• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.297-297
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• 2008

Buffer layers play an important role in the development of high critical current density coated conductor. $LaMnO_3$, $SrTiO_3$ and $BaZrO_3$ buffer layers were compatible with MgO surfaces and also provide a good template for growing high current density REBCO(RE=Rare earth) films. Systematic studies on the influences of pulsed laser deposition parameters (deposition temperature, deposition pressure, processing gas, laser energy density, etc.) on microstructure and texture properties of $LaMnO_3$, $SrTiO_3$ and $BaZrO_3$ films as buffer layer deposited on ion-beam assisted deposition MgO (IBAD_MgO) template by pulse laser deposition method, were carried out. These results will be presented together with the discussion on the possible use of this material in HTS coated conductor as buffer.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.5
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• pp.659-674
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• 2000

A large increase in the use of thin film coating of hydroxyapatite(HA) in implant dentistry is driven by the desire to take advantage of the excellent biocompatibility and high strength of HA coating. The purpose of this study was to evaluate the effects of HA-coated implants by ion Beam Assisted Deposition(IBAD) method in comparison to the sand-blasted and machined surfaces. Osteoblast culture test, removal torque test and histomorphometric analysis were performed and the following results obtained; 1. Examination of the osteoblast cultures displayed no difference in the secretion of alkaline phosphatase between the various specimen, but IBAD with pure HA specimen showed low alkaline phosphatase secretion(p<0.05). 2. Removal torque tests showed HA-coated implants by IBAD method to be similar in high value to the implants with sand-blasted surface than the implants with machined surface. And the ovariectomized group showed low mechanical test value than the normal group(p<0.05). 3. Histomorphometrical comparisons were performed on undecalcified ground sections. HA-coated implants by IBAD method demonstrated the highest mean bone-to-metal contact ratio on all threads and 3-best consecutive threads, and the implants with sand-blasted surface and implants with machined surface was in the next consecutive order(p<0.05). HA-coated implants showed slightly higher bone-to- metal contact ratio than sand-blasted implants, but no statistically significant difference was obtained between the two materials. The ovariectomized group showed lower value of bone-to-metal contact ratio than the normal group, but no statistically significant difference was obtained between the two groups. 4. Evaluation of bone volume on all threads and 3-best consecutive threads showed no statistically significant difference among the different surface treatment groups, but showed lower bone volume in ovariectomized group than in the normal group(p<0.05). According tn these results, thin film coated implants with HA showed high bone contact ratio, bone volume and removal torque strength in the short term, but long term observation is needed.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.1
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• pp.131-143
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• 2007

Statement of the problem: In case of poor bone quality or immediately loaded implant, various strategies have been developed focusing on the surface of materials to improve direct implant fixation to the bone. The microscopic properties of implant surfaces play a major role in the osseous healing of dental implant. Purpose of study: This study was undertaken to evaluate bone response of ion beam-assisted deposition(IBAD) of hydroxyapatite(HA) on the anodized surface of subperiosteal titanium implants. Material and methods: Two half doughnut shape subperiosteal titanium implants were made. The control group was treated with Anodized surface treatment and the test group was treated with IBAD of HA on control surface. Then two implants inserted together into the subperiosteum of the skull of 30 rats and histological response around implant was observed under LM(light microscope) and TEM(transmission electron microscope) on 4th, 6th and 8th week. Results: Many subperiosteal implants were fixed with fibrous connective tissue not with bony tissue because of weak primary stability. The control group observed poor bone response and there was no significant change at any observation time. However the test group showed advanced bone formation and showed direct bone to implant contact under LM on 8th week. The test group observed much rER in the cell of osteoblast but the control group showed little rER under TEM. Conclusions: The test group showed better bone formation than the control group at the condition of weak primary stability. With these results IBAD surface treatment method on Anodized surface, may be good effect at the condition of weak primary stability.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.3
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• pp.362-374
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• 2007

