• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.241-241
• /
• 2007

We fabricated SmBCO coated conductors(CCs) on IBAD-MgO templates using co-evaporation method. IBAD-MgO templates consist of PLD-LMO/epi-MgO/IBAD-MgO/Ni-alloy and showed good in-plane texture of below FWHM 7 degree. Evaporation rates of Sm, Ba, and Cu were precisely controlled to get the optimum composition ratio after deposition process. To optimize the oxygen partial pressure of reaction region, wide range of the partial pressure was investigated from 1 mTorr to 15 mTorr. By reducing the oxygen partial pressure to 5mTorr, (103)grains in SmBCO layer have been increased. On the other hand, there were only (001)grains in SmBCO layer deposited at 15 mTorr $O_2$. Deposition temperature was also investigated from $600^{\circ}C\;to\;800^{\circ}C$ to make high Ic SmBCO CCs. SmBCO on IBAD MgO template showed that the Ic increased gradually at higher growth temperature to $800^{\circ}C$, which the highest Jc and Ic is $2.6\;MA/cm^2$ and 500 A/cm-w., respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.429-429
• /
• 2007

For various applications of liquid crystal displays (LCDs), the uniform alignment of liquid crystal (LC) molecules on treated surfaces is significantly important. Generally, a rubbing method has been widely used to align the LC molecules on polyimide (PI) surfaces. Rubbed PI surfaces have suitable characteristics, such as uniform alignment. However, the rubbing method has some drawbacks, such as the generation of electrostatic charges and the creation of contaminating particles. Thus, we strongly recommend a non contact alignment technique for future generations of large high-resolution LCDs. Most recently, the LC aligning capabilities achieved by ultraviolet and ion-beam exposures which are non contact methods, on diamond-like carbon (DLC) inorganic thin film layers have been successfully studied because DLC thin films have a high mechanical hardness, a high electrical resistivity, optical transparency, and chemical inertness. In addition, nitrogen-doped DLC (NDLC) thin films exhibit properties similar to those of the DLC thin films and a higher thermal stability than the DLC thin films because C:N bonding in the NDLC thin filmsis stronger against thermal stress than C:H bonding in the DLC thin films. Our research group has already studied the NDLC thin films by an ion-beam alignment method. The $SiN_x$ thin films deposited by plasma-enhanced chemical vapor deposition are widely used as an insulation layer for a thin film transistor, which has characteristics similar to those of DLC inorganic thin films. Therefore, in this paper, we report on LC alignment effects and pretilt angle generation on a $SiN_x$, thin film treated by ion-beam irradiation for various N ratios

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.08a
• /
• pp.84-91
• /
• 2002

The stochiometric composition of $AgGaS_2$/GaAs polycrystal source materials for the $AgGaS_2$/GaAs epilayer was prepared from horizontal furnace. From the extrapolation method of X-ray diffraction patterns it was found that the polycrystal $AgGaS_2$/GaAs has tetragonal structure of which lattice constant an and Co were 5.756 $\AA$ and 10.305 $\AA$, respectively. $AgGaS_2$/GaAs epilayer was deposited on throughly etched GaAs(100) substrate from mixed crystal $AgGaS_2$/GaAs by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $590^{\circ}C$ and $440^{\circ}C$ respectively. The crystallinity of the grown $AgGaS_2$/GaAs epilayer was investigated by the DCRC (double crystal X-ray diffraction rocking curve). The optical energy gaps were found to be 2.61 eV for $AgGaS_2$/GaAs epilayer at room temperature. The temperature dependence of the photocurrent peak energy is well explained by the Varshni equation, then the constants in the Varshni equation are given by $\alpha=8.695{\times}10^{-4}$ eV/K, and $\beta=332K$. From the photocurrent spectra by illumination of polarized light of the $AgGaS_2$/GaAs epilayer, we have found that crystal field splitting ${\Delta}Cr$ was 0.28 eV at 20 K. From the PL spectra at 20 K, the peaks corresponding to free and bound excitons and a broad emission band due to D-A pairs are identified. The binding energy of the free excitons are determined to be 0.2676 eV and 0.2430 eV and the dissociation energy of the bound excitons to be 0.4695 eV.

