• Journal of Surface Science and Engineering
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• v.38 no.2
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• pp.73-78
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• 2005

A real-time monitoring of ICP(inductively coupled plasma) assisted magnetron sputtering of MgO was carried out using a QMS(quadrupole mass spectrometer), an OES(optical emission spectrometer), and a digital oscilloscope with a high voltage probe and a current monitor. At the time of ICP ignition, the most distinct impurity was OH emission (308.9 nm) which was dissociated from water molecules. For reactive deposition oxygen was added to Ar and the OH emission intensity was reduced abruptly When the discharge voltage was regulated by a PID controller from 240V(metallic mode) to 120V(oxide mode), the emission intensity from Mg (285.2 nm) changed proportionally to the discharge voltage, but the intensity of Ar I(811.6 nm) was constant. At 100V of discharge voltage, Mg sputtering was almost stopped. Emissions from Ar I(420.1 nm) and Mg I were dropped down to 1/10, but Ar I(811.6 nm) didn't change. And the emission from atomic oxygen (O I, 777.3 nm) was increased to 10 times. These results are compatible with those from QMS study.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.131-133
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• 2012

The photoluminescence (PT) properties of Al-doped ZnO thin films grown by the sol-gel dip-coating method have been investigated. At 12 K, nine distinct PL peaks were observed at 2.037, 2.592, 2.832, 3.027, 3.177, 3.216, 3.260, 3.303, and 3.354 eV. The deep-level emissions (2.037, 2.592, 2.832, and 3.027 eV) were attributed to native defects. The near-band-edge (NBE) emission peaks at 3.354, 3.303, 3.260, 3.216, and 3.177 eV were attributed to the emission of the neutral-donor-bound excitons (D0X), two-electron satellite (TES), free-to-neutral-acceptors (e,A0), donor-acceptor pairs (DAP), and second-order longitudinal optical (2LO) phonon replicas of the TES (TES-2LO), respectively. According to Haynes' empirical rule, we calculated the energy of a free exciton (FX) to be 3.374 eV. The thermal activation energy for D0X in the nanocrystalline ZnO thin film was found to be ~25 meV, corresponding to the thermal dissociation energy required for D0X transitions.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.85-87
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• 2000

In this study, high-density plasma etching characteristics of ITO(indium tin oxide) films used for transparent electrodes in display devices have been investigated. The etch characteristics of ITO as a function of $Ar/CH_4$ gas mixtures were analyzed using QMS(quadrupole mass spectrometry), OES(optical emission spectroscopy), and ESP(electrostatic probe). ITO etch rates were increased with the addition of moderate amount of $CH_4$ to Ar due to the increased chemical reaction between $CH_3$ or H and ITO in addition to the physical sputtering of ITO by Ar ion bombardment. However, the addition of excess amount of $CH_4$ decreased the ITO etch rates possibly due to the increased polymer formation on the ITO surface. Also, the measurement data obtained by QMS and OES suggested that $CH_3$ radicals are more activity involved in the etching of ITO compared to H radicals.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2005.11a
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• pp.37-41
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• 2005

When screen size of the Flat Panel Display (FPD) becomes larger, the traditional photo-lithography using photomasks and UV lamps might not be possible to make patterns on Photo Resist (PR) material due to limitation of the mask size. Though the maskless photo-lithography using UV lasers and scanners had been developed to implement large screen display, it was very slow to apply the process for mass-production systems. The laser exposure system using 405 nm semi-conductor lasers and Digital Micromirror Devices (DMD) has been developed to overcome above-mentioned problems and make more than 100 inches FPD devices. It makes very fine patterns for full HD display and exposes them very fast. The optical engines which contain DMD, Micro Lens Array (MLA) and projection lenses are designed for 10 to 50 ${\mu}m$ bitmap pattern resolutions. The test patterns for LCD and PDP displays are exposed on PR and Dry Film Resists (DFR) which are coated or laminated on some specific substrates and developed. The fabricated edges of the sample patterns are well-defined and the results are satisfied with tight manufacturing requirements.

• Journal of the Korean Magnetics Society
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• v.25 no.6
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• pp.180-184
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• 2015

We have investigated the magnetization reversal behavior in ferromagnetic $Co_{0.5}Fe_{0.5}$ alloy films using the magneto-optical Kerr microscope capable of the direct observation of time-resolved domain patterns. Interestingly enough, as the sample thickness increases the magnetization reversal behavior becomes changed from a single domain wall motion to the random nucleations of domains. Also, from the stochastic analysis of the domain jump sizes during the domain wall motion, it was found that the magnetization reversal behavior in the samples shows the critical scaling behavior with the critical exponent of ${\tau}{\sim}1.33$.