Statement of problem. The intial stability for osseointegration of implant has been an interesting factor. Especially, in the case of poor bone quality or immediately loaded implant, various strategies have been developed focusing on the surface of materials to improve implant fixation to bone. The microscopic properties of implant surfaces play a major role in the osseous healing of dental implants. Purpose. The aims of this study are to perform a histologic and histomorphometric comparison of the healing characteristics of three different surfaces and the comparison of resonance frequency analysis (RFA) values measured by $Osstell^{TM}$ and perio-test values (PTV) measured by Periotest. Material and methods. A total of 24 screw titanium implants (Dentium Co., Seoul, Korea) with 6mm in length and 3.4mm in diameter, were placed in the mandible of 4 beagle dogs. Implants were divided into three groups following the surface treatment methods: Group I is machined(control group). Group II is anodically oxidized. Group III is coated 500nm in thickness with hydroxyapatite(HA) by ion beam assisted deposition(IBAD) on the anodized oxidization. Bone blocks from 2 dogs were caught after 3 weeks of covered healing and another blocks from 2 dogs after 6 weeks. RFA values and PTV were measured right after insertion and at 3 and 6weeks. Histomorphometric analysis was made with Kappa Image Base System to calculate bone-to-implant contact (BIC) and bone area inside the threads. Pearson's correlation analyses were performed to evaluate the correlation between RFA and PTV, BIC and bone area ratio of three different surfaces at 3 and 6 weeks. Results. 1) In all surface treatment methods, the RFA values decreased and the PTV values increased until 6 weeks in comparison to initial values. 2) At 3 weeks, no significant difference was found from bone-to-implant contact ratio and bone area ratio of three different surface treatment methods(P>0.05). However, at 6 weeks, different surface treatment methods showed significantly different bone-toimplant contact ratio and bone area ratio(P<0.05). 3) In the implants with the IBAD on the anodic oxidization, significant difference was found between the 3 weeks and the 6 weeks bone area ratio(P<0.05). 4) Correlation was found between the RFA values and the bone area ratio at 3 and 6 weeks with significant difference(P<0.05). Conclusions. These results indicate that the implants with the IBAD on the anodic oxidization may have a high influence on the initial stability of implant.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1276-1279
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• 2005

The long-term stability of pentacene thin-film transistors (TFTs) encapsulated with a transparent $SnO_2$ thin-film prepared by ion beam assisted deposition (IBAD) was investigated. With a buffer layer of thermally evaporated 100 nm $SnO_2$ film deposited prior to IBAD process, our encapsulated OTFTs sustained its initial field-effect mobility up to one month and then gradually degraded showing only 37% reduction compared to 90% reduction of non-encapsulated OTFTs after 100 days in air ambient. The encapsulated OTFTs also exhibited superior on/off current ratio of over $10^5$ to that of the unprotected devices $({\sim}10^4)$ which was reduced from ${\sim}10^6$ before aging. Therefore, the enhanced long-term stability of our encapsulated OTFTs should be attributed to well protection of permeation of $H_2O$ and $O_2$ into the devices by the IBAD $SnO_2$ thin-film which could be used as an effective inorganic gas barrier for transparent organic electronic devices.

• Journal of Surface Science and Engineering
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• v.29 no.6
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• pp.788-796
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• 1996

$TiO_2$ films prepared by RF magnetron sputtering, electron beam evaporation, ion assisted deposition (IAD) and sol-gel method are prepared on c-Si substrate and vitreous silica substrate respectively. From the transmission spectra of $TiO_2$ films on vitreous silica substrate in the spectral region from 190 nm to 900 nm, k($\lambda$) of $TiO_2$ is obtained. Using k($\lambda$) in the interband transition region the coefficients of the quantum mechanical dispersion relation of an amorphous $TiO_2$ and hence n($\lambda$) including the optically opaque region of above fundamental transition energy are obtained. The spectroscopic ellipsometry spectra of $TiO_2$ films in the spectral region of 1.5-5.0eV are model analyzed to get the film packing density variation versus i) substrate material, ii) film thickness and iii) film growth technique. The complex refractive index change of these $TiO_2$ films versus water condensation is also studied. Film micro-structures by SE modelling results are compared with those by atomic force microscopy images and X-ray diffraction data.

