• 한국재료학회지
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• 제21권2호
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• pp.115-119
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• 2011

Si Nanowire (NW) field effect transistors (FETs) were fabricated on hard Si and flexible polyimide (PI) substrates, and their electrical characteristics were compared. Si NWs used as channels were synthesized by electroless etching method at low temperature, and these NWs were refined using a centrifugation method to get the NWs to have an optimal diameter and length for FETs. The gate insulator was poly(4-vinylphenol) (PVP), prepared using a spin-coating method on the PI substrate. Gold was used as electrodes whose gap was 8 ${\mu}m$. These gold electrodes were deposited using a thermal evaporator. Current-voltage (I-V) characteristics of the device were measured using a semiconductor analyzer, HP-4145B. The electrical properties of the device were characterized through hole mobility, $I_{on}/I_{off}$ ratio and threshold voltage. The results showed that the electrical properties of the TFTs on PVP were similar to those of TFTs on $SiO_2$. The bending durability of SiNWs TFTs on PI substrate was also studied with increasing bending times. The results showed that the electrical properties were maintained until the sample was folded about 500 times. But, after more than 1000 bending tests, drain current showed a rapid decrease due to the defects caused by the roughness of the surface of the Si NWs and mismatches of the Si NWs with electrodes.

• 대한치과의사협회지
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• 제48권4호
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• pp.256-262
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• 2010

bone grafting is indicated in the case of bony defects and is classified into autograft, allograft, and xenograft. Synthetic bone graft is contrasted with these three categories in that it has a different donor source. Autograft is most prominent as it is known as a gold standard of all grafting procedures. Its principles and practices are well established via accumulated informations and clinical experiences, which imposes no regulations or restrictions in its clinical use. On the other hand, other bone graft procedures are under tight control for the safety and effectiveness of each product. Food and Drug Administration of the United States has a system in which the information on the approvals and clearances of bone graft materials on their internet homepage. All the bone graft materials that are under the regulations of the United States are classified into the category of medical devices, which includes allogenic bone, xenogenic bone, and synthetic bone graft materials. Each bone graft material has its own indication and the FDA approvals and clearances of medical devices contain the item of "intended use" to specify the indications of each bone graft materials. US dentists, as users of the specific bone graft materials, are provided with adequate information on the approved materials they are to utilize. As an user of these materials, Korean dentists are less provided with the information on the bone graft materials they want to use. Medical providers of the bone graft materials have to be able to provide their users with the essential information such as the intended use of the regulatory approval. Dentists must also be active in gathering informations on the material of their interest, and the system must be built in which both of the medical providers and users of bone graft materials can be satisfied in providing and getting the information, respectively.

• 한국재료학회지
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• 제20권2호
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• pp.51-54
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• 2010

Transparent conductive films of single wall carbon nanotube (SWCNT) were prepared by spray coating method. The effect of acid treatment on the SWCNT films was investigated. The field emission scanning electron microscope (FESEM) shows that acid treatment can remove dispersing agent. The electrical and optical properties of acid-treated films were enhanced compared with those of as deposited SWCNT films. Nitric acid ($HNO_3$), sulfuric acid ($H_2SO_4$), nitric acid:sulfuric acid (3:1) were used for post treatment. Although all solutions reduced sheet resistance of CNT films, nitric acid can improve electrical characteristics efficiently. During acid treatment, transmittance was increased continuously with time. But the sheet resistance was decreased for the first 20 minutes and then increased again. Post-treated SWCNT films were transparent (85%) in the visible range with sheet resistance of about $162{\Omega}/sq$. In this paper we discuss simple fabrication, which is suitable for different types of large-scale substrates and simple processes to improve properties of SWCNT films.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.25.2-25.2
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• 2009

Vertically aligned zinc oxide(ZnO) nanorods (NRs) with different surface morphology were grown by metal organic chemical vapor deposition (MOCVD) on sapphire substrate with different deposition condition. Based on the surface morphology, ZnO nanostructures are divided into three types: nanoneedles, nanonails and nanorods with rounded tip. Variable temperature photoluminescence (PL) have employed to probe the exciton recombination in high density and vertically aligned ZnO Nanorod arrays. Low temperature photoluminescence measurements do not show any significant yellow emission, but the near band edge excitonic emission shows very strong dependence with the surface morphology. The recombination properties are expected to be different due to different surface-to-volume ratio and distribution of potential fluctuations of intrinsic defects.

• 열처리공학회지
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• 제21권2호
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• pp.94-100
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• 2008

The implant prototypes with various porosities were fabricated by Spark Plasma Sintering of atomized spherical titanium balls. The interface was observed by optical microscope. Sintering temperature and holding time were selected at the point of big change of Z-axis ratio during sintering. These experiments show that Spark Plasma Sintering of spherical titanium balls can be efficiently used to produce implants surfaced with titanium balls with various porosities in a short time less than 120 seconds by manipulating the current condition such as z-axis, temperature and balls size.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.240-240
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• 2007

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권2호
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• pp.1519-1521
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• 2007

In this work, a coplanar-type plasma flat fluorescent lamp having cross type of electrode was fabricated by screen printing and sealing technique. Cross type of electrode with a dielectric layer were screen-printed on a rear glass plate, and then fired at $550^{\circ}C$. Phosphor was printed on and fired at $450^{\circ}C$. Finally, the lamp was sealed by frit glass at $450^{\circ}C$. The lamp of cross electrode type was studied depending on the electrode gap and the thickness of dielectric layer.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1313-1316
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• 2005

In the present paper, it was investigated that adhesion layer on gate insulator could affect the electrical characteristics for the organic thin film transistors (OTFTs). The polyimide (PI) as organic adhesion layer was fabricated by using the vapor deposition polymerization (VDP) processing . It was found that electrical characteristics improved comparing OTFTs using adhesion layer to another. We researched adhesion layer as a function of thickness. For inverted-staggered top contact structure, field effect mobility, threshold voltage, and on-off current ratio of OTFTs using adhesion layer of PI 15 nm thickness on the gate insulator with a thickness of 0.2 ${\mu}m$ were about 0.5 $cm^2/Vs$, -0.8 V, and $10^6$, respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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• pp.760-763
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• 2007

The properties of carbon nanotube obtained by thermal chemical vapor deposition (CVD) process were investigated as a function of ammonia $(NH_3)$ gas in hydrocarbon gas, Fe catalyst thickness, and growth temperature. Fe catalyst was prepared by DC magnetron sputter and pre-treated with ammonia gas. CNTs were then grown with ammonia-acetylene gas mixture by thermal CVD. The diameter of these CNTs shows a strong correlation with the gas rate, the catalyst film thickness and temperature. From our results, it was found that the factors of grown CNTs positively acted to improve CNT quality.

• Macromolecular Research
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• 제14권5호
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• pp.524-529
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• 2006

New, thermally robust, arylenevinylene conjugated polymers, including poly(9,9-dioctylfluorenyl-2,7-vinylene) [poly(FV)] and poly[2-(3'-dimethyldodecylsilylphenyl)-1,4-phenylenevinylene] [poly(m-SiPhPV)], were synthesized and used for the fabrication of efficient photovoltaic cells. Bulk heterojunction photovoltaic cells fabricated by blending one of the polymers, [poly(FV)], [poly(m-SiPhPV)], and poly(FV-co-m-SiPhPV), with the fullerene derivative [6,6]-phenyl-$C_{61}$-butyric acid methyl ester (PCBM) were found to have a power conversion efficiency of up to 0.038%..