• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.5
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• pp.169-174
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• 2022

This study is to verify the feasibility of SiC single crystal growth using recycled SiC powder. The fundamental physical properties such as particle size, shape, composition and impurities of the recycled powder were analyzed, and the sublimation behavior occurring inside the reactor were predicted using the basic data. As a result of comprehensive judgment, the physical properties of the recycled powder were suitable for single crystal growth, and single crystal growth experiments were conducted using this. 100 mm 4H-SiC single crystal ingot with a height of 25 mm was grown without polytype inclusion. In the case of micro-pipe density was 0.02 ea/cm² and resistivity characteristics was 0.015~0.020 ohm·cm², commercial level quality was obtained, but additional analysis related to dislocation density and stacking faults is required for device application.

• The Journal of the Korea Contents Association
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• v.21 no.12
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• pp.918-925
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• 2021

The perovskite solar cell is a next-generation solar cell that replaces the existing silicon solar cell. It is a solar cell device using an organic-inorganic hybrid material having a perovskite structure as a photoactive layer. It has advantages for the process and has shown rapid efficiency improvement over the past decade. In the process of commercialization of such perovskite solar cells, research and development for a large-area coating method should be carried out. As one of the large-area perovskite solar cell large-area coating methods, the slot-die coating method was studied. By using a meniscus to pass over the substrate and coating the solution, the 3D printer was equipped with a meniscus so that it could be coated. Variables that act during coating include bed temperature, coating speed, N₂ blowing interval, N₂ blowing height, N₂ blowing intensity, etc. By controlling these, the perovskite absorption layer was manufactured and the coating conditions for manufacturing large-area devices were optimized.

• Transactions on Electrical and Electronic Materials
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• v.1 no.4
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• pp.11-15
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• 2000

This paper presents a process optimization of antireflection (AR) coating on crystalline Si solar cells. Theoretical and experimental investigations were performed on a double-layer AR(DLAR) coating of MgFe$_2$/GeO$_2$. We investigated GeO$_2$ films as an AR layer because they have a proper refractive index of 2.46 and demonstrate the same lattice constant as Si substrate. RF sputter grown GeO$_2$ film showed deposition temperature strong dependence. The GeO$_2$ at 400$\^{C}$ exhibited a strong (111) preferred orientation and the lowest surface roughness of 6.87 $\AA$. Refractive index of MgFe$_2$film was measured as 1.386 for the most of growth temperature. An optimized DLAR coating showed a reflectance as low as 2.04% in the wavelengths ranged from 0.4 ㎛ to 1.1 ㎛. Solar cells with a structure of MgFe$_2$/GeO$_2$/Ag/N$\^$+//p-type Si/P$\^$+//Al were investigated with the without DLAR coatings. We achieved the efficiency of solar cells greater than 15% with 3.12% improvement with DLAR coatings. Further details about MgFe$_2$,GeO$_2$ films, and cell fabrication parameters are presented in this paper.

• Journal of IKEEE
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• v.27 no.1
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• pp.19-24
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• 2023

Since silicon having a band gap energy of about 1.12 eV are limited to a maximum operating temperature of less than 250 ℃, the sample with MIS structure based on the SiC substrate of wide-band gap energy was manufactured and the hydrogen response characteristics at high temperatures were investigated. The dielectric layer applied here is a tantalum oxide layer that is highly permeable to hydrogen gas and shows stability at high temperatures. It was formed by RTO at a temperature of 900 ℃ with tantalum. The thickness, depth profiles, and leakage current of the tantalum oxide layer were analyzed through TEM, SIMS, and leakage current characteristics. For the hydrogen gas response characteristics, the capacitance change characteristics were investigated in the temperature range from room temperature to 400 ℃ for hydrogen gas concentrations from 0 to 2,000 ppm. As a result, it was confirmed that the sample exhibited excellent sensitivity and a response time of about 60 seconds.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.12
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• pp.8-13
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• 2001