• Tribology and Lubricants
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• v.18 no.1
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• pp.1-8
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• 2002

Nano adhesion and friction between a $Si_{3}N_{4}$ AFM(atomic force microscope) tip and thin silver films were experimentally studied. Tests were performed to measure the nano adhesion and friction in both AFM and LFM(lateral force microscope) modes in various range of normal loads. Thin silver films deposited by IBAD (ion beam assisted deposition) on Si-wafer (100) and other Si-wafers of different surface roughness were used. Results showed that nano adhesion and friction decreased with the surface roughness. When the Si surfaces were coated by pure silver, the adhesion and friction decreased. But the adhesion and friction were not affected by the thickness of IBAD silver coating. As the normal force increased, the adhesion forces of bare Si-wafer and IBAD silver coating film remained constant, but the friction forces increased linearly. Test results suggested that the friction was mainly governed by the adhesion as long as the load was low.

• Korean Journal of Materials Research
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• v.5 no.3
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• pp.297-309
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• 1995

본 연구에서는 이온선보조증착법에 의해 Si(100)기판위에 정합성장된 $Si_{0.5}$Ge_{0.5}$층의 핵성성과 성장을 고찰하였다. 성장층에 대한 AFM(Atomic Force Microscopy), RHEED(Reflection High Energy Electron diffraction) 등의 분석결과 Si(100)기판위에 이온선보조증착에 의하여 성장된 $Si_{0.5}$Ge_{0.5}$층은 Stranski-Kranstanov(SK)기구로 성장되며, 300eV, 10 $\mu$A/$cm^{2}$의 Ar이온선을 조사시키는 경우 결정성이 향상되었고, SK 성장 방식의 임계두께가 증가하였다. Ar 이온선 조사에 의해 MBE에 의한 정합성장온도(55$0^{\circ}C$-$600^{\circ}C$)보다 훨씬 낮은 20$0^{\circ}C$에서 정합성장이 가능하였으며, $x_{mn}$값은 10.5%로 MBE에 의한 정합성장시 보고된 $x_{mn}$ 값보다 낮았다. 이온충돌에 의해 발생한 3차원 island의 분해와 표면확산의 증가가 $Si_{0.5}$Ge_{0.5}$층의 성장에 현저한 영향을 미쳤으며, 이온충돌의 영향은 3차원 island의 생성보다 3차원 island의 분해가 더 안정한 낮은 증착온도에서만 관찰되었다.

• Transactions on Electrical and Electronic Materials
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• v.11 no.2
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• pp.49-53
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• 2010

Microstructural origins of leakage current and physical degradation during operation in product-quality AlGaN/GaN high electron mobility transistor (HEMT) devices were investigated using photon emission microscopy (PEM) and transmission electron microscopy (TEM). AlGaN/GaN HEMTs were fabricated with metal organic chemical vapor deposition on semi-insulating SiC substrates. Photon emission irregularity, which is indicative of gate leakage current, was measured by PEM. Site specific TEM analysis assisted by a focused ion beam revealed the presence of threading dislocations in the channel below the gate at the position showing strong photon emissions. Observation of electrically degraded devices after life tests revealed crack/pit shaped defects next to the drain in the top AlGaN layer. The morphology of the defects was three-dimensionally investigated via electron tomography.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.12
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• pp.814-818
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• 2016

DSSCs (dye-sensitized solar cells) based on $TiO_2/SiO_2$ multi layer AR (anti-reflection) coating on the outer glass FTO (fluorine-doped tin oxide) substrate are investigated. We have coated an AR layer on the surface of a DSSCs device by using an IAD (ion beam-assisted deposition) system and investigated the effects of the AR layer by measuring photovoltaic performance. Compared to the pure FTO substrate, the multi layer AR coating increased the total transmittance from 67.4 to 72.9% at 530 nm of wavelength. The main enhancement of solar conversion efficiency is attributed to the reduction of light reflection at the FTO substrate surface. This leads to the increase of Jsc and the efficiency improvement of DSSCs.