• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.11
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• pp.961-968
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• 2009

In this work, transparent conductive oxide(TCO) films such as $In_2O_3-SnO_2$(ITO) and $In_2O_3-ZnO$(IZO) were prepared on polyethylene naphthalene(PEN) and glass substrates by using rf-magnetron sputtering system. The TCO films deposited on PEN substrate show very poor conductivity as compared to that of the TCO films deposited on glass substrates. From the results of the residual gas analysis(RGA) test, this poor stability of plastic substrate is presumed to be caused by the deteriorated adhesion between the TCO films and the plastic substrate due to outgassing from the plastic substrate during deposition of TCO films. From our experiment, it is found that the vaporization of some defects in the plastic substrates deteriorate the adhesion of the TCO films to the plastic substrate, because the most plastic substrates containing the water vapor and/or other adsorbed particles such as organic solvents. Mixing of these gases vaporized in the sputtering process will also affect the electrical property of the deposited TCO films. Inorganic thin composite $(SiO_2)_{40}(ZnO)_{60}$ film as a gas barrier layer is coated on the PEN substrate to protecting the diffusion of vapors from the substrate, so that the TCO films with an improved quality can be obtained.

• Journal of the Korean Vacuum Society
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• v.4 no.S1
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• pp.168-173
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• 1995

$GaxIn{1_x}As$ epitaxial layers were grown by a simplified hydrode vapor phase epitaxy(VPE) method bsed on the utilization of Ga/In alloy as the source metal. The effects of a wide range of experimental variables(i.e.,inlet mole fraction of HCI, deposition temperature, Ga/In alloy composition) on the ternary composition and growth rate were investigated. Layers of $Ga_{0.47}In_{0.53}As$ lattice matched to InP were successfully grown from alloys containing 5 to 8 at.% Ga. These layers were used to produce state-of-the art p-i-n photodetectors having the following characteristics: dark current, $I_d$(-5V) = 10-20 nA: responsivity, R=0.84-0.86 A/W; dark current, Id(-5V)=10-20 nA; responsivity, R=0.84-0.86 A/W; capacitance, C=0.88-0.92 pF; breakdown voltage, $V_b$ >40V. This study demonstrated for the first time that a simplified hydride VPE process with a Ga/In alloy source is capable of producing device quality epitaxial layers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.236-238
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• 1997

A cellular power amplifier using an APCVD(Atmospheric Pressure Chemical Vapor Deposition)-grown SiGe base HBT of ETRI has been designed with a linear simulation CAD. The Si/SiGe HBT with an emitter area of 2$\times$8${\mu}{\textrm}{m}$$^2$typically has a cutoff frequency(f$_{T}$) of 7.0 GHz and a maximum oscillation frequency(f$_{max}$) of 16.1 GHz with a pad de-embedding A packaged power Si/SiGe HBT with an emitter area of 2$\times$8$\times$80${\mu}{\textrm}{m}$$^2$typically shows a f$_{T}$ of 4.7 GHz and a f$_{max}$ of 7.1 GHz at a collector current (Ic) of 115 mA. The power amplifier exhibits a Forward transmission coefficient(S21) of 13.5 dB, an input and an output reflection coefficients of -42 dB and -45 dB respectively. Up to now the III-V compound semiconductor devices hale dominated microwave applications, however a rapid progress in Si-based technology make the advent of the Si/SiGe HBT which is promising in low to even higher microwave range because of lower cost and relatively higher reproducibility of a Si-based process.ess.ess.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.15-16
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• 2006

The thermal stability of nickel silicide with compressively and tensilely stressed nitride capping layer has been investigated in this study. The Ni (10 nm) and Ni/Co/TiN (7/3/25 nm) structures were deposited on the p-type Si substrate. The stressed capping layer was deposited using plasma enhanced chemical vapor deposition (PECVD) after silicide formation by one-step rapid thermal process (RTP) at $500^{\circ}C$ for 30 sec. It was found that the thermal stability of nickel silicide depends on the stress induced by the nitride capping layer. In the case of Ni (10 nm) structure, the high compressive sample shows the best thermal stability, whereas in the case of Ni/Co/TiN (7/3/25 nm) structure, the high compressive sample shows the worst thermal stability.

• Journal of the Optical Society of Korea
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• v.15 no.4
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• pp.362-367
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• 2011

Organic ($Alq_3$) film, which was coated on a donor plate, was transferred to an organic light emitting diode (OLED) substrate with help of heat generated by a dithering laser beam. The laser beam was diffracted in an acousto-optic modulator (AOM), then focused on the laser-to-heat converting layer of the donor plate; the focused spot followed trajectories guided by rotation of a Galvano-mirror. Three different functional waveforms, sine wave, square wave, and saw tooth wave were applied to the AOM as modulation signal to generate the dithering beam. The fluorescence microscope images of the donor plate showed that the patterns of removed $Alq_3$ film were affected considerably by the modulation waveforms and the phase difference between adjacent dithering beams. Further, the printed images of Alq3 film on the OLED substrate were different from the patterns of removed Alq3 film. Atomic force microscope images indicated that not only direct transfer but also deposition by sublimated vapor of Alq3 contributed to the pattern formation. Printed patterns affected considerably the electricity-to-light conversion characteristics of OLEDs. For uniform transfer, not only the phase relation of dithering beam lines but also adequate waveform were important.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.893-896
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• 2003

