• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.114-114
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• 2011

We report a high-performance and air-stable flexible and invisible semiconductor which can be substitute for the n-type organic semiconductors. N-type organic-inorganic nanohybrid superlattices were developed for active semiconducting channel layers of thin film transistors at low temperature of $150^{\circ}C$ by using molecular layer deposition with atomic layer deposition. In these nanohybrid superlattices, self-assembled organic layers (SAOLs) offer structural flexibility, whereas ZnO inorganic layers provide the potential for semiconducting properties, and thermal and mechanical stability. The prepared SAOLs-ZnO nanohybrid thin films exhibited good flexibility, transparent in the visible range, and excellent field effect mobility (> 7cm2/$V{\cdot}s$) under low voltage operation (from -1 to 3V). The nanohybrid semiconductor is also compatible with pentacene in p-n junction diodes.

• ETRI Journal
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• v.27 no.4
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• pp.449-452
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• 2005

The electrical characteristics of solid state devices such as the bipolar junction transistor (BJT), metal-oxide semiconductor field-effect transistor (MOSFET), and other active devices are altered by impinging photon radiation and temperature in the space environment. In this paper, the threshold voltage, the breakdown voltage, and the on-resistance for two kinds of MOSFETs (200 V and 100 V of $V_{DSS}$) are tested for ${\gamma}-irradiation$ and compared with the electrical specifications under the pre- and post-irradiation low dose rates of 4.97 and 9.55 rad/s as well as at a maximum total dose of 30 krad. In our experiment, the ${\gamma}-radiation$ facility using a low dose, available at Korea Atomic Energy Research Institute (KAERI), has been applied on two commercially available International Rectifier (IR) products, IRFP250 and IRF540.

• Ceramist
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• v.21 no.1
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• pp.98-111
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• 2018

The lead-based perovskite (CH3NH3PbI3) material has a high molar coefficient, high crystallinity at low temperature, and long range of balanced electron-hole transport length. In addition, PCE of perovskite solar cells (PSCs) has been dramatically improved by over 22% by amending the electronic quality of perovskite and by using state-of-the-art hole transporting materials (HTMs) such as tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD) due to enhanced charge transport toward the electrode via properly aligned energy levels with respect to the perovskite. Replacing the spiro-OMeTAD with new HTMs with the desired properties of appropriate energy levels, high hole mobility in its pristine form, low cost, and easy processable materials is necessary for attaining highly efficient and stable PSCs, which are anticipated to be truly compatible for practical application. Furthermore, Recently Pb-free perovskite materials much attention as an alternative light-harvesting active layer material instead of lead based perovskite in photovoltaic cells. In this work, we demonstrate a Pb-free perovskite material for the light harvesting and emitter as optoelectronic devices.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.396-397
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• 2011

This paper has proposed a multi-channel low pass filter (LPF) for LTE-Advanced systems. The proposed LPF is an active-RC 5th chebyshev topology with three cut-off frequencies of 5 MHz, 10 MHz, and 40 MHz. A 3-bit tuning circuit has been adopted to prevent variations of each cut-off frequency from process, voltage, and temperature (PVT). To achieve a high cut-off frequency of 40 MHz, an operational amplifier used in the proposed filter has employed a PMOS cross-connection load with a negative impedance. A proposed filter has been implemented in a $0.13-{\mu}m$ CMOS technology and consumes 20.2 mW with a 1.2V supply voltage.

• Korean Journal of Materials Research
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• v.30 no.11
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• pp.615-620
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• 2020

Oxide semiconductor, represented by a-IGZO, has been commercialized in the market as active layer of TFTs of display backplanes due to its various advantages over a-Si. a-IGZO can be deposited at room temperature by RF magnetron sputtering process; however, additional thermal annealing above 300℃ is required to obtain good semiconducting properties and stability. These temperature are too high for common flexible substrates like PET, PEN, and PI. In this work, effects of microwave annealing time on IGZO thin film and associated thin-film transistors are demonstrated. As the microwave annealing time increases, the electrical properties of a-IGZO TFT improve to a degree similar to that during thermal annealing. Optimal microwave annealed IGZO TFT exhibits mobility, SS, V_th, and V_H of 6.45 ㎠/Vs, 0.17 V/dec, 1.53 V, and 0.47 V, respectively. PBS and NBS stability tests confirm that microwave annealing can effectively improve the interface between the dielectric and the active layer.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.520-527
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• 2020

