• The Journal of Advanced Prosthodontics
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• v.6 no.2
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• pp.96-102
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• 2014

PURPOSE. This study was performed to characterize the effects of zirconia coated with calcium phosphate and hydroxyapatite compared to smooth zirconia after bone marrow-derived osteoblast culture. MATERIALS AND METHODS. Bone marrow-derived osteoblasts were cultured on (1) smooth zirconia, (2) zirconia coated with calcium phosphate (CaP), and (3) zirconia coated with hydroxyapatite (HA). The tetrazolium-based colorimetric assay (MTT test) was used for cell proliferation evaluation. Scanning electron microscopy (SEM) and alkaline phosphatase (ALP) activity was measured to evaluate the cellular morphology and differentiation rate. X-ray photoelectron spectroscopy (XPS) was employed for the analysis of surface chemistry. The genetic expression of the osteoblasts and dissolution behavior of the coatings were observed. Assessment of the significance level of the differences between the groups was done with analysis of variance (ANOVA). RESULTS. From the MTT assay, no significant difference between smooth and surface coated zirconia was found (P>.05). From the SEM image, cells on all three groups of discs were sporadically triangular or spread out in shape with formation of filopodia. From the ALP activity assay, the optical density of osteoblasts on smooth zirconia discs was higher than that on surface treated zirconia discs (P>.05). Most of the genes related to cell adhesion showed similar expression level between smooth and surface treated zirconia. The dissolution rate was higher with CaP than HA coating. CONCLUSION. The attachment and growth behavior of bone-marrow-derived osteoblasts cultured on smooth surface coated zirconia showed comparable results. However, the HA coating showed more time-dependent stability compared to the CaP coating.

• Applied Chemistry for Engineering
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• v.17 no.6
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• pp.586-590
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• 2006

As one of electro active polymers for soft smart materials, the ionic polymer metal composites (IPMC) are easy to produce through chemical reduction processing and show high displacements at low voltage. When the IPMC actuates, the deformation depends on a few factors including the structure of based membrane, species and morphology of the metal electrodes, the nature of cations and the level of hydration. As previously published, we have been studying on improvement of actuation through surface electrode modification of IPMC to grasp the effect of electrode morphology on actuation. This study is comparative experiments through the chemical reaction and deposition by ion beam assisted deposition (IBAD) in order to prepare the very thin and homogeneous surface electrode of IPMC. The IPMCs were prepared with different surface roughness of polymer membrane, and the influence of the surface roughness on the actuation was studied. By investigating the electrical properties and driving displacement, the actuating properties of IPMC with different surface roughness were studied.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.2
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• pp.45-49
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• 1999

A flammable gas sensor based on the $SnO_2$thin film deposited by the reactive ion assisted deposition was fabricated and ultra-thin Pd layer as catalyst was adsorbed at surface by ion beam sputtering. The initial oxidation states of Pd catalyst were controlled to investigate the role of Pd in the sensing process of inflammale gas sensor through annealing in air and vacuum respectively. The Pd catalyst existing in pure metallic state showed the sensitivity higher than that of PdO. The result might be closely related to the fact that PdO as a surface acceptor would receive electrons via Pd sub-channel from $SnO_2$, and thus which reduces the sensitivity and delay the response time.

• Journal of the Korean Vacuum Society
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• v.9 no.2
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• pp.155-161
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• 2000

BN films composed of c-BN(70%) and h-BN(30%) phases have been synthesized by the ion beam assisted deposition (IBAD) process and stabilized by post-annealing. Boron was e-beam evaporated at 1.2 $\AA$/sec and nitrogen was ionized and accelerated at about 100 eV by the end-hall type ion gun. Substrates were negatively biased by DC 400 and 500 V, respectively, and heated at $700^{\circ}C$. Synthesized BN films were in-situ post-annealed at 700 or $800^{\circ}C$, respectively, for 1 hr without breaking vacuum. BN films without post-annealing were peeled off from substrates immediately when they were exposed to the air while those with post-annealing at $800^{\circ}C$ were stabilized. Post annealing reduced the film stress from 4.9 GPa to 3.4 GPa, but no considerable stress release in the c-BN phase was observed, contrary to previous reports that the stress relaxation in the c-BN phase is the main mechanism for the stabilization. Structural and chemical relaxation of non c-BN phase is supposed to be responsible for the film stress reduction and, in turn, stabilization, especially when the c-Bn content of the film is not high.