Cerium oxide ($CeO_2$) thin film has been proposed as a buffer layer between the ferroelectric thin film and the Si substrate in Metal-Ferroelectric-Insulator-Silicon (MFIS) structures for ferroelectric random access memory (FRAM) applications. In this study, $CeO_2$ thin films were etched with $Cl_2$/Ar gas mixture in an inductively coupled plasma (ICP). Etch properties were measured for different gas mixing ratio of $Cl_2$($Cl_2$+Ar) while the other process conditions were fixed at RF power (600 W), dc bias voltage (-200 V), and chamber pressure (15 mTorr). The highest etch rate of $CeO_2$ thin film was 230 ${\AA}$/min and the selectivity of $CeO_2$ to $YMnO_3$ was 1.83 at $Cl_2$($Cl_2$+Ar gas mixing ratio of 0.2. The surface reaction of the etched $CeO_2$ thin films was investigated using x-ray photoelectron spectroscopy (XPS) analysis. There is a Ce-Cl bonding by chemical reaction between Ce and Cl. The results of secondary ion mass spectrometer (SIMS) analysis were compared with the results of XPS analysis and the Ce-Cl bonding was monitored at 176.15 (a.m.u). These results confirm that Ce atoms of $CeO_2$ thin films react with chlorine and a compound such as CeCl remains on the surface of etched $CeO_2$ thin films. These products can be removed by Ar ion bombardment.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.4
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• pp.83-89
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• 2015

In this paper, we propose a fabrication technique for enhanced electrical properties of piezoelectric thick films with excellent patterning property using sol-infiltration and a direct-patterning process. To achieve the needs of high-density and direct-patterning at a low sintering temperature (< $850^{\circ}C$), a photosensitive lead zirconate titanate (PZT) solution was infiltrated into a screen-printed thick film. The direct-patterned PZT films were clearly formed on a locally screen-printed thick film, using a photomask and UV light. Because UV light is scattered in the screen-printed thick film of a porous powder-based structure, there are needs to optimize the photosensitive PZT sol infiltration process for obtaining the enhanced properties of PZT thick film. By optimizing the concentration of the photosensitive PZT sol, UV irradiation time, and solvent developing time, the hybrid films prepared with 0.35 M of PZT sol, 4 min of UV irradiation and 15 sec solvent developing time, showed a very dense with a large grain size at a low sintering temperature of $800^{\circ}C$. It also illustrated enhanced electrical properties (remnant polarization, $P_r$, and coercive field, $E_c$). The $P_r$ value was over four times higher than those of the screen-printed films. These films integrated on silicon wafer substrate could give a potential of applications in micro-sensors and -actuators.

• Journal of Periodontal and Implant Science
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• v.47 no.2
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• pp.116-131
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• 2017

Purpose: The entry of bacteria or harmful substances through the epithelial seal of human gingival keratinocytes (HGKs) in the junctional epithelium (JE) is blocked by specialized intercellular junctions such as E-cadherin junctions (ECJs). However, the influence of roughened substrates, which may occur due to apical migration of the JE, root planing, or peri-implantitis, on the development of the ECJs of HGKs remains largely unknown. Methods: HGKs were cultured on substrates with varying levels of roughness, which were prepared by rubbing hydrophobic polystyrene dishes with silicon carbide papers. The activity of c-Jun N-terminal kinase (JNK) was inhibited with SP600125 or by transfection with JNK short hairpin RNA. The development of intercellular junctions was analyzed using scanning electron microscopy or confocal laser scanning microscopy after immunohistochemical staining of the cells for E-cadherin. The expression level of phospho-JNK was assessed by immunoblotting. Results: HGKs developed tight intercellular junctions devoid of wide intercellular gaps on smooth substrates and on rough substrates with low-nanometer dimensions (average roughness $[Ra]=121.3{\pm}13.4nm$), although the ECJs of HGKs on rough substrates with low-nanometer dimensions developed later than those of HGKs on smooth substrates. In contrast, HGKs developed short intercellular junctions with wide intercellular gaps on rough substrates with mid- or high-nanometer dimensions ($Ra=505.3{\pm}115.3nm$, $867.0{\pm}168.6nm$). Notably, the stability of the ECJs was low on the rough substrates, as demonstrated by the rapid destruction of the cell junction following calcium depletion. Inhibition of JNK activity promoted ECJ development in HGKs. JNK was closely associated with cortical actin in the regulation of ECJs in HGKs. Conclusions: These results indicate that on rough substrates with nanometer dimensions, the ECJs of HGKs develop slowly or defectively, and that this effect can be reversed by inhibiting JNK.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.5
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• pp.224-230
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• 2001

