• Journal of Periodontal and Implant Science
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• v.38 no.sup2
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• pp.373-384
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• 2008

Purpose: The aim of this study is to compare the healing response of various Hydroxyapatite(HA) coated dental implants by Ion-Beam Assisted Deposition(IBAD) placed in the surgically created circumferential gap in dogs. Materials and methods: In four mongrel dogs, all mandibular premolars and the first molar were extracted. After an 8 weeks healing period, six submerged type implants were placed and the circumferential cylindrical 2mm coronal defects around the implants were made surgically with customized step drills. Groups were divided into six groups : anodized surface, anodized surface with 150nm HA and heat treatment, anodized surface with 300nm HA and heat treatment, anodized surface with 150nm HA and no heat treatment, and anodized surface with 150nm HA, heat treatment and bone graft, anodized surface with bone graft. The dogs were sacrificed following 12 weeks healing period. Specimens were analyzed histologically and histomorphometrically. Results: During the healing period, healing was uneventful and implants were well maintained. Anodized surface with HA coating and $430^{\circ}C$ heat treatment showed an improved regenerative characteristics. Most of the gaps were filled with newly regenerated bone. The implant surface was covered with bone layer as base for intensive bone formation and remodeling. In case that graft the alloplastic material to the gaps, most of the coronal gaps were filled with newly formed bone and remaining graft particles. The bone-implant contact and bone density parameters showed similar results with the histological findings. The bone graft group presented the best bone-implant contact value which had statistical significance. Conclusion: Within the scope of this study, nano-scale HA coated dental implants appeared to have significant effect on the development of new bone formation. And additional bone graft is an effective method in overcoming the gaps around the implants.

• Korean Journal of Optics and Photonics
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• v.22 no.1
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• pp.46-52
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• 2011

A confocal microscope was developed utilizing a scanning sample stage based on a home-built double-compound flexure guide. A scanning sample stage with nano-scale resolution consisted of a double leaf spring based flexure, a displacement amplifying lever, a Piezo-electric Transducer(PZT) actuator and capacitance sensors. The performance of the two-axis stage was analyzed using a commercial finite element method program prior to the implementation. A single line laser was employed as the light source along with the Photo Multiplier Tube(PMT) that served as the detector. The performance of the developed confocal microscope was evaluated with a mouse ear skin imaging test. The designed scanning stage enabled us to build the confocal microscope without the two optical scanning mirror modules that are essential in the conventional laser scanning confocal microscope. The elimination of the scanning mirror modules makes the optical design of the confocal microscope simpler and more compact than the conventional system.

• Korean Journal of Metals and Materials
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• v.46 no.11
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• pp.762-769
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• 2008

Hydrogenated amorphous silicon(a-Si : H) layers, 120 nm and 50 nm in thickness, were deposited on 200 $nm-SiO_2$/single-Si substrates by inductively coupled plasma chemical vapor deposition(ICP-CVD). Subsequently, 30 nm-Ni layers were deposited by E-beam evaporation. Finally, 30 nm-Ni/120 nm a-Si : H/200 $nm-SiO_2$/single-Si and 30 nm-Ni/50 nm a-Si:H/200 $nm-SiO_2$/single-Si were prepared. The prepared samples were annealed by rapid thermal annealing(RTA) from $200^{\circ}C$ to $500^{\circ}C$ in $50^{\circ}C$ increments for 30 minute. A four-point tester, high resolution X-ray diffraction(HRXRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and scanning probe microscopy(SPM) were used to examine the sheet resistance, phase transformation, in-plane microstructure, cross-sectional microstructure, and surface roughness, respectively. The nickel silicide on the 120 nm a-Si:H substrate showed high sheet resistance($470{\Omega}/{\Box}$) at T(temperature) < $450^{\circ}C$ and low sheet resistance ($70{\Omega}/{\Box}$) at T > $450^{\circ}C$. The high and low resistive regions contained ${\zeta}-Ni_2Si$ and NiSi, respectively. In case of microstructure showed mixed phase of nickel silicide and a-Si:H on the residual a-Si:H layer at T < $450^{\circ}C$ but no mixed phase and a residual a-Si:H layer at T > $450^{\circ}C$. The surface roughness matched the phase transformation according to the silicidation temperature. The nickel silicide on the 50 nm a-Si:H substrate had high sheet resistance(${\sim}1k{\Omega}/{\Box}$) at T < $400^{\circ}C$ and low sheet resistance ($100{\Omega}/{\Box}$) at T > $400^{\circ}C$. This was attributed to the formation of ${\delta}-Ni_2Si$ at T > $400^{\circ}C$ regardless of the siliciation temperature. An examination of the microstructure showed a region of nickel silicide at T < $400^{\circ}C$ that consisted of a mixed phase of nickel silicide and a-Si:H without a residual a-Si:H layer. The region at T > $400^{\circ}C$ showed crystalline nickel silicide without a mixed phase. The surface roughness remained constant regardless of the silicidation temperature. Our results suggest that a 50 nm a-Si:H nickel silicide layer is advantageous of the active layer of a thin film transistor(TFT) when applying a nano-thick layer with a constant sheet resistance, surface roughness, and ${\delta}-Ni_2Si$ temperatures > $400^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.2
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• pp.409-413
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• 2010