• The Journal of Engineering Research
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• v.3 no.1
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• pp.189-197
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• 1998

Hyeroxyapatite(HAp) which has good biocompatibility was made by Wet Chemical Process. The surface of Ti-6Al-4V, coated with HAp by lon Beam Assisted Deposition (IBAD), was treated with 5ppm, 10ppm, 20ppm, and 100ppm of $AgNO_3$ solution. In this Ag impregnation process, $Ca^{2+}$ of HAp was substituted with $Ag^+$ of $AgNO_3$. In this study, the antimicrobial effect and biocompatibility of Ti-6Al-4V alloy which was coated with Ag-HAp were examined. The antimicrobial test was carried out with two kinds of bacteria(P. Aeruginosa, S. Epidermidis), which are highly infectious in a transplanting operation of implant materials. As a result of the test, it was observed that Ti-6Al-4V alloy which was treated by 20ppm of $AgNO_3$ solution has good biocompatibility. In order to observe the antimicrobial mechanism of $Ag^+$, E. coli which is the most common bacterium was treated by Ag-HAp. Then cell morphology of E. coli was observed by the transmission electron microscope(TEM). The destruction of cell wall and cytoplasm of E. coil were observed. A black spot appeared in the cytoplasm was analyzed by energy dispersive analysis X-ray (EDAX) and it showed a small amount of $Ag^+$. Thus, it was proved that $Ag^+$ destroys bacteria effectively and Ti-6Al-4V alloy which was impregnate with Ag ion show antimicrobial effect on infection bacteria.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.157-157
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• 2015

Recently, the growing interest in organic microelectronic devices including OLEDs has led to an increasing amount of research into their many potential applications in the area of flexible electronic devices based on plastic substrates. However, these organic devices require a gas barrier coating to prevent the permeation of water and oxygen because organic materials are highly susceptible to water and oxygen. In particular, high efficiency OLEDs require an extremely low water vapor transition rate (WVTR) of $1{\times}10^{-6}g/m^2day$. The Key factor in high quality inorganic gas barrier formation for achieving the very low WVTR required ($1{\times}10^{-6}g/m^2day$) is the suppression of defect sites and gas diffusion pathways between grain boundaries. In this study NBAS process was introduced to deposit enhanced film density single gas barrier layer with a low WVTR. Fig. 1. shows a schematic illustration of the NBAS apparatus. The NBAS process was used for the $Al_2O_3$ nano-crystal structure films deposition, as shown in Fig. 1. The NBAS system is based on the conventional RF magnetron sputtering and it has the electron cyclotron resonance (ECR) plasma source and metal reflector. $Ar^+$ ion in the ECR plasma can be accelerated into the plasma sheath between the plasma and metal reflector, which are then neutralized mainly by Auger neutralization. The neutral beam energy is controlled by the metal reflector bias. The controllable neutral beam energy can continuously change crystalline structures from an amorphous phase to nanocrystal phase of various grain sizes. The $Al_2O_3$ films can be high film density by controllable Auger neutral beam energy. we developed $Al_2O_3$ high dense barrier layer using NBAS process. We can verified that NBAS process effect can lead to formation of high density nano-crystal structure barrier layer. As a result, Fig. 2. shows that the NBAS processed $Al_2O_3$ high dense barrier layer shows excellent WVTR property as a under $2{\times}10^{-5}g/m^2day$ in the single barrier layer of 100nm thickness. Therefore, the NBAS processed $Al_2O_3$ high dense barrier layer is very suitable in the high efficiency OLED application.