• Journal of the Korean Magnetics Society
• /
• v.8 no.6
• /
• pp.380-387
• /
• 1998

In this paper, a sensor material with Fe/Zr multilayer thin film, in which the change in the magnetization and strain with hydrogenation is maximized, were developed. Compositionally modulated (CM) Fe/Zr multilayers with a $Fe_{80}Zr_{20}$ composition and modulation wavelengths ($\lambda$) $3~50{\AA}$ were deposited by sequentially sputtering (RF diode) elemental Fe and Zr targets. The films were electrolytically hydrogenated to select the optimum Fe/Zr multilayers that show the maximum increases in the magnetization and strain with hydrogenation. The changes in the magnetic properties of the thin films after hydrogenation, were measured using a hysteresis graph and a vibrating sample magnetometer (VSM), and the strains induced in the films by hydrogenation were also measured using a laser heterodyne interferometer (LHI). The optimum sensor material selected was incorporated in a fiber-optic hydrogen sensor (that can sense indirectly amount of hydrogen injected) by depositing it directly on the sensing arm of a single-mode fiber Michelson interferometer. The developed sensor holds significant promise for non-destructive test evaluation (NDE) applications because it is expected to be useful for detecting easily and accurately the subsurface corrosion in structural systems.

• Journal of The Geomorphological Association of Korea
• /
• v.23 no.1
• /
• pp.17-33
• /
• 2016

Samples from newly exposed outcrop of sedimentary layers forming Jeongdongjin coastal terrace in Gangreung area are collected and analyzed to find the sedimentary environment. The site are located at the gentle hillslope of the terrace surface area. The height of the outcrop is about 8m and the altitude of it's highest part is 68~73m MSL. The lowest part of this out crop is the partly consolidated sand layer with gravel veneer within it. It is found that this part is not in-situ weathered sand stone through the OSL method. This sand layer is overlain by the gravel layer with sand matrix. The shapes of the gravels from this part are mainly 'platy', 'elongated', and 'bladed' by the index of Sneed and Folk(1958). In addition, mean roundness is not so high. It is sceptical to regard this part as marine sediments which are continuously exposed to erosional processes. The boundary between the lowest sand layer and gravel layer showing the abrupt change in forming material without any mixture or transitional zone, so gravels are seemed to deposited after some degree of consolidation of the lowest sand layer. In addition, the hight of the boundary between layers are changed by the place, so the surface of the partly consolidated sand layer is not flat and has irregularity on topography when it buried by gravels. Main part of this out crop is the poorly sorted coarse gravel(22.4mm) with sand matrix($1.36{\phi}$) layer with at least 2m thick covering the relatively fine gravels discussed above. Over 20% of particles have 'very platy', 'very elongated' and 'very bladed' shape and only less than 5% of particles have 'compact' shape, So this particles are also very hard to be regard as marine gravels which are abraded by marine processes. It can be concluded that this gravel layer formed by fluvial processes rather than coastal processes base on the form of the clast and sedimentary structure. The gravel layer is covered by fine($3{\sim}4{\phi}$) material layers of psudo-gleization which showing inter-bedding of red and white layers. Chemical composition of matrix and other fine materials should be analyzed in further studies. It is attempted to fine the burial ages of the sediment using OSL method, but failed by the saturation. So it can be assumed that these sediments have be buried over 120ka.

