• Journal of the Semiconductor & Display Technology
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• v.18 no.4
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• pp.12-17
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• 2019

In this study, the Ag nano-dots structure and silicon nitride film were applied to the textured wafer surface to improve the light trapping effect of mono-crystalline silicon solar cell. Ag nano-dots structure was formed by performing a heat treatment for 30 minutes at 650℃ after the deposition of 10nm Ag thin film. Ag thin film deposition was performed using a thermal evaporator. The silicon nitride film was deposited by a Hot-wire chemical vapor deposition. The effect of light trapping was compared and analyzed through light reflectance measurements. Experimental results showed that the reflectivity increased by 0.5 ~ 1% under all nitride thickness conditions when Ag nano-dots structure was formed before nitride film deposition. In addition, when the Ag nano-dots structure is formed after deposition of the silicon nitride film, the reflectance is increased in the nitride film condition of 70 nm or more. When the HF treatment was performed for 60 seconds to improve the Ag nano-dot structure, the overall reflectance was improved, and the reflectance was 0.15% lower than that of the silicon nitride film-only sample at 90 nm silicon nitride film condition.

• Journal of the Optical Society of Korea
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• v.18 no.3
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• pp.256-260
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• 2014

Columnar-structured cesium iodide (CsI) scintillators doped with thallium (Tl) are frequently used as x-ray converters in medical and industrial imaging. In this study we investigated the imaging characteristics of CsI:Tl films with various reflective layers-aluminum (Al), chromium (Cr), and titanium dioxide ($TiO_2$) powder-coated on glass substrates. We used two effusion-cell sources in a thermal evaporator system to fabricate CsI:Tl films on substrates. The scintillators were observed via scanning electron microscopy (SEM), and scintillation characteristics were evaluated on the basis of the emission spectrum, light output, light response to x-ray dose, modulation transfer function (MTF), and x-ray images. Compared to control films without a reflective layer, CsI:Tl films with reflective layers showed better sensitivity and light collection efficiency, and the film with a $TiO_2$ reflective layer showed the best properties.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.31-36
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• 2021

Recently, automobile air conditioning systems have applied an alternative refrigerant that can replace the high GWP refrigerant R134a due to the global warming problem. This study simulated the performance of an automobile climate control system with an internal heat exchanger and TXV. Refrigerant R1234yf was applied as the working fluid. Amesim, a commercial software program, was used to model the main components of the compressor, condenser, TXV, evaporator, and internal heat exchanger. As the outside temperature increased from 30℃ to 40℃, the cooling capacity of the system decreased by 3.1%, and the power consumption of the compressor increased by 17.1%. In addition, The performance characteristics of the refrigeration cycle were simulated by increasing the fin pitch of the condenser from 0.8 mm to 1.4 mm. When the fin pitch was larger than 1.0 mm, the condenser capacity decreased, and the system COP was lowered by 5.9%. When the fin pitch of the condenser was 0.8 mm, which was smaller than 1.0 mm, there was no significant change in the system performance. Hence, the optimal performance was observed at a fin pitch of 1.0 mm.

• Korean Journal of Metals and Materials
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• v.48 no.2
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• pp.133-140
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• 2010

10 nm thick Ni layers were deposited on 200 nm $SiO_2/Si$ substrates using an e-beam evaporator. Then, 60 nm or 20 nm thick ${\alpha}$-Si:H layers were grown at low temperature (<$200^{\circ}C$) by a Catalytic-CVD. NiSi layers were already formed instantaneously during Cat-CVD process regardless of the thickness of the $\alpha$-Si. The resulting changes in sheet resistance, microstructure, phase, chemical composition, and surface roughness with the additional rapid thermal annealing up to $500^{\circ}C$ were examined using a four point probe, HRXRD, FE-SEM, TEM, AES, and SPM, respectively. The sheet resistance of the NiSi layer was 12${\Omega}$/□ regardless of the thickness of the ${\alpha}$-Si and kept stable even after the additional annealing process. The thickness of the NiSi layer was 30 nm with excellent uniformity and the surface roughness was maintained under 2 nm after the annealing. Accordingly, our result implies that the low temperature Cat-CVD process with proposed films stack sequence may have more advantages than the conventional CVD process for nano scale NiSi applications.

• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.255-259
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• 2022

Solar membrane steam generation is a very promising technology that can harvest purified water from seawater or wastewater during the current danger of running out of pure water. However, solar Membrane steam generation had direct contact with water, making it difficult to increase the efficient amount of evaporation. Here, we propose solar membrane steam generator composed of polydimethylsiloxane (PDMS) and graphene oxide (GO) and improved evaporation through wettability control in part throughout the water-absorbing membrane. Wettability control has shown significant improvements in thermal localization and temperature rise in the area of heat exchange with sunlight. The evaporator has an evaporation rate of 1.54 kg m^-2 h^-1 under 1 sun irradiation. The results showed that Solar membrane steam evaporation can effectively harvest pure water through an increase in evaporation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.6
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• pp.449-469
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• 2011

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering during 2010. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) Research trends of thermal and fluid engineering have been surveyed as groups of general thermal and fluid flow, fluid machinery, and new and renewable energy. Various topics were presented in the field of general thermal and fluid flow. Research issues mainly focused on the thermal reliability of axial fan and compressor in the field of fluid machinery. Studies on the design of ground source heat pump systems and solar chemical reactors were executed in the field of new and renewable energy. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer in thermoelectric cooling/power generation systems, combined heat and power systems, carbon nano fluid with PVP, channel filled with metal foam and smoke ventilation in a rescue station of a railroad tunnel. Also the studies on flow boiling of R123/oil mixture in a plain tube bundle and R410A charge amount in an air cooled mini-channel condenser were reported. In the area of industrial heat exchangers, researches on plate heat exchanger, shell and tube heat exchanger, enthalpy exchanger, micro channel PCHE were performed. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer in thermoelectric cooling/power generation systems, combined heat and power systems, carbon nano fluid with PVP, channel filled with metal foam and smoke ventilation in a rescue station of a railroad tunnel. Also the studies on flow boiling of R123/oil mixture in a plain tube bundle and R410A charge amount in an air cooled mini-channel condenser were reported. In the area of industrial heat exchangers, researches on plate heat exchanger, shell and tube heat exchanger, enthalpy exchanger, micro channel PCHE were performed. (3) Refrigeration systems with alternative refrigerants such as hydrocarbons, mixed refrigerants, and CO2 were studied. Performance improvement of refrigeration systems are tried applying various ideas of refrigerant subcooling, dual evaporator with hot gas bypass control and feedforward control. The hybrid solar systems combining the solar collection devices with absorption chillers or compression heat pumps are simulated and studied experimentally as well to improve the understanding and the feasibility for actual applications. (4) Research trend in the field of mechanical building facilities has been found to be mainly focused on field applications rather than performance improvements. Various studies on heating and cooling systems, HVAC facilities, indoor air environments and energy resources were carried to improve the maintenance and management of building service equipments. In the field of heating and cooling systems, papers on a transformer cooling system, a combined heat and power, a slab thermal storage and a heat pump were reported. In the field of HVAC facilities, papers on a cooling load, an ondol and a drying were presented. Also, studies on HVAC systems using unutilized indoor air environments and energy resources such as air curtains, bioviolence, cleanrooms, ventilation, district heating, landfill gas were studied. (5) In the field of architectural environment and energy, studies of various purposes were conducted such as indoor environment, building energy, renewable energy and green building. In particular, renewable energy and building energy-related researches have mainly been studied reflecting the global interest. In addition, many researches which related the domestic green building certification of school building were performed to improve the indoor environment of school.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.1
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• pp.46-52
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• 2011

A study on the improvement for cycle efficiency of closed-type ocean thermal energy conversion (OTEC) was studied to obtain the basic data for the optimal design of cycle. For that, OTEC cycle with a generator, a reheater and a multi-turbine was simulated and analyzed. The basic thermodynamic model for OTEC is Rankine cycle and the surface seawater of $26^{\circ}C$ and deep seawater of $5^{\circ}C$ were used for the heat source of evaporator and condenser, respectively. Ammonia is used as the working fluid. The cycle efficiency increased when generator is added with 0.9 generator effectiveness. When the reheater and multi-turbine are applied in the basic cycle, the cycle efficiency showed 3.14% and the capacity of heat exchanger decreased for same total cycle power. For the OTEC cycle with the generator, the reheater and the multi-turbine showed the highest cycle efficiency and increased the efficiency by more than 6.5% comparing with the basic OTEC cycle.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.2037-2042
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• 2013

