• Journal of the Korean Society for Heat Treatment
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• v.24 no.2
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• pp.87-91
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• 2011

Single layer Sn doped $In_2O_3$ (ITO) films and ITO 50 nm / Au 10 nm / ITO 40 nm (IAI) multilayer films were prepared with electron beam assisted magnetron sputtering on glass substrates. The effects of the Au interlayer, post-deposition atmosphere annealing and intense electron irradiation on the methanol gas sensitivity were investigated at room temperature. As deposited ITO films did not show any diffraction peaks in the XRD pattern, while the IAI films showed the diffraction peak for $In_2O_3$ (400). In this study, the gas sensitivity of ITO and IAI films increased proportionally with the methanol vapor concentration and an intense electron beam irradiated IAI film shows the higher sensitivity than the others film. From the XRD pattern, it is supposed that increased crystallization promotes the gas sensitivity. This approach is promising in gaining improvement in the performance of IAI gas sensors used for the detection of methanol vapor at room temperature.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.538-539
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• 2013

여러 장점으로 인해 OLED는 디스플레이 및 조명 등 적용분야가 넓어지고 있지만, 수분 및 산소에 취약하여 그 수명이 제한되는 단점이 있다. 이를 해결하고자 현재까지는 glass cap을 이용한 encapsulation 기술이 적용되고 있지만, flexible 기판에 적용하지 못하는 문제가 있다. 이러한 문제를 해결하고자 여러 가지 thin film encapsulation 기술이 적용되고 있으나 보다 신뢰성이 높은 기술의 개발이 절실한 때이다. Encapsulation 무기 박막 물질로서 $Si_3N_4$ 박막은 PE-CVD (Plasma Enhanced Chemical Vapor Deposition) 등의 박막 증착법을 사용한 많은 연구가 진행되어, 저온에서의 좋은 품질의 박막 증착이 가능하지만, 100도 이하의 thermal budget을 갖는 OLED Encapsulation에 사용하기에는 충분하지 않았다. CVD 박막의 특성을 더욱 개선하기 위해 최근 ALD (Atomic Layer Deposition) 방법을 통한 $Al_2O_3$ film 증착 방법이 연구되고 있지만, 낮은 증착 속도로 인해 양산에 걸림돌이 되고 있다. 본 연구에서는 또 다른 해결책으로서 Digital CVD 방법을 이용한 양질의 $Si_3N_4$ 박막의 증착을 연구하였다. 이것은 ALD 증착법과 유사하며, 1st step에서 PECVD 방법으로 4~5 ${\AA}$의 얇은 silicon 박막을 증착하고, 2nd step에서 nitrogen plasma를 이용하여 질화 반응을 진행하고, 이러한 cycle을 원하는 두께가 될 때까지 반복적으로 진행된다. 이 때 1 cycle 당 증착속도는 7 ${\AA}$/cycle 정도였다. 최적의 증착 방법과 조건으로 기존의 CVD $Si_3N_4$ 박막 대비 1/5 이하로 pinhole을 최소화 할 수는 있지만 완벽하게 제거하기는 힘든 문제가 있고, 이를 해결하기 위한 개선을 위한 접근 방법이 필요하다고 판단하였다. 본 연구에서는 무기물 박막인 carbon nitride를 이용한 SiN/C:N multilayer 증착 연구를 진행하였다. Fig. 1은 CVD 조건으로 증착된 두께 750 nm SiN film에서 여러 층의 C:N film layer를 삽입했을 때, 38 시간의 85%/$85^{\circ}C$ 가속실험에 따라 OLED의 발광 사진이다. 그림에서 볼 수 있듯이 C:N 층을 삽입하고 또한 그 박막의 수가 증가함에 따라서 OLED에 대한 encapsulation 특성이 크게 개선됨을 확인할 수 있다.