• Korean Journal of Metals and Materials
• /
• v.48 no.5
• /
• pp.456-461
• /
• 2010

We investigated the In-based ohmic contacts on Nitrogen-face (N-face) n-type GaN, as well as Ga-face n-type GaN, for InGaN-based vertical Light Emitting Diodes (LEDs). For this purpose, we fabricated Circular Transfer Length Method (CTLM) patterns on the N-face n-GaN that were prepared by using a laser-lift off method, as well as on the Ga-face n-GaN that were prepared by using a dry etching method. Then, In/transparent conducting oxide (TCO) and In/TiW schemes were deposited on the CTLM in order for low resistance ohmic contacts to form. The In/TCO scheme on the Ga-face n-GaN showed high specific contact resistance, while the minimum specific contact resistance was only 3${\times}$10$^{-2}$ $\Omega$-cm$^{2}$ after annealing at 300${^{\circ}C}$, which can be attributed to the high sheet resistance of the TCO layer. In contrast, the In/TiW scheme on the Ga-face n-GaN produced low specific contact resistance of 2.1${\times}$10$^{5}$ $\Omega$-cm$^{2}$ after annealing at 500${^{\circ}C}$ for 1 min. In addition, the In/TiW scheme on the N-face n-GaN also resulted in a low specific contact resistance of 2.2${\times}$10$^{-4}$ $\Omega$-cm$^{2}$ after annealing at 300${^{\circ}C}$. These results suggest that both the Ga-face n-GaN and N-face n-GaN.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.35 no.1
• /
• pp.44-49
• /
• 2022

In this paper, we investigated current (I)- and voltage (V)-sweeping properties in a double-stack structure, Ge₂Sb₂Te₅/Ti/W-doped Ge₈Sb₂Te₁₁, a candidate medium for applications to multilevel phase-change memory. 200-nm-thick and W-doped Ge₂Sb₂Te₅ and W-doped Ge₈Sb₂Te₁₁ films were deposited on p-type Si(100) substrate using magnetron sputtering system, and the sheet resistance was measured using 4 point-probe method. The sheet resistance of amorphous-phase W-doped Ge₈Sb₂Te₁₁ film was about 1 order larger than that of Ge₂Sb₂Te₅ film. The I- and V-sweeping properties were measured using sourcemeter, pulse generator, and digital multimeter. The speed of amorphous-to-multilevel crystallization was evaluated from a graph of resistance vs. pulse duration (t) at a fixed applied voltage (12 V). All the double-stack cells exhibited a two-step phase change process with the multilevel memory states of high-middle-low resistance (HR-MR-LR). In particular, the stable MR state is required to guarantee the reliability of the multilevel phase-change memory. For the Ge₂Sb₂Te₅ (150 nm)/Ti (20 nm)/W-Ge₈Sb₂Te₁₁ (50 nm), the phase transformations of HR→MR and MR→LR were observed at t<30ns and t<65ns, respectively. We believe that a high speed and stable multilevel phase-change memory can be optimized by the double-stack structure of proper Ge-Sb-Te films separated by a barrier metal (Ti).

• Journal of the Korean Society of Radiology
• /
• v.3 no.2
• /
• pp.27-31
• /
• 2009

Now a days, the Medical X-ray equipments has become digitalized from analog type such as film, cassette to CR, DR. And many scientists are still researching and developing the Medical X-ray equipment. In this study, we used the Bismuth tri-iodide to conversion material for digital X-ray equipments and we couldn't get the satisfying result than previous study, but it opened new possibility to cover the disadvantage of a-Se is high voltage aplly and difficultness of make. In this paper, we use $BiI_3$ powder(99.99%) as x-ray conversion material and make films that have thickness of 200um and the film size is $3cm{\times}3cm$. Also, we deposited an ITO(Indium Tin Oxide) electrode as top electrode and bottom electrode using a Magnetron Sputtering System. To evaluate a characteristics of the produced films, an electrical and structural properties are performed. Through a SEM analysis, we confirmed a surface and component part. And to analyze the electrical properties, darkcurrent, sensitivity and SNR(Signal to Noise Ratio) are measured. Darkcurrent is $1.6nA/cm^2$ and sensitivity is $0.629nC/cm^2$ and this study shows that the electrical properties of x-ray conversion material that made by screen printing method are similar to PVD method or better than that. This results suggest that $BiI_3$ is suitable for a replacement of a-Se because of the reduced manufacture processing and improved yield.

