• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.215-219
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• 2004

Metal-chelate derivatives have been investigated intensively as an emitting layer and recognize to have excellent electroluminescence(EL) properties. We synthesized new luminescent material, 1,4-dihydoxy-5,8-naphtaquinone $Aiq_3$ complex($Al_2Nq_4$) and investigated the electrical optical properties. OLED has potential candidates for information display with merits of thickness, low power and high efficiency. Although the OLED show a lot of advantages for information display, it has the limit of inorganic(metal)/ organic interface. In this study, the two methods are used to study the interface of metal/organic in OLED. First, we treated $O_2$ plasma on an ITO thin film by using RIE system, and analyzed the ingredient of ITO thin film according to change of the processing conditions. We used the RDS and the XPS for the ingredient analysis of the surface and bulk. We measured electrical resistivity using Four-Point-Probe and calculated sheet resistance, and ITO surface roughness was measured by using AFM. We fabricated OLED using substrate that was treated optimum ITO surface. Second, we used the buffer layer of CuPc to improve the characteristics of the interface and the hole injection in OLED. The result of the study for electrical and optical properties by using I V L T System(Flat Panel Display Analysis System), we confirmed that the electrical properties and the luminance properties were improved.

• Journal of Sensor Science and Technology
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• v.25 no.1
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• pp.46-50
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• 2016

During KSTAR plasma experiments, torsional $Alfv\acute{e}n$ waves in the frequency of few GHz or below were detected. To understand this plasma waves during the crash of MHD instabilities, an RF spectrometer has been developed for detection of the radiated RF signals in the KSTAR Tokamak. It has the capability of broadband RF spectral measurement (50 ~ 400 MHz). To detect the broadband RF signals which are radiated from the KSTAR systems, a broadband antenna is the key feature of the RF spectrometer. In this paper, a broadband bowtie antenna for detection of $Alfv\acute{e}n$-waves in the KSTAR Tokamak is presented. Planar-type bowtie antenna is designed and fabricated on an FR4 substrate with thickness of 1.6 mm. The antenna consists of bowtie shaped balanced radiators and broadband planar balun. The antenna is designed to have an input impedance of 50 Ohm, and a taper-shaped balun is adopted for field and impedance matching between 50 Ohm transmission line to 110 Ohm feeding network of balanced radiators. The implemented antenna provides around -3 to 3 dBi of gain for the whole frequency band. The VSWR of the bowtie antenna is less than 12:1 over the frequency bandwidth of 50 to 2000 MHz.

• Journal of Sensor Science and Technology
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• v.25 no.6
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• pp.383-387
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• 2016

Well-ordered nanocolumnar indium oxide ($In_2O_3$) thin films have been successfully fabricated by glancing angle deposition (GAD) using an e-beam evaporator. Nanocolumnar structures have a porous and large surface area with a narrow neck between nanocolumns, which allows them to detect minute amounts of gases. The nanocolumnar $In_2O_3$ thin films were fabricated by the GAD process at five different positions, viz. top, bottom, center, left, and right in a four inch substrate holder. There was a divergence in the thickness and the base resistance of each sensor. However, all the sensors exhibited extremely high sensitivity that was greater than $10^3$ times the change in electrical resistance after being exposed to 50 ppm of acetone gas at $300^{\circ}C$. Furthermore, the nanocolumnar $In_2O_3$ sensors displayed an extremely low detection limit (1.2 ppb) in dry atmosphere as well as in high humidity (80%). We demonstrated that the GAD nanocolumnar $In_2O_3$ sensors have an enormous potential for many applications owing to their particularly simple and reliable fabrication process.

• Journal of Sensor Science and Technology
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• v.15 no.4
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• pp.237-244
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• 2006

Atomic force microscope (AFM) has become a common tool for the structural and physical studies of biological macromolecules, mainly because it provides the ability to perform experiments with samples in a buffer solution. In this study, structure of proteins and nucleic acids has been studied in their physiological environment that allows native intermolecular complexes to be formed. Cr and Au were deposited on p-Si (100) substrate by thermal evaporation method in sequence with the thickness of $200{\AA}$ and $500{\AA}$, respectively, since Au is adequate for immobilizing biomolecules by forming a self-assembled monolayer (SAM) with semiconductor-based biosensors. The SAM, streptavidin and biotin interacted each other with their specific binding energy and their adsorption was analyzed using the Bio-AFM both in a solution and under air environment. A silicon nitride tip was used as a contact tip of Bio-AFM measurement in a solution and an antimony doped silicon tip as a tapping tip under air environment. Actual morphology could also be obtained by 3-dimensional AFM images. The length and agglomerate size of biomolecules was measured in stages. Furthermore, $R_{a}$ (average of surface roughness) and $R_{ms}$ (mean square of surface roughness) and surface density for the adsorbed surface were also calculated from the AFM image.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.3
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• pp.686-693
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• 2004