• Korean Journal of Materials Research
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• v.30 no.2
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• pp.99-104
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• 2020

Recent discoveries of ferroelectric properties in ultrathin doped hafnium oxide (HfO₂) have led to the expectation that HfO₂ could overcome the shortcomings of perovskite materials and be applied to electron devices such as Fe-Random access memory (RAM), ferroelectric tunnel junction (FTJ) and negative capacitance field effect transistor (NC-FET) device. As research on hafnium oxide ferroelectrics accelerates, several models to analyze the polarization switching characteristics of hafnium oxide ferroelectrics have been proposed from the domain or energy point of view. However, there is still a lack of in-depth consideration of models that can fully express the polarization switching properties of ferroelectrics. In this paper, a Zr-doped HfO₂ thin film based metal-ferroelectric-metal (MFM) capacitor was implemented and the polarization switching dynamics, along with the ferroelectric characteristics, of the device were analyzed. In addition, a study was conducted to propose an applicable model of HfO₂-based MFM capacitors by applying various ferroelectric switching characteristics models.

• Polymer(Korea)
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• v.28 no.6
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• pp.538-544
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• 2004

Polyurethanes containing L-lysine segments in the main chain (PULL) were synthesized from 4,4'-diphenymethyl diisocynate, poly(tetramethylene glycol), and z-lysine oligomer as a chain extender. Insulin-immobilized polyurethanes (PULL-In) were prepared by a coupling reaction of PULL surface amino groups with insulins. The amount of immobilized insulin was about 0.30 nmol/$\textrm{cm}^2$, as determined by Bradford method. The interactions of NIH/3T3 fibroblasts with surface-modified PULLs were investigated using $^3$H-thymidine incoporation and optical microscopy. The cell growth rate on PULL-In film was higher than those on other substrates. The cell proliferation by the immobilized insulin was almost same as that by the free one.

• Journal of the Semiconductor & Display Technology
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• v.19 no.3
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• pp.88-92
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• 2020

As a highly conductive and transparent electrode, the optical transmittances of ITO/Ag/ITO were simulated and compared with the experimental results. The simulations are based on the finite-difference time-domain (FDTD) method in solving linear Maxwell equations. In our simulations, the computation domain is set in the XZ-plane with 3D dimension, and a plane wave with variable wavelengths ranging from 250 nm to 850 nm is incident in the z-direction at normal incidence to the ITO/Ag/ITO film surrounded by free-air space. As the results through both simulations and experiments, it was shown that the thickness combinations by the ITO layers of about 40 nm and the Ag layer of about 10 nm could be most suitable conditions as a high conductive transparent electrode having the transmittance similar to that of a single ITO layer.

• Korean Journal of Optics and Photonics
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• v.31 no.4
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• pp.176-182
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• 2020

The possibility of replacing the condensing-prism film used in conventional backlight units with a light-guide plate engraved with a submicrometer-periodic diffraction grating was investigated. The optimal period for the diffraction grating was determined through simulation and experiment, and the transmission-mode efficiency of the diffraction grating was calculated in terms of the polar angle and azimuthal angle of the incident light. In addition, the effects of the two methods of optimizing the polar angle and the directional angle were compared by simulation, by suggesting the shape and configuration of the light-guide plate, so that more light could be extracted by diffraction. By using a ray-tracing program, the luminance angular distribution of the light-guide plate engraved with the diffraction grating was calculated and compared to the luminance angular distribution for each actual prototype.

• 연구논문집
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• s.28
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• pp.219-227
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• 1998

In order to investigate the interfacial structure between TiN and iron nitride, an AISI 4140 steel was nitrided to form a layer of thickness 15$\mum$ by DC ion nitriding, then the surface was bombarded with Ti ions and subsequently coated a TiN film of 5$\mum$ by arc ion plating method. The interfacial microstructure between TiN and iron nitride was characterized by optical microscope, SEM and XRD. So called black layer was observed in the duplex treatment. It was resulted from the decomposition of iron nitride during the bombardment. Its thickness was increased with increasing bombardment time at high bias voltage. But the thickness was greatly decreased when the iron nitride was bombarded with a nitrogen gas or at a reduced bias voltage. The adhesion strength of the top TiN coating was decreased with increasing thickness of the black layer. Furthermore, the reduced adhesion strength in this system was discussed in view of the interfacial structural relationship between TiN and iron nitride.