• The Korean Journal of Petroleum Geology
• /
• v.5 no.1_2 s.6
• /
• pp.48-58
• /
• 1997

Core samples from the B, E, F, H wells in the Tertiary Pohang Basin were analysed for total organic carbon (TOC) content and subject to Rock-Eval pyrolysis in order to assess petroleum geochemical characteristics of organic matter. Following geochemical screening, we selected samples from each well for the study of bitumen and kerogens such as optical observation, infra-red spectroscopy and biomarker analyses. Sediments of the Tertiary Yonil Group contain total organic carbon ranging from $0.55{\%} to 3.74{\%}$ with S1+S2 values higher than 2mgHC/g Rock in B, E and F wells, which indicates fair hydrocarbon generation potential. Most organic matter in the B, E, F wells is compared to type II based on the Rock-Eval pyrolysis, infra-red spectroscopy and optical observation. However, organic matter in the H well is compared to type III because the well is located at the margin of the basin where the preservation of terrestrial material is dominant. Geochemical analyses show that organic matter in the Yonil Group is thermally immature although thermal maturity slightly increases with depth. Maturity levels of the extracted kerogens are similar to those of bulk samples ($Tmax<435^{\circ}C$. Petroleum geochemical charateristics of the sediments in the Tertairy Yonil Group is fair in terms of the organic richness and hydrocarbon genetic potential, but organic matter is thermally immature due to the shallow burial depth. Optical observation of the kerogens and biomarker analysis show that organic matter in the Yonil Group is both marine and terrestrial origin, although it was deposited in marine environment. Pristane/phytane ratio suggests rather anoxic depositional environment. Transitional characteristics of organic matter indicate that the marine Yonil Group was deposited near the terrestrial environments. Input of terrestrial organic matter is more prevalent in the samples recovered from the lowermost horizon in the wells due to the terrestrial environment at the time of basin formation.

• Journal of Korean Ophthalmic Optics Society
• /
• v.19 no.2
• /
• pp.179-188
• /
• 2014

Purpose: The present study was aimed to investigate the cleaning efficacy of multi-purpose solutions containing different types and content of surfactants and their effect on the visible light transmittance of soft lens. Methods: Soft lenses made of different materials (etafilcon A and hilafilcon B) were deposited tear proteins by using the artificial tear and then compared the resulting cleaning efficacy and visible light transmittance after cleaning the lens with 6 types of multi-purpose solutions containing different content of surfactants. Results: The cleaning efficacy of multi-purpose solutions was variously shown as approximately 23~43% according to the active concentration of surfactants and surface tension in multi-purpose solution when etafilcon A lens cleaned with rubbing. The highest cleaning efficacy was detected when cleaned with the multi-purpose solution containing hydrogen peroxide besides surfactant however, the amount of remaining protein was still high on the lens. After washed with multi-purpose solution, the visible light transmittance of lens was in 89.8 to 90.8%. The amount of protein deposited on hilafilcon B lens was very small compared with it on etafilcon A lens even though it was incubated in artificial tears for 7 days, which showed 5~10% of protein amount in etafilcon A lens and the decrease of visible light transmittance was also not significant. In case of rubbing with multi-purpose solution, the cleaning efficacy on hilafilcon B lens was in 45.4 to 67.4% however, the order of cleaning efficacy of multi-purpose solution was different from it on etafilcon A lens. The visible light transmittance of hilafilcon B lens has been restored to the level of new lens. Conclusions: From the result, it is concluded that the appropriate multi-purpose solution should be selected according to the lens material and the amount of protein deposit on the basis of understanding surfactants and active principle for proper care of protein deposit on soft lens and the cleaning with rubbing is more efficient for lens care regardless of manufacturer's guideline.