We have studied a method to fabricated a Surface Acoustic Waves (SAW) filter for Wide band Codeless Division Multiple Access(WCDMA) was formed on the Langasite substrate and was evaporated by Aluminum-Copper alloy and then we developed a simulator using the mathematica package. And, we can design and fabricate the Slanted finger Inter-digital Transducer (SFIT) for the purpose to decreased the ultimate rejections on side of the electrodes, and performed computer-simulation by simulator. Also, we have employed that the block weighted type Inter-digital Transduce(IDT) as input transduce of the filter and the withdrawal weighted type IDT as an output transducer of the filter in order to minimize effect of diffractions. We have employed that the number of pairs of the input and output IDT are 50 pairs and the thickness and the width of reflector are $5000\AA$, and $1\lambda/4(\cong3.6{\mu}m)$, respectively. Also the width of IDT' finger and the space between IDT' finger and reflector are $1\lambda$/16 and 1\lambda$/8, respectively. Frequency response of the fabricated SAW bandpass filter has the property that center frequency is about 190MHz, bandwidth at the 3dB is probably 4MHz and out-band attenuation is -60dB approximately.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2359-2366
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• 2014

In this paper, the characteristics of a inset fed rectangular microstrip patch antenna for S-band applications is studied. The variations of return loss along inset length and inset width are investigated on the inset fed rectangular microstrip patch antenna. From the investigated results, the optimized inset fed antenna is designed. At the resonant frequency 2.3 GHz, the optimized dimension of the patch is $45.0mm{\times}40.9mm$. The inset length and width are 14 mm and 1 mm, respectively. The designed antenna is fabricated on the substrate which has a dielectric constant and thickness with 2.5 and 0.787 mm. Simulation results are obtained by a 3D EM(Electromagnetic) solver. The resonant frequency and return loss are measured 2.3025 GHz and -21.11 dB, respectively. The measured and simulated results of the fabricated antenna are in good agreement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.3
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• pp.1445-1450
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• 2013

In this paper, a broadband series-fed bow-tie dipole pair (SBDP) antenna operating in the band of 1.7-2.7 GHz for mobile communication base station applications is proposed. The proposed antenna uses bow-tie-shaped dipole elements instead of straight strip dipole ones used in a conventional series-fed dipole pair (SDP) antenna. The simulation results show that the lowest operating frequency is shifted toward lower frequency as the flare angle increases, and so the lengths of the bow-tie dipole elements can be reduced in proportion to the frequency shift toward lower frequency. An SBDP antenna with a flare angle of 10 degrees is fabricated on an FR4 substrate (dielectric constant = 4.4 and thickness = 1.6 mm) and total width of the fabricated antenna is reduced by 10% compared to that of the conventional SDP antenna. The measured impedance bandwidth for voltage standing wave ratio (VSWR) < 2 is 48.8% (1.69-2.78 GHz), gain is 5.8-6.3 dBi, and the front-to-back ratio (FBR) is 14-17 dB.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.6
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• pp.1106-1115
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• 2006

In this paper, the transmission characteristics and equivalent circuit model of microstrip transmission line having defected ground structure (DGS) in multilayer substrates are described fur high frequency region. In order to perform the study, the second dielectric layer is attached additionally onto the bottom(ground) plane of the basic DGS microstrip line consisted of the microstrip line and DGS. The dielectric constant and thickness of the second dielectric layer are adjusted to get various transmission characteristics and model parameters, and to analysis the effect of the second dielectric layer ultimately. According to this paper, the effect and equivalent circuits due to the attached dielectric substrate are verified separately, and this is expected to be applied to high frequency circuit design in the future.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.141-142
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• 2005

To investigate the ZnO thin films which is interested in the next generation of short wavelength LEDs and Lasers, our ZnO thin films were deposited by RF sputtering system. At sputtering process of ZnO thin films, substrate temperature, work pressure respectively is $300^{\circ}C$ and 5.2 mTorr, and the purity of target is ZnO 5N. The thickness of ZnO thin films was about $1.9{\mu}m$ at SEM analysis after sputtering process. Phosphorus (P) and arsenic (As) were diffused into ZnO thin films sputtered by RF magnetron sputtering system in ampoule tube which was below $5\times10^{-7}$ Torr. The dopant sources of phosphorus and arsenic were $Zn_3P_2$ and $ZnAs_2$. Those diffusion was perform at 500, 600, and $700^{\circ}C$ during 3hr. We find the condition of p-type ZnO whose diffusion condition is $700^{\circ}C$, 3hr. Our p-type ZnO thin film has not only very high carrier concentration of above $10^{19}/cm^3$ but also low resistivity of $5\times10^{-3}{\Omega}cm$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.448-449
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• 2006

For the possible applicative pearl pigment, multi-layered $TiO_2/Al/TiO_2$, $TiO_2/Cr/TiO_2$ thin film was deposited on glass substrate by using sputtering method. $TiO_2$ and Al or Cr was selected as a possible high and low refraction materials at the film interface respectively. Optical properties including color effect were systematically studied in terms of different film thickness and film layers by using spectrometer. In order to expect the experimental results, the simulation program, the Essential Macleod Program(EMP) was adopted and compared with the experimental data. The film consisting of $TiO_2/Al/TiO_2$, $TiO_2/Cr/TiO_2$ layers show the wavelength range of 430 - 760nm, typically color ranges between bluish purple and red. It was confirmed that this experimental result was quite well matched with the experimental one.