• Korean Journal of Optics and Photonics
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• v.31 no.6
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• pp.321-327
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• 2020

We investigated the light reflection from thin films coated on substrates. Using a prism with a high refractive index as the incident medium, the phenomena of the total internal reflection (TIR) of the prism/film/substrate system and the light coupling into the optical waveguide formed by the air/film/substrate system were comprehensively studied and compared. If the refractive index of the thin film is greater than that of the substrate, within the TIR region of the substrate, sharp reflection minima occur at specific angles where the waveguide modes are excited, that can be used to accurately measure the refractive index and thickness of a thin film. On the other hand, if the refractive index of the thin film is smaller than that of the substrate, such waveguide modes do not exist. In this case, although not so distinct as a bulk medium, the TIR effect of the thin film is still observable, accompanied by an interference pattern. In this study we analyzed the overall reflection phenomena occurring from prism/film/substrate structures, to investigate the possibility of measuring the refractive index of a thin film in both cases.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.5
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• pp.344-349
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• 2015

A new information society of late has arrived by the rapid development of various information & communications technologies. Accordingly, mobile devices which are light and thin, easy and convenient to carry on the market. Also, the requirements for the larger television sets such as fast response speed, low-cost electric power, wider visual angle display are sufficiently satisfied. The currently most widely studied display material, the Organic Light-emitting Diodes(OLEDs) overwhelms the Liquid Crystal Display(LCD), the main occupier of the market. This new material features a response speed of more than a thousand times faster, no need of backlight, a low driving voltage, and no limit of view angle. And the OLEDs has high luminance efficiency and excellent durability and environment resistance, quite different from the inorganic LED light source. The OLEDs with simple device structure and easy produce can be manufactured in various shapes such as a point light source, a linear light source, a surface light source. This will surely dominate the market for the next generation lighting and display device. The new display utilizes not the glass substrate but the plastic one, resulting in the thin and flexible substrate that can be curved and flattened out as needed. In this paper, OLEDs device was produced by changing thickness of Teflon-AF of hole injection material layer. And as for the electrical properties, the four layer device of ITO/TPD/$Alq_3$/BCP/LiF/Al and the five layer device of ITO/Teflon AF/TPD/$Alq_3$/BCP/Lif/Al were studied experimentally.

• Journal of the Korean Ceramic Society
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• v.41 no.10 s.269
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• pp.766-770
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• 2004

High-transmittance film was coated by using spherical silica nano colloids. Silica colloid sol was preservred between two inclined slide glasses by capillary force, and particles were stacked to form a film onto the substrate as the upper glass was sliding. As the sliding speed increased, the thickness of the film decreased and light transmittance varied. The microstructure observed by SEM showed that silica particles were nearly close packed, which enabled the calculation of the effective refractive index of the film. The film thickness calculated from the wavelength of maximum transmittance and the effective refractive index was well coincided with the thickness observed by SEM and measured by profiler. The maximum transmittance of $94.7\%$ was obtained. This means that $97.4\%$ of transmittance or $1.3\%$ of reflectance can be achieved by simple process if both sides of the substrate are coated.

• Journal of Surface Science and Engineering
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• v.42 no.1
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• pp.21-25
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• 2009

Using an evaporation system, $SiO_2$ was deposited as a buffer layer between a PET substrate and a ITO layer and then ITO/$SiO_2$/PET layers were annealed for 1.5 hours at the temperature of $180^{\circ}C$. Adhesion and electro-optical properties of ITO films were studied with thickness variance of a $SiO_2$ buffer layer. As a result of introduction of the $SiO_2$ buffer layer, sheet resistance and resistivity increased and a ITO film with optimum sheet resistance ($529.3{\Omega}/square$) for an upper ITO film of resistive type touch panel could be obtained when $SiO_2$ of $50{\AA}$ was deposited. And it was found that ITO films with $SiO_2$ buffer layer have higher transmittance of $88{\sim}90%$ at 550 nm wavelength than ITO films with no buffer layers and the transmittance was enhanced as $SiO_2$ thickness increased from $50{\AA}$ to $100{\AA}$. Adhesion property of ITO films with $SiO_2$ buffer layers became better than ITO films with no buffer layers and this property was independent of $SiO_2$ thickness variance ($50{\sim}100{\AA}$). By depositing a $SiO_2$ buffer layer of $50{\AA}$ on the PET substrate and sputtering a ITO thin film on the layer, a ITO film with enhanced adhesion, electro-optical properties could be obtained.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.4
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• pp.463-470
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• 2016

In this paper, the characteristics analysis of LMD track, such as including track structure, track wear resistance and track thickness, were analyzed to enhance the deposition efficiency using a diode-pumped disk laser. SKD61 hot work steel plate and Fe based AISI M2 alloy were used as a the substrate and powder for the LMD process, respectively. The laser power, track pitch and powder feed rate among LMD parameters were adopted to estimate the deposition efficiency. As the laser power is increased, heat input and melting pool on the substrate is grown also increases, so resulting in the increased LMD track thickness was increased. Through EPMA mapping analysis of the cross-section in the LMD track, it was observed that all the elements are evenly distributed inside. Therefore, the entire hardness in the LMD track is expected to be almost uniform regardless of location. The characteristics of the LMD specimen were excellent compared to the STD11 specimen in terms of the wear track width and the wear rate as well as the coefficient of friction. Especially the wear rate of LMD specimen has been significantly reduced by 60 % or more. From Based on the experimental results, the prediction formula of LMD thickness was calculated by using laser power, track pitch and powder feed rate.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.700-702
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• 2005

