• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.77-78
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• 2006

We fabricated photonic crystals on GaAs and GaN substrates. After anodizing the aluminium thin film in electrochemical embient, the porous alumina was implemented to the mask for reactive ion beam etching process of GaAs wafer. And photonic crystals in GaN wafer were also fabricated using electron beam nano-lithography process. The coated PMMA thin film with 200 nm-thickness on GaN surface was patterned with triangular lattice and etched out the GaN surface by the inductively coupled plasma source. The fabricated GaAs and GaN photonic crystals provide the enhanced intensities of light emission for the wavelengths of 858 and 450 nm, respectively. We will present the detailed dimensions of photonic crystals from SEM and AFM measurements.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.12
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• pp.674-678
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• 2013

We present a non-invasive technique to the measure temperature distribution in nano-sized porous thin films by means of the two-color laser-induced fluorescence (2-LIF) of rhodamine B. The fluorescence induced by the green line of a mercury lamp with the makeup of optical filters was measured on two separate color bands. They can be selected for their strong difference in the temperature sensitivity of the fluorescence quantum yield. This technique allows for absolute temperature measurements by determining the relative intensities on two adequate spectral bands of the same dye. To measure temperature fields, Silica (SiO2) nanoporous structure with 1-um thickness was constructed on a cover glass, and fluorescent dye was absorbed into these porous thin films. The calibration curves of the fluorescence intensity versus temperature were measured in a temperature range of $10-60^{\circ}C$, and visualization and measurement of the temperature field were performed by taking the intensity distributions from the specimen for the temperature field.

• Korean Journal of Materials Research
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• v.18 no.10
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• pp.529-534
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• 2008

The hydrogen gas sensing properties of a zinc oxide nanowire structure were studied. Porous zinc oxide nanowire structures were fabricated by oxidizing zinc deposited on a single-wall carbon nanotube (SWNT) template. This revealed a porous ZnO-SWNT composite due to the porosity in the SWNT film. The gas sensing properties were compared with those of zinc oxide thin films deposited on SiO2/Si substrates in sensitivity and operating temperature. The composite structure showed higher sensitivity and lower operating temperature than the zinc oxide film. It showed a response even at room temperature while the film structure did not.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1388-1390
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• 2007

This paper investigates how various concentrations of lithium ion influence on crystallization of MgO in thin films formed by spin coating and an the discharge characteristic in a flat fluorescent lamp structure. The XRD results indicate $Li^+$ ion enhances the growth of MgO crystal in a spin coated thin film. The discharge property with the $Li^+$ ion doped MgO films show the lithium ion in MgO film clearly reduce the initial discharge voltages of test devices. Interestingly, the test panels with various doped MgO film have somewhat higher static memory margin of than that of pure-MgO owing probably to the pore structure of spin coated MgO films. The CL spectra, which confirm that the doping creates defects energy levels in the band gap of MgO, show the $F^+$ center is the main defects in doped MgO films.

• Korean Journal of Materials Research
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• v.25 no.12
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• pp.708-712
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• 2015

This study reports the effects of $H_2S$ gas concentration on the properties of $Cu_2ZnSnS_4(CZTS)$ thin films. Specifically, sulfurization process with low $H_2S$ concentrations of 0.05% and 0.1%, along with 5% $H_2S$ gas, was studied. CZTS films were directly synthesized on Mo/Si substrates by chemical bath deposition method using copper sulfate, zinc sulfate heptahydrate, tin chloride dihydrate, and sodium thiosulfate pentahydrate. Smooth CZTS films were grown on substrates at optimized chemical bath deposition condition. The CZTS films sulfurized at low $H_2S$ concentrations of 0.05 % and 0.1% showed very rough and porous film morphology, whereas the film sulfurized at 5% $H_2S$ yielded a very smooth and dense film morphology. The CZTS films were fully crystallized in kesterite crystal form when they were sulfurized at $500^{\circ}C$ for 1 h. The kesterite CZTS film showed a reasonably good room-temperature photoluminescence spectrum that peaked in a range of 1.4 eV to 1.5 eV, consistent with the optimal bandgap for CZTS solar cell applications.

• Journal of the Korean institute of surface engineering
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• v.49 no.3
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• pp.286-300
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• 2016

Pd-Ag alloy membranes have attracted a great deal of attention for their use in hydrogen purification and separation due to their high theoretical permeability, infinite selectivity and chemical compatibility with hydro-carbon containing gas streams. For commercial application, Pd-based membranes for hydrogen purification and separation need not only a high perm-selectivity but also a stable long-term durability. However, it has been difficult to fabricate thin, dense Pd-Ag alloy membranes on a porous stainless steel metal support with surface pores free and a stable diffusion barrier for preventing metallic diffusion from the porous stainless steel support. In this study, thin Pd-Ag alloy membranes were prepared by advanced Pd/Ag/Pd/Ag/Pd multi-layer sputter deposition on the modified porous stainless steel support using rough polishing/$ZrO_2$ powder filling and micro-polishing surface treatment, and following Ag up-filling heat treatment. Because the modified Pd-Ag alloy membranes using rough polishing/$ZrO_2$ powder filling method demonstrate high hydrogen permeability as well as diffusion barrier efficiency, it leads to the performance improvement in hydrogen perm-selectivity. Our membranes, therefore, are expected to be applicable to industrial fields for hydrogen purification and separation owing to enhanced functionality, durability and metal support/Pd alloy film integration.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.645-649
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• 2009