• Progress in Superconductivity
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• v.6 no.1
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• pp.69-73
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• 2004

Ni alloy tape is electropolished to be used as a metal substrate for fabrication of IBAD (ion-Beam Assisted Deposition)-MgO texture template fur HTS coated conductor. Electropolishing is needed to obtain a very smooth surface of Ni alloy tape because the in-plane texture of templates is sensitive to the roughness of metal substrate. The critical current of YBCO coated conductor depends on the texture of YBCO that depends on the texture of the IBAD MgO layer. And so the smoothness of the metal substrate is directly related to the superconducting properties of the coated conductor. In this study, we have prepared a reel-to-reel electropolishing apparatus to polish the Ni alloy tapes for IBAD. Various electropolishing conditions were investigated to improve the surface roughness. Hastelloy tape is continuously electropolished with high polishing current density (0.5 ∼ 2 A/$\textrm{cm}^2$) and fast processing time (1 ∼ 3 min). Polished hastelloy tapes have surface roughness(RMS) of below 1 nm on a 5 ${\times}$ 5 $\mu\m^2$ from AFM and SEM.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.1
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• pp.78-94
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• 2005

Purpose. The purpose of this study was to compare the effects of various surface treatments by measuring resonance frequency and histomorphometric analyses. Material and methods. In 5 adult dogs, the mandibular premolar were extracted. Six months later, 30 screw titanium implants (Dentium Co., Seoul, Korea) 6mm in length and 3.4mm in diameter, were placed in the mandibles of 5 dogs. Implants were divided into five groups following to surface treatment methods ; Group 1 is machined controls, Group 2 is sandblasted with large grit and acid-etched (SLA), Group 3 is anodized (Autoelectric Co., Korea, 660Hz, Duty10), Group 4 is hydroxyapatite(HA) coated by ion beam assisted deposition(E-beam), Group 5 is hydroxyapatite(HA) coated with Sol-gel coating process. Resonance frequency was measured implant placement immediately, and 3, 6 weeks and 10 weeks of healing perods. With the animal subject's sacrifice 10 weeks after implantation, implants were removed on bloc and histologic and computer-based histomorphometric analyses were performed. Histomorphometric analysis involved quantification of the entire bone to metal contact around the implants. Statistical analyses were performed using the SPSS for Windows (ver. 9.0 SPSS Inc.) Statistical differences were considered significant at P<0.05. Results. The results were as follows : 1) In five groups, mean value of resonance frequency analysis(RFA) were highest in group 5 (Sol-gel implant) at implantation and those of group 4 (E-beam)was highest at 10 weeks . but there was no correlation between surface treatments and RFA. 2) In all surface treatment groups, the RFA values of implants decreased until 3 weeks and increased to 10 weeks. 3) The percentage of direct bone-to-implant contact (BIC) had statistical significance between five groups in cancellous bone, (P<0.05) the percentage of bone density inside the thread had no statistical significance between five groups. (P>0.05) 4) There was a significant difference between cortical bone and cancellous bone in BIC. (P<0.05) and bone density. (P<0.05) 5) There was a correlation between the RFA value of implants at 10 weeks and BIC in cancellous bone, and between the RFA value of implants at 10 weeks and bone density in cortical bone. (P<0.05). Conclusions. These results indicate that surface treatment does not affect the implant stability in case of good bone quality.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.100-101
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• 2012

