• Progress in Superconductivity
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• v.4 no.1
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• pp.74-79
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• 2002

High-speed probe made to test single flux quantum(SFQ) circuits was comprised of semi-rigid coaxial cables and microstrip lines. The impedance was set at 50 $\Omega$to carry high-speed signals without much loss. To do performance test of high-speed probe, we have attempted to fabricate a test chip which has a coplanar waveguide(CPW) structure. Electromagnetic simulation was done to optimize the dimension of CPW so that the CPW structure has an impedance of 50$\Omega$, matching in impedance with the probe. We also used the simulation to investigate the effect of the width of signal line and the gap between signal line and ground plane to the characteristics of CPW structure. We fabricated the CPW structure with a gold film deposited on Si wafer whose resistivity was above $1.5\times$10$_4$$\Omega$.cm. The magnitudes of S／sub 21／ of CPW at 6 ㎓ in simulations and in the actual measurements done with a network analyzer were: -0.1 ㏈ and -0.33 ㏈ (type A),-0.2 ㏈ and -0.48 ㏈ (type B), respectively. Using the test chip, we have successfully tested the performance of high-speed probe made for SFQ circuits. The probe showed the good performance overthe bandwidth of 10 ㎓.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.277-277
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• 2012

PCDTBT (Poly[N-9''-hepta-decanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)]) is an attractive material as a semiconducting polymer for organic thin film transistor (OTFT) and organic solar cell (OSC). High power conversion efficiency (~6%) under simulated AM 1.5G solar illumination of bulk-heterojunction solar cell with PCDTBT and [6,6]-phenyl C60 butyric acid methyl ester (PC61BM) blend was reported. In OSC, it is known that the band alignment at the interface between donor and acceptor is critical. Therefore, we studied the interfacial electronic structures of PCDTBT and PC61BM. The polymers are deposited by electro-spray on gold and In-situ x-ray and ultraviolet photoelectron spectroscopy measurements revealed the interfacial electronic structures. We obtained the energy level alignment between two materials and the different interface formation was observed with different deposition order.

• Journal of the Korean Society of Safety
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• v.19 no.3 s.67
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• pp.51-56
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• 2004

Conductive polymer blends and composites are widely used for different safety application such as electrostatic charge dissipation(ESD), electromagnetic interference(EMI) shielding, electrostatic prevention and safety chemical sensor. In order to prepare a impedance-type humidity sensor that is durable at high humidities and high temperature, electically conductive polymer blends based on diallyldimethylammonium chloride(DADMAC) and epoxy were prepared in this study. The polymer blends type conductive ionomer exhibits reaction each other DADMAC and epoxy in FT-IR and DSC analysis. The blends material was traced by new peak at 1600cm-1 and appeard improvement of thermal resistance by melting point shift. Alumina substrate was deposited a pair of gold electrodes by screen printing. The blend material were spin-coated with a thin film type on the surface of alumina substrate. The polymer bleld type sensor exhibits a linear impedance increasing better than DADMAC coated humidity sensor. Also it shows good sensitivity, low hysteresis and durability against high humidity.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.7
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• pp.375-381
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• 2000

In this paper, we described the characterization of High-Tc Superconducting(HTS) microstrip antenna using non-radiating edge feeding technique and reported the microwave properties of HTS antennas with temperature. To do this, we prepared the $YBa_2Cu_3O_{7-x}$ superconducting thin film on MgO substrate using pulse-laser deposition techniques. The HTS microstrip antenna using non-radiating feeding technique was fabricated using chemical wet-etching. Then it was compared with identical antenna patterned with evaporated gold. The diverse measured results have been reported in terms of the input impedance, resonant frequency and return loss. In additional, at around the critical temperature, the effect of kinetic inductance which affect the resonant characteristic of the HTS microstrip antenna was reported.

• Proceedings of the KIEE Conference
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• 2000.11c
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• pp.455-457
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• 2000

In this work the electrical characteristics of organic TFTs with the semiconductor-insulator interfaces, where the gate dielectrics were treated by the two methods which are the deposition of Octadecyltrichlorosilane (OTS) on the insulator and rubbing the insulator surface. Pentacene is used as an active semiconducting layer. The semiconductor layer of pentacene was thermally evaporated in vacuum at a pressure of about $2{\times}10^{-7}$ Torr and at a deposition rate of $0.3{\AA}/sec$. Aluminum and gold were used for the gate and source/drain electrodes. OTS is used as a self-alignment layer between $SiO_2$ and pentacene. The gate dielectric surface was rubbed before pentacene is deposited on the insulator. In order to confirm the changes of the surface morphology the atomic force microscopy (AFM) was utilized. The characteristics of the fabricated TFTs are measured to clarify the effects of the surface treatment.