A TCO-less palladium (Pd) catalytic layer on the glass substrate was assessed as the counter electrode (CE) in a dye sensitized solar cell (DSSC) to confirm the stability of Pd with the $I^-/I_3{^-}$electrolyte on the DSSC performance. A 90nm-thick Pd film was deposited by a thermal evaporator. Finally, DSSC devices of $0.45cm^2$ with glass/FTO/blocking layer/$TiO_2$/dye/electrolyte(10 mM LiI + 1 mM $I_2$ + 0.1 M $LiClO_4$ in acetonitrile solution)/Pd/glass structure was prepared. We investigated the microstructure and photovoltaic property at 1 and 12 hours after the sample preparation. The optical microscopy, field emission scanning electron microscopy (FESEM), cyclic voltammetry measurement (C-V), and current voltage (I-V) were employed to measure the microstructure and photovoltaic property evolution. Microstructure analysis showed that the corrosion by reaction between the Pd layer and the electrolyte occurred as time went by, which led the decrease of the catalytic activity and the efficiency. I-V result revealed that the energy conversion efficiency after 1 and 12 hours was 0.34% and 0.15%, respectively. Our results implied that we might employ the other non-$I^-/I_3{^-}$electrolyte or the other catalytic metal layers to guarantee the long term stability of the DSSC devices.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.303-310
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• 2008

We fabricated hydrogenated amorphous silicon(a-Si:H) 140 nm thick film on a $180\;nm-SiO_2/Si$ substrate with an inductively-coupled plasma chemical vapor deposition(ICP-CVD) equipment at $250^{\circ}C$. Moreover, 30 nm-Ni film was deposited with a thermal-evaporator sequently. Then the film stack was annealed to induce silicides by a rapid thermal annealer(RTA) at $200{\sim}500^{\circ}C$ in every $50^{\circ}C$ for 30 minuets. We employed a four-point tester, high resolution X-ray diffraction(HRXRD), field emission scanning electron microscope(FE-SEM), transmission electron microscope(TEM), and scanning probe microscope(SPM) in order to examine the sheet resistance, phase transformation, in-plane microstructure, cross-sectional microstructure evolution, and surface roughness, respectively. We confirmed that nano-thick high resistive $Ni_3Si$, mid-resistive $Ni_2Si$, and low resistive NiSi phases were stable at the temperature of <300, $350{\sim}450^{\circ}C$, and >$450^{\circ}C$, respectively. Through SPM analysis, we confirmed the surface roughness of nickel silicide was below 12 nm, which implied that it was superior over employing the glass and polymer substrates.

• Journal of the Korean Vacuum Society
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• v.21 no.4
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• pp.205-211
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• 2012

We investigated the optical and hydrophobic properties of the deposited silver (Ag) zinc oxide (ZnO) nanorods (NRs) on flexible indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates (i.e., ITO/PET). The ZnO NRs were grown by an electrochemical deposition using a sputtered ZnO seed layer and the Ag was deposited by using a thermal evaporator. For comparison, the same fabrication process was carried out on the bare ITO/PET without ZnO NRAs. Due to the discrete surface of ZnO NRs, the deposited Ag was formed as nano-scale particles, while the Ag became film-like for bare ITO/PET. In order to control the size and amount of Ag particles, the Ag deposition time was changed from 100 to 600 s. When the deposition time was increased, the Ag particles became larger and denser, and the absorptance was increased. This enhanced absorptance may be due to the localized surface plasmon resonance of Ag particles. Furthermore, the relatively high hydrophobicity was observed for the deposited Ag on the ZnO NRs/ITO/PET. These improved optical and surface properties are expected to be useful for flexible photovoltaic and optoelectronic devices.