• Journal of the Korean Magnetics Society
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• v.23 no.4
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• pp.122-125
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• 2013

Perpendicular magnetic anisotropy (PMA) is the phenomenon of magnetic thin film which is preferentially magnetized in a direction perpendicular to the film's plane. Amorphous multilayer with PMA has been studied as the good candidate to realization of high density STT-MRAM (Spin Transfer Torque-Magnetic Random Access Memory). The current issue of high density STT-MRAM is a decrease in the switching current of the device and an application of amorphous materials which are most suitable devices. The amorphous ferromagnetic material has low saturated magnetization, low coercivity and high thermal stability. In this study, we presented amorphous ferromagnetic multilayer that consists of an amorphous alloy CoSiB and a nonmagnetic material Pd. We investigated the change of PMA of the $[CoSiB\;t_{CoSiB}/Pd\;1.3nm]_5$ multilayer ($t_{CoSiB}$ = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 nm, and $t_{Pd}$ = 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6 nm) and $[CoSiB\;0.3nm/Pd\;1.3nm]_n$ multilayer (n = 3, 5, 7, 9, 11, 13). This multilayer is measured by VSM (Vibrating Sample Magnetometer) and analyzed magnetic properties like a coercivity ($H_c$) and a magnetization ($M_s$). The coercivity in the $[CoSiB\;t_{CoSiB}\;nm/Pd\;1.3nm]_5$ multi-layers increased with increasing $t_{CoSiB}$ to reach a maximum at $t_{CoSiB}$ = 0.3 nm and then decreased for $t_{CoSiB}$ > 0.3 nm. The lowest saturated magnetization of $0.26emu/cm^3$ was obtained in the $[CoSiB\;0.3nm/Pd\;1.3nm]_3$ multilayer whereas the highest coercivity of 0.26 kOe was obtained in the $[CoSiB\;0.3nm/Pd\;1.3nm]_5$ mutilayer. Additional Pd layers did not contribute to the perpendicular magnetic anisotropy. The single domain structure evolved in to a striped multi-domain structure as the bilayer repetition number n was increased above 7 after which (n > 7) the hysteresis loops had a bow-tie shapes.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.4
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• pp.357-362
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• 2011

Purpose: The narrow-band pass color-filters with a 500 nm central wavelength and 12 nm FWHM using $Ti_3O_5/SiO_2$ mutilayer were fabricated, and their characteristics and structures were studied. Methods: the optical constants, n and k, of the $Ti_3O_5$ and $SiO_2$ thin films were obtained from the transmittances of their thin film. The narrow-band pass color-filters were designed with these optical constants and the AR coating of the filter was also designed. $Ti_3O_5/SiO_2$ multilayer filters were made by electron beam evaporation apparatus and the transmittaces of the filters were measured by spectrophotometer. the number of layers and the thicknesses of filters were calculated from the cross section of filters by SEM image and the composition of filters was analysed by XPS analysis. Results: The optimization of AR coating for the narrow-band pass color-filter was [air$|SiO_2(90)|Ti_3O_5(36)|SiO_2(5)|Ti_3O_5(73)|SiO_2(30)|Ti_3O_5(15)|$ glass], and the optimization of filter layer for the color filter was [air$|SiO_2(192)|Ti_3O_5(64)|SiO_2(102)|Ti_3O_5(66)|SiO_2(112)|Ti_3O_5(74)|SiO_2(120)|Ti_3O_5(68)|SiO_2(123)|Ti_3O_5(80)|SiO_2(109)|Ti_3O_5(70)|SiO_2(105)|Ti_3O_5(62)|SiO_2(99)|Ti_3O_5(63)|SiO_2(98)|Ti_3O_5(51)|SiO_2(60)|Ti_3O_5(42)|SiO_2(113)|Ti_3O_5(88)|SiO_2(116)|Ti_3O_5(68)|SiO_2(89)|Ti_3O_5(49)|SiO_2(77)|Ti_3O_5(48)|SiO_2(84)|Ti_3O_5(51)|SiO_2(85)|Ti_3O_5(48)|SiO_2(59)|Ti_3O_5(34)|SiO_2(71)|Ti_3O_5(44)|SiO_2(65)|Ti_3O_5(45)|SiO_2(81)|Ti_3O_5(52)|SiO_2(88)|$ glass]. It was known that the color-filters fabricated by the simulation data were composed of 41 layers by SEM image and the top layer of filters was $SiO_2$ layer and the filters were composed of $SiO_2$/$Ti_3O_5$ multilayer by XPS analysis. It was also known that the mixed thin film of TiO2 and $Ti_3O_5$ was made during the deposition of the $Ti_3O_5$ material. Conclusions: The narrow-band pass color-filters with a 500 nm central wavelength and 12 nm FWHM using $Ti_3O_5/SiO_2$ mutilayer of 41 layer were fabricated, and it was known that the mixed form of TiO2 and $Ti_3O_5$ thin film was made during the deposition of the $Ti_3O_5$ material.