We fabricated 10 nm-thick cobalt silicide($CoSi_2$) as a buffer layer on a p-type Si(100) substrate to investigate the possibility of GaN epitaxial growth on $CoSi_2/Si(100)$ substrates. We deposited 500 nm-GaN on the cobalt silicide buffer layer at low temperature with a PA-MBE (plasma assisted-molecular beam epitaxy) after the $CoSi_2/Si$ substrates were cleaned by HF solution. An optical microscopy, AFM, TEM, and HR-XRD (high resolution X-ray diffractometer) were employed to determine the GaN epitaxy. For the GaN samples without HF cleaning, they showed no GaN epitaxial growth. For the GaN samples with HF cleaning, they showed $4\;{\mu}m$-thick GaN epitaxial growth due to surface etching of the silicide layers. Through XRD $\omega$-scan of GaN <0002> direction, we confirmed the cyrstallinity of GaN epitaxy is $2.7^{\circ}$ which is comparable with that of sapphire substrate. Our result implied that $CoSi_2/Si(100)$ substrate would be a good buffer and substrate for GaN epitaxial growth.

• Journal of radiological science and technology
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• v.33 no.3
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• pp.179-184
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• 2010

A hard X-ray microscope system for obtaining images of nano-spatial resolution has been widely studied and requires monochromatic X-ray. A multilayer mirror of 84% reflectivity was designed to acquire tungsten characteristic X-ray of 8.4 keV from the white beam generated from an X-ray tube, and the C/W multilayer mirror of $50{\times}50\;mm$ size and 5.65 nm d-spacing was fabricated by the ion-beam sputtering system. The C/W multilayer had a uniformity of 99.5%, and the structure of the multilayer mirror was verified by a TEM image. The obtainable x-ray reflectivity for the C/W multilayer mirror at 8.4 keV was estimated from measuring the X-ray reflectivity using the copper characteristic X-ray of 8.05 keV. Monochromatic X-ray of 8.4 keV was generated by combining a X-ray tube, and the reflectivity and monochromaticity were 77.1% and 0.21 keV, respectively. Monochromatic X-ray generated from the combination of an X-ray tube and an C/W multilayer mirror has enough potential to use X-ray source for hard X-ray microscope system of laboratory size. If the C/W multilayer mirror of d-spacing of a few nanometers can be fabricated, monochromatic X-ray corresponded to 17.5 keV, molybdenum characteristic X-ray, can be obtained and applied to mammography in the medical application.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.393-393
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• 2012

Optically active nanostructures such as subwavelength moth-eye antireflective structures or surface enhanced Raman spectroscopy (SERS) active structures have been demonstrated to provide the effective suppression of unwanted reflections as in subwavelength structure (SWS) or effective enhancement of selective signals as in SERS. While various nanopatterning techniques such as photolithography, electron-beam lithography, wafer level nanoimprinting lithography, and interference lithography can be employed to fabricate these nanostructures, roll-to-roll (R2R) nanoimprinting is gaining interests due to its low cost, continuous, and scalable process. R2R nanoimprinting requires a master to produce a stamp that can be wrapped around a quartz roller for repeated nanoimprinting process. Among many possibilities, two different types of mask can be employed to fabricate optically active nanostructures. One is self-assembled Au nanoparticles on Si substrate by depositing Au film with sputtering followed by annealing process. The other is monolayer silica particles dissolved in ethanol spread on the wafer by spin-coating method. The process is optimized by considering the density of Au and silica nano particles, depth and shape of the patterns. The depth of the pattern can be controlled with dry etch process using reactive ion etching (RIE) with the mixture of SF6 and CHF3. The resultant nanostructures are characterized for their reflectance using UV-Vis-NIR spectrophotometer (Agilent technology, Cary 5000) and for surface morphology using scanning electron microscope (SEM, JEOL JSM-7100F). Once optimized, these optically active nanostructures can be used to replicate with roll-to-roll process or soft lithography for various applications including displays, solar cells, and biosensors.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.5
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• pp.206-213
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• 2015