A 5.0-inch transmissive type plastic TFT arrays were successfully fabricated on a plastic substrate at the resolution of $400{\times}3{\times}300$ lines (100ppi). All of the TFT processes were carried out below $150^{\circ}C$ on PES plastic films. After thin film deposition using PECVD, thin film failures such as film delamination and cracking often occurred. For successful growth of thin films (about 1um) without their failures, it is necessary to solve the critical problem related to the internal compressive stress (some GPa) leading to delamination at a threshold thickness value of the films. The Griffith's theory explains the failure process by looking at the excess of elastic energy inside the film, which overcomes the cohesive energy between film and substrate. To increase the above mentioned threshold thickness value there are two possibilities: (i) the improvement of the interface adhesion (for example, through surface micro-roughening and/or surface activation), and (ii) the reduction of the internal stress. In this work, reducing a-Si layer film thickness and optimizing a barrier SiNx layer have produced stable CVD films at 150oC, over PES substrates

• Korean Journal of Materials Research
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• v.20 no.1
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• pp.47-50
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• 2010

Various thicknesses of Al-doped ZnO (AZO) films were deposited on glass substrate using pulsed dc magnetron sputtering with a cylindrical target designed for large-area high-speed deposition. The structural, electrical, and optical properties of the films of various thicknesses were characterized. All deposited AZO films have (0002) preferred orientation with the c-axis perpendicular to the substrate. Crystal quality and surface morphology of the films changed according to the film thickness. The samples with higher surface roughness exhibited lower Hall mobility. Analysis of the measured data of the optical band gap and the carrier concentration revealed that there were no changes for all the film thicknesses. The optical transmittances were more than 85% regardless of film thickness within the visible wavelength region. The lowest resistivity, $4.13\times10^{-4}\Omega{\cdot}cm^{-1}$ was found in 750 nm films with an electron mobility $(\mu)$ of $10.6 cm^2V^{-1} s^{-1}$ and a carrier concentration (n) of $1.42\times10^{21} cm^{-3}$.

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.650-656
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• 1995

High frequency SAW filters for cellular communications were fabricated by metallizing 36$^{\circ}$Y-X LiTaO$_3$piezoelectric substrate with IIDT type electrodes. It was found that the center frequency of the filter was lowered than as designed. In order to overcome such a drawback and enable a fine tuning of its center frequency, dielectric SiN$_{x}$ thin films were deposited on LiTaO$_3$substrate by PECVD as passivation layer and then frequency responses were also characterized. As a result, the center frequency of the filter could be shifted to a higher frequency with increasing the thickness of SiN$_{x}$ film, because SAW velocity increased with increasing the ratio of the thickness of dielectric thin film to wavelength. The insertion loss of the filter, however, became larger with increasing the thickness of SiN$_{x}$ film.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.356-356
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• 2010

Tribological behaviors of the hard film on soft substrate system were explored using the hard thin film of diamond-like carbon (DLC) coated the soft polymer of polydimethysiloxane (PDMS). A DLC film with the Young's modulus of 100 GPa was coated on PDMS substrate with Young's modulus of 10 MPa using plasma enhanced chemical vapor deposition (PECVD) technique. The deposition time was varied from 10 sec to 10 min, resulting in nanoscale roughness of wrinkle patterns with the thickness of 20 nm to 510 nm, respectively, at a bias voltage of $400\;V_b$, working pressure 10 mTorr. Nanoscale wrinkle patterns with 20-100 nm in width and 10-30 nm height were formed on DLC coating due to the residual stress in compression and difference in Young's modulus. Nanoscale roughness effect on tribological behaviors was observed by performing a tribo-experiment using the ball-on-disk type tribometer with a steel ball of 6 mm in diameter at the sliding speed of 220 rpm, normal load of 1N and 25% humidity at ambient temperature of $25^{\circ}C$. Friction force were measured with respect to thickness change of coated DLC thin film on PDMS. It was found that with increases the thickness of DLC coating on PDMS, the coefficient of friction decreased by comparison to that of the uncoated PDMS. The wear tracks before and after tribo-test were analyzed using SEM and AFM.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.196.1-196.1
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• 2016

TCO(Transparent Conducting Oxide) on flat glass is used in thin-film photovoltaic cell, flat-panel display. Nowadays, Corning(R) Willow Glass(R), known as flexible substrate, has attracted much attention due to its many advantages such as reliable roll-to-roll glass processing, high-quality flexible electronic devices, high temperature process. Also, it can be an alternative to flexible polymer substrates which have their poor stability and degradation of electrical and optical qualities. For application on willow glass, the flexibility, electrical, optical properties can be greatly influenced by the TCO thin film thickness due to the inherent characterization of thin film in nanoscale. It can be expected that while thick TCO layer causes poor transparency, its sheet resistance become low. Also, rarely reports were focusing on the influence of flexible properties by varying TCO thickness on flexible glass. Therefore, it is very important to optimize TCO thickness on flexible Willow glass. In this study, Ti-ZnO thin films, with different thickness varied from 0 nm to 50 nm, were deposited on the flexible willow glass by atomic layer deposition (ALD). The flexible, electrical and optical properties were investigated, respectively. Also, these properties of Ti-doped ZnO thin films were compared with un-doped ZnO thin film. Based on the results, when Ti-ZnO thin films thickness increased, resistivity decreased and then saturated; transmittance decreased. The Figure of Merit (FoM) and flexibility was the highest when Ti-ZnO thickness was 40nm. The flexible, electrical and optical properties of Ti-ZnO thin films were better than ZnO thin film at the same thickness.