Hwangtoh is the rich resource that accounts for about 15.0% of the domestic soil, and can be used as the admixture of concrete with Pozzolan characteristics if activated by rapidly freezing after burning with high temperature. In this study, the mortar curbs containing active hwangtoh were produced, based on the mixture for the mortar curbs sold on the market. The substitution rate of active hwangtoh were considered 10.0% and 25.0%, and the test items were selected to compressive and flexural strength tests, freezing/thawing resistance tests, accelerated carbonation tests, and accelerated chloride diffusion tests. In the results of the mechanical performance, it was showed that the highest strength was evaluated in OPC mixture, and the increase in strength was small by the increase of age, which was believed to be due to the fact that most of the strength in each mixture was created in three days of steam curing. The results of the freezing/thawing tests for 28 aged days showed the reduction rate of compressive strength was 85.0% or higher for all specimen, meeting the criteria presented. The accelerated carbonation tests were carried out on the specimen at 28 days of age, and the results showed that the mortar with active hwangtoh had lower carbonation resistance performance than mortar with OPC. The passed charge of each mixture was assessed in accordance with ASTM C 1202 on 28 and 91 aged days. The OPC mixture had "Low" rate and the mortar with active hwangtoh had "Moderate" rate. So it was thought that the mortar with active hwangtoh had appropriate resistance performance for chloride attack.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1116-1118
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• 2005

We studied laser crystallization of amorphous silicon films prepared at ultra low temperatures ($<150^{\circ}C$). Amorphous silicon films having a low content of hydrogen were deposited by using catalytic chemical vapor deposition method. Influence of process parameters on the hydrogen content was investigated. Laser crystallization was performed dispensing with the preliminary dehydrogenation process. Crystallization took place at a laser energy density value as low as $70\;mJ/cm^2$, and the grain size increased with increasing the laser energy. The ELA crystallization of Catalytic CVD a-Si film is a promising candidate for Poly-Si TFT in active-matrix flexible display on plastic substrates.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.235-242
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• 2017

A driving controller for active destruction protections can be applied to machinery, aerospace and military fields. In particular, this controller can be used to track and attack enemy flying objects through the active control. It is important to ensure reliability of the driving controller since its operation should be kept with precision to the target point. The temperature of the environment where the driving controller is used is about -32 C ~ 50 C (241~323 ). Heat generated in the driving controller should be maintained below a certain threshold (85 C (358 )) to ensure reliability; therefore, the study and analysis of the heat flow characteristics in the driving controller are required. In this research, commercial software Solid-Works Flow Simulation was used for the numerical simulation assuming a low Reynolds number turbulence model and an incompressible viscous flow. The goal of this paper is to design the driving controller safely by analyzing the characteristics of the heat flow inside of the controller composed of chips or boards. Our analysis shows temperature distributions for boards and chips below a certain threshold.

• Applied Chemistry for Engineering
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• v.22 no.3
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• pp.308-311
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• 2011

The reaction mechanism of selective catalytic reduction of NOx over sewage sludge char impregnated with MnOx using $NH_3$ as the reducing agent was investigated. The active Mn phase was shown to be $Mn_3O_4$ from the XRD analysis. Adsorption was the dominant NOx removal mechanism at low temperatures below $150^{\circ}C$ although reduction reaction also contributed partly to the NOx removal at $100{\sim}150^{\circ}C$. The reaction rate constants of NOx removal over non-impregnated and MnOx-impregnated active chars were compared based on experimental results. The MnOx-impregnated char was shown to have a higher reaction rate constant and a higher NOx removal efficiency due to a higher collision coefficient and a lower activation energy. The activation energy for both chars was shown to be relatively low (10~12 kJ/mol) under the experimental conditions of this study.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.377-377
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• 2011

Organic solar cells (OSCs) with low cost have been studied to apply on flexible substrate by solution process in low temperature [1]. In previous researches, conventional organic solar cell was composed of metal oxide anode, buffer layer such as PEDOT:PSS, photoactive layer, and metal cathode with low work function. In this structure, indium tin oxide (ITO) and Al was generally used as metal oxide anode and metal cathode, respectively. However, they showed poor reliability, because PEDOT:PSS was sensitive to moisture and air, and the low work function metal cathode was easily oxidized to air, resulting in decreased efficiency in half per day [2]. Inverted organic solar cells (IOSCs) using high work function metal and buffer layer replacing the PEDOT:PSS have focused as a solution in conventional organic solar cell. On the contrary to conventional OSCs, ZnO and TiO2 are required to be used as a buffer layer, since the ITO in IOSC is used as cathode to collect electrons and block holes. The ZnO is expected to be excellent electron transport layer (ETL), because the ZnO has the advantages of high electron mobility, stability in air, easy fabrication at room temperature, and UV absorption. In this study, the IOSCs based on poly [N-900-hepta-decanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzothiadiazole)] (PCDTBT) : [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) were fabricated with the ZnO electron-transport layer and MoO3 hole-transport layer. Thickness of the ZnO for electron-transport layer was controlled by rotation speed in spin-coating. The PCDTBT and PC70BM were mixed with a ratio of 1:2 as an active layer. As a result, the highest efficiency of 2.53% was achieved.