An omni-directional, graded-index and textured ZnO nanorods with $MgF_2$ anti-reflective(AR) coating films for the electro optical tracking system(EOTS) by e-beam evaporation method are presented. we achieved that the graded index structure can minimize image tracking interference of EOTS which is comparable to a general AR coating films. Optimized ZnO nanorods with $MgF_2$ AR coating films lead to decreasing Fresnel reflection by gradient refractive index. According to our experiment results, ZnO nanorods with $MgF_2$ AR coating films can be used for various electro optical system to improve the optical performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4388-4397
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• 2015

The purpose of this study was to research the property change of acrylic resins depending on the induced-beam change and research the improved physical property of dry-heat and microwave-cured dental place acrylic resin in order to develop the acrylic resins with the optimum characteristic. As a result of observing flexural rigidity, hardness and color difference, the dry-heat-cured specimens of Vertex RS and Paladent 20 showed ideal property at 5, 15, and 25 kGy irradiation. The microwave-cured specimens of Vertex RS and Paladent 20 showed ideal property at 5 kGy irradiation. The correlation analysis showed a positive correlation among ARD, flexural rigidity (0 418), E coefficient (0.675) and Barcol hardness (0 588). The radiation cure technology is helpful for relieving the contamination caused by the manufacture of polymer composite. It can significantly contribute to the fusion of ultra violet cure technology and nano technology and the improvement of mechanical property without giving effect to the workability of polymer.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.76.1-76.1
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• 2015

Optical resonances of metallic or dielectric nanoantennas enable to effectively convert free-propagating electromagnetic waves to localized electromagnetic fields and vice versa. Plasmonic resonances of metal nanoantennas extremely modify the local density of optical states beyond the optical diffraction limit and thus facilitate highly-efficient light-emitting, nonlinear signal conversion, photovoltaics, and optical trapping. The leaky-mode resonances, or termed Mie resonances, allow dielectric nanoantennas to have a compact size even less than the wavelength scale. The dielectric nanoantennas exhibiting low optical losses and supporting both electric and magnetic resonances provide an alternative to their metallic counterparts. To extend the utility of metal and dielectric nanoantennas in further applications, e.g. metasurfaces and metamaterials, it is required to understand and engineer their scattering characteristics. At first, we characterize resonant plasmonic antenna radiations of a single-crystalline Ag nanowire over a wide spectral range from visible to near infrared regions. Dark-field optical microscope and direct far-field scanning measurements successfully identify the FP resonances and mode matching conditions of the antenna radiation, and reveal the mutual relation between the SPP dispersion and the far-field antenna radiation. Secondly, we perform a systematical study on resonant scattering properties of high-refractive-index dielectric nanoantennas. In this research, we examined Si nanoblock and electron-beam induced deposition (EBID) carbonaceous nanorod structures. Scattering spectra of the transverse-electric (TE) and transverse-magnetic (TM) leaky-mode resonances are measured by dark-field microscope spectroscopy. The leaky-mode resonances result a large scattering cross section approaching the theoretical single-channel scattering limit, and their wide tuning ranges enable vivid structural color generation over the full visible spectrum range from blue to green, yellow, and red. In particular, the lowest-order TM01 mode overcomes the diffraction limit. The finite-difference time-domain method and modal dispersion model successfully reproduce the experimental results.

• Korean Journal of Materials Research
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• v.20 no.4
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• pp.223-227
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• 2010

Recently, one-dimensional semiconducting nanomaterials have attracted considerable interest for their potential as building blocks for fabricating various nanodevices. Among these semiconducting nanomaterials,, $SnO_2$ nanostructures including nanowires, nanorods, nanobelts, and nanotubes were successfully synthesized and their electrochemical properties were evaluated. Although $SnO_2$ nanowires and nanobelts exhibit fascinating gas sensing characteristics, there are still significant difficulties in using them for device applications. The crucial problem is the alignment of the nanowires. Each nanowire should be attached on each die using arduous e-beam or photolithography, which is quite an undesirable process in terms of mass production in the current semiconductor industry. In this study, a simple process for making sensitive $SnO_2$ nanowire-based gas sensors by using a standard semiconducting fabrication process was studied. The nanowires were aligned in-situ during nanowire synthesis by thermal CVD process and a nanowire network structure between the electrodes was obtained. The $SnO_2$ nanowire network was floated upon the Si substrate by separating an Au catalyst between the electrodes. As the electric current is transported along the networks of the nanowires, not along the surface layer on the substrate, the gas sensitivities could be maximized in this networked and floated structure. By varying the nanowire density and the distance between the electrodes, several types of nanowire network were fabricated. The $NO_2$ gas sensitivity was 30~200 when the $NO_2$ concentration was 5~20ppm. The response time was ca. 30~110 sec.