Plasma polymerized para-xylene (PPpX) thin films deposited by plasma enhanced chemical vapor deposition (PECVD) were used to passivate the organic light emitting diodes (OLEDs). For OLEDs, indium tin oxide (ITO), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine (TPD), tris(8-hydroxyquinoline) aluminum $(Alq_{3})$ and aluminum (Al) were used as the anode, the hole transport layer (HTL), the emitting layer (EML) and the cathode, respectively. The OLED device with the PPpX passivation film (passivated device) showed similar electrical and optical characteristics to those of the OLED device without the PPpX passivation film (control device), indicating that the PECVD process did not degrade the performance of the OLEDs notably. The lifetime of the passivated device was two times longer than that of the control device. Passivation of OLEDs with PPpX films also suppressed the growth of dark spots. The density and size of dark spots of the passivated device were much smaller than those of the control device.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.8
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• pp.1-4
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• 2011

This study was the coorrelation between the electrical properties and the dielectric constant of organic inorganic hybrid type low k SiOC film. SiOC film as low-k films was deposited by the chemical vapor deposition and then annealed at 30 $0{\sim}500^{\circ}C$ to find out the properties of the depending on the temperature and polarity. SiOC film decreased the dielectric constant after annealing process, and the electrical properties were improved at the sample annealed at $400^{\circ}C$. From the XRD patterns, there were two kinds of bonding structures in SiOC film. There was the difference in the bonding structure between the samples annealed under $300^{\circ}C$ and the samples annealed over $400^{\circ}C$. The change was confirmed near $400^{\circ}C$.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.759-762
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• 2003

The epitaxially grown Mg-doped GaN thin film was prepared by MOCVD (Metal Organic Chemical Vapor Deposition) for a SAW(Surface Acoustic Wave) filter. Mg-doped GaN thin film had enough properties for a SAW filter which include crystallinity and morphology. The surface morphology and crystalline of the Mg-doped GaN thin films were characterized using AFM and an X-ray rocking curve. The SAW filter, which was fabricated by lift-off process and frequency response, was measured by HP 8753C network analyzer. Center frequency was 96.687 MHz and SAW velocity was 5801 m/s when wavelength(λ) was 60${\mu}{\textrm}{m}$. Insertion loss was over -10 dB, Q was factor over 200, and side lobe attenuation was over 22 dB which was suitable for use as a SAW filter. Electro-mechanical coupling coefficient (k$^2$) was calculated from the measured data. k$^2$ was from 1 % to 1.44 %. The fabricated SAW filter using Mg-doped GaN/sapphire structure has good qualities as a filter and will be used as a SAW filter for operating RF frequency.

• Composites Research
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• v.29 no.6
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• pp.375-378
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• 2016

Characteristics of nanocrystalline materials are known substantially dependent on the microstructure such as grain size, crystal orientation, and grain boundary. Thus it is desired to have systematic characterization methods on the various nanomaterials with complex geometries, especially in low dimensional nature. One of the interested nanomaterials would be a pure two-dimensional material, graphene, with superior mechanical, thermal, and electrical properties. In this study, mechanical properties of "polycrystalline" graphene were numerically investigated by molecular dynamics simulations. Subdomains with various sizes would be generated in the polycrystalline graphene during the fabrication such as chemical vapor deposition process. The atomic models of polycrystalline graphene were generated using Voronoi tessellation method. Stress strain curves for tensile deformation were obtained for various grain sizes (5~40 nm) and their mechanical properties were determined. It was found that, as the grain size increases, Young's modulus increases showing the reverse Hall-Petch effect. However, the fracture strain decreases in the same region, while the ultimate tensile strength (UTS) rather shows slight increasing behavior. We found that the polycrystalline graphene shows the reverse Hall-Petch effect over the simulated domain of grain size (< 40 nm).

• Steel and Composite Structures
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• v.23 no.2
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• pp.153-160
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• 2017

It is extremely important to be aware of the ballistic performances of engineering materials in order to be able to choose the lightest armor providing full ballistic protection in civil and military applications. Therefore, ballistic tests are an important part of armor design process. In this study, ballistic performance of plates made of carbon steel and cold worked tool steel against 7.62 mm AP (armor-piercing) bullets was examined experimentally and numerically in accordance with NIJ standards. Samples in different sizes were prepared to demonstrate the effect of target thickness on ballistic performance. Some of these samples were coated with titanium nitride using physical vapor deposition (PVD) method. After examining all successful and unsuccessful samples at macro and micro levels, factors affecting ballistic performance were determined. Explicit non-linear analyses were made using Ls-Dyna software in order to confirm physical ballistic test results. It was observed that the ballistic features of steel plates used in simulations comply with actual physical test results.