The plasma damage free and room temperature processedthin film deposition technology is essential for realization of various next generation organic microelectronic devices such as flexible AMOLED display, flexible OLED lighting, and organic photovoltaic cells because characteristics of fragile organic materials in the plasma process and low glass transition temperatures (Tg) of polymer substrate. In case of directly deposition of metal oxide thin films (including transparent conductive oxide (TCO) and amorphous oxide semiconductor (AOS)) on the organic layers, plasma damages against to the organic materials is fatal. This damage is believed to be originated mainly from high energy energetic particles during the sputtering process such as negative oxygen ions, reflected neutrals by reflection of plasma background gas at the target surface, sputtered atoms, bulk plasma ions, and secondary electrons. To solve this problem, we developed the NBAS (Neutral Beam Assisted Sputtering) process as a plasma damage free and room temperature processed sputtering technology. As a result, electro-optical properties of NBAS processed ITO thin film showed resistivity of $4.0{\times}10^{-4}{\Omega}{\cdot}m$ and high transmittance (>90% at 550 nm) with nano- crystalline structure at room temperature process. Furthermore, in the experiment result of directly deposition of TCO top anode on the inverted structure OLED cell, it is verified that NBAS TCO deposition process does not damages to the underlying organic layers. In case of deposition of transparent conductive oxide (TCO) thin film on the plastic polymer substrate, the room temperature processed sputtering coating of high quality TCO thin film is required. During the sputtering process with higher density plasma, the energetic particles contribute self supplying of activation & crystallization energy without any additional heating and post-annealing and forminga high quality TCO thin film. However, negative oxygen ions which generated from sputteringtarget surface by electron attachment are accelerated to high energy by induced cathode self-bias. Thus the high energy negative oxygen ions can lead to critical physical bombardment damages to forming oxide thin film and this effect does not recover in room temperature process without post thermal annealing. To salve the inherent limitation of plasma sputtering, we have been developed the Magnetic Field Shielded Sputtering (MFSS) process as the high quality oxide thin film deposition process at room temperature. The MFSS process is effectively eliminate or suppress the negative oxygen ions bombardment damage by the plasma limiter which composed permanent magnet array. As a result, electro-optical properties of MFSS processed ITO thin film (resistivity $3.9{\times}10^{-4}{\Omega}{\cdot}cm$, transmittance 95% at 550 nm) have approachedthose of a high temperature DC magnetron sputtering (DMS) ITO thin film were. Also, AOS (a-IGZO) TFTs fabricated by MFSS process without higher temperature post annealing showed very comparable electrical performance with those by DMS process with $400^{\circ}C$ post annealing. They are important to note that the bombardment of a negative oxygen ion which is accelerated by dc self-bias during rf sputtering could degrade the electrical performance of ITO electrodes and a-IGZO TFTs. Finally, we found that reduction of damage from the high energy negative oxygen ions bombardment drives improvement of crystalline structure in the ITO thin film and suppression of the sub-gab states in a-IGZO semiconductor thin film. For realization of organic flexible electronic devices based on plastic substrates, gas barrier coatings are required to prevent the permeation of water and oxygen because organic materials are highly susceptible to water and oxygen. In particular, high efficiency flexible AMOLEDs needs an extremely low water vapor transition rate (WVTR) of $1{\times}10^{-6}gm^{-2}day^{-1}$. The key factor in high quality inorganic gas barrier formation for achieving the very low WVTR required (under ${\sim}10^{-6}gm^{-2}day^{-1}$) is the suppression of nano-sized defect sites and gas diffusion pathways among the grain boundaries. For formation of high quality single inorganic gas barrier layer, we developed high density nano-structured Al2O3 single gas barrier layer usinga NBAS process. The NBAS process can continuously change crystalline structures from an amorphous phase to a nano- crystalline phase with various grain sizes in a single inorganic thin film. As a result, the water vapor transmission rates (WVTR) of the NBAS processed $Al_2O_3$ gas barrier film have improved order of magnitude compared with that of conventional $Al_2O_3$ layers made by the RF magnetron sputteringprocess under the same sputtering conditions; the WVTR of the NBAS processed $Al_2O_3$ gas barrier film was about $5{\times}10^{-6}g/m^2/day$ by just single layer.

• The Journal of Engineering Research
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• v.3 no.1
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• pp.181-187
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• 1998

Hydroxyapatite was used as implant materials, because it has a good biocompatibility and is similar to human bone. However it is not expected to have a high strength as implant materials because of a low fracture strength after sintering of HAp. Alumina ($\alpha$-alumina) shows a stable chemical properties and high strength in physiological environments. Thus it was tried to use a HAp coatings on Alumina substrate as implant materials. In this study, HAp was coated on Alumina substrate by lon Beam Assisted Deposition(IBAD). Then Ag was impregnated on HAp coating layer, which showed antimicrobial effects. To carry out the ion exchange of $Ag^+$ with $Ca^{2+}$ in HAp on the surface, HAp coated alumina substrate was immersed in 20ppm, 100ppm $AgNO_3$ solution at room temperature for 48 hours. Antimicrobial test was studied by using bacteria, which normally caused periprosthetic infections. The follwing bacteria was used in antimicrobial test. Escherichia coli, Pseudomonas aeruginosa (gram negative) and staphylococcus epidermidis (gram positive). Ag impregnated HAp shows very good antimicrobial effects against these bacteria. The surface structure of sample, which was treated in $AgNO_3$ solution was studied by SEM, XRD. Ag release curve was studied in Simulated Body Fluid (SBF) solution.