The characteristics of $NO/N_2O$ annealed reoxidized nitrided oxide being studied as super thin gate oxide and gate dielectric layers of Non-Volatile Semiconductor Memory (NVSM) were investigated by Dynamic Secondary Ion Mass Spectrometry (D-SIMS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), and Auger Electron Spectroscopy (AES). The specimen was annealed by $NO/N_2O$ after initial oxide process and then rcoxidized for nitrogen redistribution in nitrided oxide. Out-diffusion of incorporated nitrogen during the wet oxidation in reoxidation process took place more strongly than that of the dry oxidation. It seems to indicate that hydrogen plays a role in breaking the Si N bonds. As reoxidation proceeds, incorporated nitrogen of $NO/N_2O$ annealed nitrided oxide is obsen-ed to diffuse toward the surface and substrate at the same time. ToF-SIMS results show that SiON species are detected at the initialoxide interface, and Si,NO species near the new $Si_2NO$ interface that formed after reoxidation. These SiON and $Si_2NO$ species most likely to relate to the origin of the state of memory charge traps in reoxidized nitrided oxide, because nitrogen dangling bonds of SiON and silicon dangling bonds of $Si_2NO$ are contained defects associated with memory effect.

• Journal of Sensor Science and Technology
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• v.11 no.6
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• pp.342-349
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• 2002

New formation technique of metal oxide sensing film was proposed m this paper. Silicon wafer with Pt electrodes was used as a substrate for depositing metal Sn film. Metal Sn was deposited in the state of not continuous film but only island state. The samples were prepared to obtain the optimal condition of metal Sn deposition. The resistances of deposited Sn onto Pt electrodes amounted to $1\;k{\Omega}$, $5\;k{\Omega}$, $10\;k{\Omega}$ and $50\;k{\Omega}$, respectively. Also The sample with $1,500\;{\AA}$ thickness of Sn was prepared m order to compare sensing properties between conventional type and proposing type. After deposition of metal Sn, $SnO_2$ was formed by thermal oxidation method for 3 hrs. in $O_2$ ambient at $700^{\circ}C$. Surface morphology, crystal structure and surface roughness of oxidized-sensing film were examined by SEM, XRD, and AFM, respectively. From the results of these analyses, the optimal deposition condition of Sn was that the Pt electrode resistance became $10\;k{\Omega}(300\;{\AA})$. Also, the sensing characteristics of fabricated sensing film for various concentrations of butane, propane and carbon monoxide gases were measured at he operating temperatures of $250^{\circ}C$, $300^{\circ}C$ and $350^{\circ}C$, respectively. Although catalyst as not added to the sensing film, it has exhibited the high sensitivity to all the test gases.

• Journal of the Korean Vacuum Society
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• v.15 no.1
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• pp.37-44
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• 2006

The homoepitaxy of Si(5 5 12) at $495^{\circ}C$ has been studied by Scanning Tunneling Microscopy under ultrahigh vacuum. A Si-dimer is the basic building-block and preferentially adsorbs on a unique site, that is, the Si-dimer/adatom site at the (337) and the (225) subsections within the Si(5 5 12) unit cell. The Si(5 5 12) unit cell is faceted to $3\times(337)$ subsections filled with Si-addimers and $1\times(113)$ subsection. In this step the tetramer at the other (337) section within the unit cell is transformed to a dimer/adatom site which can accept Si-dimers. Each (337) section is faceted to $1\times(112)\;and\;1\times(113)$, and then finally the unit cell of Si(5 5 12) is faceted to $3\tiems(112)\;and\;4\times(113)$ and forms the facet of effective height, $2.34{\AA}$. In this step, mutual transformation between the honeycomb chain and the dimer/adatom occurs. Finally, the valley between (112) and (113) facets is filled. If once the last step is completed, the uniform and planar Si(5 5 12) terrace is recovered. From the present study, therefore, it can be concluded that the homoepitaxy on Si(5 5 12) is periodically achieved and such growth mode is quite unique since faceting of the substrate-unit-cell plays a critical role for controlling uniformity of the overlayer.