• Applied Chemistry for Engineering
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• v.25 no.1
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• pp.41-46
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• 2014

The property improvement of polycarbonate coated with a multilayer film composed of an inorganic $SiO_2$ film and a photocatalytic $TiO_2$ film was studied. The $SiO_2$ film as a binder had an excellent light transmission characteristic. After the treatment with atmospheric pressure plasma, the surface of $SiO_2$ film showed the hydrophilicity, which increased the film coating uniformity with a $TiO_2$-containing aqueous solution. When $TiO_2$ film was over 200 nm thick, the absorption effect of UV rays in the range of 180~400 nm suppressed the yellowing phenomena of polycarbonate substrate. The inorganic film improved the heat resistance of polycarbonate substrates. $TiO_2$ film in the outmost under the exposure of UV rays promotes the catalytic oxidation characteristics and yields the capability to the decomposition of organic contaminants, and also increases the self-cleaning properties due to the increase of hydrophilicity. Structural stability of the polycarbonate substrate coated with inorganic $TiO_2$ and $SiO_2$ film was shown. The role of $SiO_2$ film between $TiO_2$ and polycarbonate substrate suppressed the peeling of $TiO_2$ film by inhibiting the photocatalytic oxidation effect of $TiO_2$ film on the polycarbonate substrate.

• Journal of the Korean Vacuum Society
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• v.15 no.1
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• pp.110-116
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• 2006

The mechanical property and cutting performance of the cutting tools coated with nanoscale nyktukatered nitride film have been investigated. $Ti_{0.54}Al_{0.46}N-CrN$ and $Ti_{0.84}Al_{0.16}N-NlN$ systems, which showed super-lattice in nanoscale multilayered coating, were deposited on WC-Co insert by UBM sputtering, The superlattice coatings with different bilayer periods were manufactured by controlling deposition parameters. The superlattice formation and hardness of the nanoscale multilayered nitride film and the cutting performance of the insert coated with the film were examined. The hardness and cutting performance were dependent on the bilayer periods of the coatings. The flank wear of the inserts with superlattice coatings were decreased over $20\%$, compared to those of commonly used cutting tools coated with TiAIN single phase.

• Journal of the Korean Magnetics Society
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• v.20 no.3
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• pp.89-93
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• 2010

We study the giant magneto-resistance (GMR), coercivity and their dependence on the ferromagnetic layers adjacent to the nonmagnetic layer in a spin-valve structure, [Pd/ferromagnetic] multilayers with perpendicular anisotropy. We fabricated a basic spinvalve structure of $[Pd/Co]_2$/ferro-magnetic layer/nonmagnet/ferro-magnetic layer/$[Pd/Co]_2$/FeMn and investigated the dependence of its GMR and magnetic properties such ad coercivity on the ferromagnetic material to reduce the coercivity of the free layer. We try to reduce the freelayer coercivity by controlled the anisotropy, we insert the material NiFe, $Co_8Fe_2$, $Co_9Fe_1$ to ferromagnetic layers adjacent to the Cu layer. Then, we have been able to reduce the coercivity as low as 100 Oe, and also achieved 6.7% of magneto-resistance ratio when the ferromagnetic layer thickness was 0,7 nm.