• Journal of the Optical Society of Korea
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• v.18 no.2
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• pp.174-179
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• 2014

Since in vitro neural recording and imaging applications based on a surface plasmon resonance (SPR) technique have expanded dramatically in recent years, cytotoxicity assessment to ensure the biosafety and biocompatibility for those applications is crucial. Here, we report the cytotoxicity of the SPR substrate incorporating a flint glass whose refractive index is larger than that of a conventional crown glass. A high refractive index glass substrate is essential in neural signal detection due to the advantages such as high sensitivity and wide dynamic range. From experimental data using primary hippocampal neurons, it is found that a lead-based flint glass is not appropriate as a neural recording template although the neuron cells are not directly attached to the toxic glass. We also demonstrate that the adhesion layer between the glass substrate and the gold film plays an important role in achieving the substrate stability and the cell viability.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.1
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• pp.15-21
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• 2013

In this paper, a MEMS tunable capacitor was successfully designed and fabricated using an aluminum nitride film and a gold suspended membrane with two air gap structure for commercial RF applications. Unlike conventional two-parallel-plate tunable capacitors, the proposed tunable capacitor consists of one air suspended top electrode and two fixed bottom electrodes. One fixed and the top movable electrodes form a variable capacitor, while the other one provides necessary electrostatic actuation. The fabricated tunable capacitor exhibited a capacitance tuning range of 375% at 2 GHz, exceeding the theoretical limit of conventional two-parallel-plate tunable capacitors. In case of the contact state, the maximal quality factor was approximately 25 at 1.5 GHz. The developed fabrication process is also compatible with the existing standard IC (integrated circuit) technology, which makes it suitable for on chip intelligent transceivers and radios.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.7
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• pp.864-870
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• 1999

An experimental study Is conducted in a four-vane linear cascade in order to examine the influence of the wake behind rectangular bars on the flow and heat transfer characteristics. Flow and heat transfer measurements are made for the inlet Reynolds number of 66000(based on chord length and free-stream velocity). Turbulent intensity and stress are measured using a hot-wire anemometer, and to measure the convective heat transfer coefficients on the blade surface liquid crystal/gold film Intrex technique is used. Each of experimental cases is characterized by the unsteadiness measured at the entrance of the cascade. The wake behind the rectangular bars enhances the turbulent motion of the flow in the cascade passage. It also promotes the boundary layer development and transition. The results show that heat transfer coefficients on the blade surface increase with increasing unsteadiness.

• Journal of Surface Science and Engineering
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• v.52 no.6
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• pp.342-349
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• 2019

Titanium nitride(TiN) thin films have been deposited on PEN(Polyethylene naphthalate) substrate by reactive RF(13.56 MHz) magnetron sputtering in a 25% N₂/Ar mixed gas atmosphere. The pulsed DC bias voltage of -50V on substrates was applied with a frequency of 350 kHz, and duty ratio of 40%(1.1 ㎲). The effects of pulsed DC substrate bias voltage on the crystallinity, color, electrical properties of TiN_x films have been investigated using XRD, SEM, XPS and measurement of the electrical properties such as electrical conductivity, carrier concentration, mobility. The deposition rates of TiN_x films was decreased with application of the pulsed DC substrate bias voltage. The TiN_x films deposited without and with pulsed bias of -50V to substrate exhibits gray and gold colors, respectively. XPS depth profiling revealed that the introduction of the substrate bias voltage resulted in decreasing oxygen concentration in TiN_x films, and increasing the electrical conductivities, carrier concentration, and mobility to about 10 times, 5 times, and 2 times degree, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.310.1-310.1
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• 2013

We show the novel hot electron based-solar energy conversion using tandem structured Schottky diode with double Schottky barriers. In this report, we show the effect of the double Schottky barriers on solar cell performance by enhancing both of internal photoemission and band-to-band excitation. The tandem structured Au/Si diode capped with TiO2 layer as second semiconductor exhibited improved ability for light harvesting. The proposed mechanisms consist of multiple reflections of hot electrons and additional pathway of solar energy conversion due to presence of multiple interfaces between thin gold film and semiconductors. Short-circuit photocurrent measured on the tandem structured Au/Si diodes under illumination of AM1.5 increased by approximately 70% from 3.1% to 5.3% and overall incident photon to electron conversion efficiency (IPCE) was enhanced in visible light, revealing that the concept of the double Schottky barriers have significant potential as novel strategy for light harvesting.