Liquid desiccant cooling technology can supply cooling by using waste heat and solar heat which are hard to use effectively. For compact and efficient design of a dehumidifier, it is important to sustain sufficient heat and mass transfer surface area for water vapor diffusion from air to liquid desiccant on heat exchanger. In this study, the plate type heat exchanger is adopted which has extended surface, and hydrophilic coating and porous layer coating are adopted to enhance surface wettedness. PP(polypropylene) plate is coated by porous layer and PET(polyethylene terephthalate) non-woven fabric is coated by hydrophilic polymer. These coated surfaces have porous structure, so that falling liquid film spreads widely on the coated surface foaming thin liquid film by capillary force. The temperature of liquid desiccant increases during dehumidification process by latent heat absorption, which leads to loss of dehumidification capacity. Liquid desiccant is cooled by cooling water flowing in plate heat exchanger. On the plate side, the liquid desiccant can be cooled by internal cooling. However the liquid desiccant on extended surface should be moved and cooled at heat exchanger surface. Optimal mixing and distribution of liquid desiccant between extended surface and plate heat exchanger surface is essential design parameter. The experiment has been conducted to verify effective surface treatment and distribution characteristics by measuring wall side flow rate and visualization test. It is observed that hydrophilic and porous layer coating have excellent wettedness, and the distribution can be regulated by adopting holes on extended surface.

• Korean Journal of Materials Research
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• v.20 no.11
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• pp.600-605
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• 2010

In order to meet the requirements of faster speed and higher packing density for devices in the field of semiconductor manufacturing, the development of Cu/Low k device material is explored for use in multi-layer interconnection. SiOC(-H) thin films containing alkylgroup are considered the most promising among all the other low k candidate materials for Cu interconnection, which materials are intended to replace conventional Al wiring. Their promising character is due to their thermal and mechanical properties, which are superior to those of organic materials such as porous $SiO_2$, SiOF, polyimides, and poly (arylene ether). SiOC(-H) thin films containing alkylgroup are generally prepared by PECVD method using trimethoxysilane as precursor. Nano voids in the film originating from the sterichindrance of alkylgroup lower the dielectric constant of the film. In this study, methyltriphenylsilane containing bulky substitute was prepared and characterized by using NMR, single-crystal X-ray, GC-MS, GPC, FT-IR and TGA analyses. Solid-state NMR is utilized to investigate the insoluble samples and the chemical shift of $^{29}Si$. X-ray single crystal results confirm that methyltriphenylsilane is composed of one Si molecule, three phenyl rings and one methyl molecule. When methyltriphenylsilane decomposes, it produces radicals such as phenyl, diphenyl, phenylsilane, diphenylsilane, triphenylsilane, etc. From the analytical data, methyltriphenylsilane was found to be very efficient as a CVD or PECVD precursor.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.589-594
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• 1997

Superconducting $YBa_2Cu_3O_y$ thin films were prepared at the deposition temperature of $650^{\circ}C$ under oxygen partial pressure of 0.0126 Torr on Si(111) and SrTiO3(100) substrates by chemical vapor deposition technique using $\beta$-diketonates of Y, Ba and Cu as source materials. The thin film fabricated on $SrTiO_3(100)$ had a $T_{c,onset}$ of 91K and $T_{c.0}$ of 87K. The thin film prepared on Si(111) had a $T_{c,onset}$ of 91K but didn't have a $T_{c.0}$ at liquid nitrogen boiling point(77.3K). Dense and two-dimensionally well alligned microstructure was developed for the film deposited on $SrTiO_3(100)$ substrate whereas a relatively porous and randomly distributed microstructure was developed for the film prepared on Si(111) substrate.

• Applied Chemistry for Engineering
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• v.24 no.4
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• pp.438-442
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• 2013

In the present work, electroless plating was used for coating thin films consisting mainly of Ni and P on carbon fiber. Structural changes appeared upon the post-annealing at various temperatures of the Ni-P film on carbon fiber was studied using various analysis methods. Scanning, a flat surface structure of Ni-P film on carbon fiber was found after electroless plating of Ni-P film on carbon fiber without post-annealing, whereas annealing at $350^{\circ}C$ resulted the formation of porous structures. With increasing the annealing temperature to $650^{\circ}C$ with an interval of $50^{\circ}C$, the pore size increased, but the density decreased. X-ray diffraction (XRD) showed the existence of metallic Ni, and Ni-P compounds before post-annealing, whereas the post-annealing resulted in the appearance of NiO peaks, and the decrease in the intensity of the peak of metallic Ni. Using X-ray photoelectron spectroscopy (XPS), phosphorous oxides were detected on the surface upon annealing at $650^{\circ}C$, and $700^{\circ}C$, which can be attributed to the phosphorous compounds originally existing in the deeper layers of the Ni films, which undergo sublimation and escape from the film upon annealing. Escape of phosphorous species from the bulk of Ni-P film upon annealing could leave a porous structure in the Ni films. Porous materials can be of potential applications in diverse fields due to their interesting physical properties such as high surface area, and methods for fabricating porous Ni films introduced here could be easily applied to a large-scale production, and therefore applicable in diverse fields such as environmental filters.