• Journal of the Korean Magnetics Society
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• v.20 no.2
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• pp.35-40
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• 2010

The GMR-SV (giant magnetoresistance-spin valve) device depending on the micro patterned features according to two easy directions of longitudinal and transversal axes has been studied. The GMR-SV multilayer structure was Ta(5 nm)/NiFe(8 nm)/Cu(2.3 nm)/NiFe(4 nm)/IrMn(8 nm)/Ta(2.5 nm). The applied anisotropy direction of the GMR-SV thin film was performed under the magnitude of 300 Oe using by permanent magnet during the deposition. The size of micro patterned device was a $1\;{\times}\;18\;{\mu}m^2$ after the photo lithography process. In the aspects of the shape magnetic anisotropy effect, there are two conditions of fabrication for GMR-SV device. Firstly, the direction of sensing current was perpendicular to the magnetic easy axis of the pinned NiFe/IrMn bilayer with the transversal direction of device. Secondly, the direction of shape magnetic anisotropy was same to the magnetic easy axis of the free NiFe layer with the longitudinal direction of device.

• Macromolecular Research
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• v.10 no.1
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• pp.2-12
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• 2002

The small-angle X-ray scattering (SAXS) beamline BL4C1 at the 2.5 GeV storage ring of the Pohang Accelerator Laboratory (PAL) has been in its first you of operation since August 2000. During this first stage it could meet the basic requirements of the rapidly growing domestic SAXS user community, which has been carrying out measurements mainly on various polymer systems. The X-ray source is a bending magnet which produces white radiation with a critical energy of 5.5 keV. A synthetic double multilayer monochromator selects quasi-monochromatic radiation with a bandwidth of ca. 1.5%. This relatively low degree of monochromatization is sufficient for most SAXS measurements and allows a considerably higher flux at the sample as compared to monochromators using single crystals. Higher harmonics from the monochromator are rejected by reflection from a flat mirror, and a slit system is installed for collimation. A charge-coupled device (CCD) system, two one-dimensional photodiode arrays (PDA) and imaging plates (IP) are available its detectors. The overall performance of the beamline optics and of the detector systems has been checked using various standard samples. While the CCD and PDA detectors are well-suited for diffraction measurements, they give unsatisfactory data from weakly scattering samples, due to their high intrinsic noise. By using the IP system smooth scattering curves could be obtained in a wide dynamic range. In the second stage, stating from August 2001, the beamline will be upgraded with additional slits, focusing optics and gas-filled proportional detectors.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.173-173
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• 2010

$Bi_4Ti_3O_{12}$ ($B_4T_3$) is a unique ferroelectric material that has a relatively high dielectric constant, high Curie temperature, high breakdown strength, and large spontaneous polarization. As a result this material has been widely studied for many applications, including nonvolatile ferroelectric random memories, microelectronic mechanical systems, and nonlinear-optical devices. Several reports have appeared on the use of Mn dopants to improve the electrical properties of $B_4T_3$ thin films. Mn ions have frequently been used for this purpose in thin films and multilayer capacitors in situations where intrinsic oxygen vacancies are the major defects. However, no systematic study of the optical properties of $B_4T_3$ films has appeared to date. Here, we report optical data for these films, determined by spectroscopic ellipsometry (SE). We also report the effects of thermal annealing and Mn doping on the optical properties. The SE data were analyzed using a multilayer model that is consistent with the original sample structure, specifically surface roughness/$B_4T_3$ film/Pt/Ti/$SiO_2$/c-Si). The data are well described by the Tauc-Lorentz dispersion function, which can therefore be used to model the optical properties of these materials. Parameters for reconstructing the dielectric functions of these films are also reported. The SE data show that thermal annealing crystallizes $B_4T_3$ films, as confirmed by the appearance of $B_4T_3$ peaks in X-ray diffraction patterns. The bandgap of $B_4T_3$ red-shifts with increasing Mn concentration. We interpret this as evidence of the existence deep levels generated by the Mn transition-metal d states. These results will be useful in a number of contexts, including more detailed studies of the optical properties of these materials for engineering high-speed devices.