PECVD chamber cleaning, and we present the analytical result of the exhaust gas with residual gas analysis in both 6 inches and 12 inches PECVD equipment. The presented result can be a reference study of the development of new substitution gas in near future to compare the cleaning rate of the silicon oxide deposition chamber.