• Journal of Korea Society of Industrial Information Systems
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• v.19 no.4
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• pp.9-16
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• 2014

Electrode contact resistance is a crucial factor in physiological measurements and can be an accuracy limiting factor to perform electrical impedance measurements. The electrical bio-impedance values can be calculated by the conductivity and permittivity of underlying tissue using implant electrode in human skin. In this study we focus on detecting physiological changes in the human skin layers such as the sebum layer, stratum corneum layer, epidermis layer, dermis layer, subcutaneous fat and muscle. The aim of this paper is to obtain optimal design for implantable electrode at subcutaneous fat layer through the simulation by finite element methods(FEM). This is achieved by evaluating FEM simulations geometrically for different electrodes in length(50 mm, 70 mm), in shape(rectangle, round square, sexangle column), in material(gold) and in depth(22.325 mm) based on the information coming from the subcutaneous fat layer. In bio-impedance measurement experiments, according to electrode shapes and applied voltage, we have ascertained that there was the highest difference of bio-impedance in subcutaneous fat layer. The methodology of simulation can be extended to account for different electrode designs as well as more physical phenomena that are relevant to electrical impedance measurements of skin and their interpretation.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.11
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• pp.1-5
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• 2010

We developed a novel micro-electro mechanical systems (MEMS) test socket using silicon on insulator (SOI) substrate with the cantilever array structure. We designed the round shaped cantilevers with the maximum length of $350{\mu}m$, the maximum width of $200{\mu}m$ and the thickness of $10{\mu}m$ for $650{\mu}m$ pitch for 8 mm x 8 mm area and 121 balls square ball grid array (BGA) packages. The MEMS test socket was fabricated by MEMS technology using metal lift off process and deep reactive ion etching (DRIE) silicon etcher and so on. The MEMS test socket has a simple structure, low production cost, fine pitch, high pin count and rapid prototyping. We verified the performances of the MEMS test sockets such as deflection as a function of the applied force, path resistance between the cantilever and the metal pad and the contact resistance. Fabricated cantilever has 1.3 gf (gram force) at $90{\mu}m$ deflection. Total path resistance was less than $17{\Omega}$. The contact resistance was approximately from 0.7 to $0.75{\Omega}$ for all cantilevers. Therefore the test socket is suitable for BGA integrated circuit (IC) packages tests.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.102-108
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• 2013

In manufacturing of solution-processed organic electronic devices, a spin coating method is frequently used, but which has a big problem. Solvent in a solution has a decisive effect such as physical and chemical damage for successive solution-based film deposition. Such a severe damage by solvent restricts for fabricating building blocks of multi-layered films from solutions. In this work, it will be shown that a proper combination of well-known solvents gives a chance to fabricate multi-layered film, also this new method was applied to make organic field effect transistor. Two types of bottom gate, bottom contact transistors were fabricated, one of which is fabricated by conventional single spin coating method, the other fabricated by double spin coating method. Compared with the electrical characteristics in a single spin coated transistor, the leakage current between source and gate electrode was decreased, ON state current was increased, and the extracted saturation mobility was multiplied more than 2.7 time for double spin coated transistors. It is suggested that the multiple coated gate dielectric structure is more desirable for high performance organic ferroelectric field effect transistors.

• Composites Research
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• v.24 no.1
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• pp.45-50
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• 2011

Transparent and conductive carbon nanotube on polyethylene terephthalate (PET) were prepared by dip-coating method for self-sensing multi-functional nanocomposites. The changes in the electrical and optical properties of CNT coating mainly depended on the number of dip-coating, concentration of CNT solution. Consequently, the surface resistance and transmittance of CNT coating were sensitively controlled by the processing parameters. Surface resistance of CNT coating was measured using four-point method, and surface resistance of coated CNT could be better calculated by using the dual configuration method. Optical transmittance of PET film with CNT coating was evaluated using UV spectrum. Surface properties of coated CNT investigated by wettability test via static and dynamic contact angle measurement were consistent with each other. As dip-coating number increased, surface resistance of coated CNT decreased seriously, whereas the transmittance exhibited little lower due to the thicker CNT networks layer. Interfacial microfailure properties were investigated for CNT and indium tin oxide (ITO) coatings on PET substrates by electrical resistance measurement under cyclic loading fatigue test. CNT with high aspect ratio exhibited no change in surface resistance up to 2000 cyclic loading, whereas ITO with brittle nature showed a linear increase of surface resistance up to 1000 cyclic loading and then exhibited the level-off due to reduced electrical contact points based on occurrence of many micro-cracks.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.429-429
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• 2007

For various applications of liquid crystal displays (LCDs), the uniform alignment of liquid crystal (LC) molecules on treated surfaces is significantly important. Generally, a rubbing method has been widely used to align the LC molecules on polyimide (PI) surfaces. Rubbed PI surfaces have suitable characteristics, such as uniform alignment. However, the rubbing method has some drawbacks, such as the generation of electrostatic charges and the creation of contaminating particles. Thus, we strongly recommend a non contact alignment technique for future generations of large high-resolution LCDs. Most recently, the LC aligning capabilities achieved by ultraviolet and ion-beam exposures which are non contact methods, on diamond-like carbon (DLC) inorganic thin film layers have been successfully studied because DLC thin films have a high mechanical hardness, a high electrical resistivity, optical transparency, and chemical inertness. In addition, nitrogen-doped DLC (NDLC) thin films exhibit properties similar to those of the DLC thin films and a higher thermal stability than the DLC thin films because C:N bonding in the NDLC thin filmsis stronger against thermal stress than C:H bonding in the DLC thin films. Our research group has already studied the NDLC thin films by an ion-beam alignment method. The $SiN_x$ thin films deposited by plasma-enhanced chemical vapor deposition are widely used as an insulation layer for a thin film transistor, which has characteristics similar to those of DLC inorganic thin films. Therefore, in this paper, we report on LC alignment effects and pretilt angle generation on a $SiN_x$, thin film treated by ion-beam irradiation for various N ratios

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.2
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• pp.267-278
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• 2019

Variety of tunnel ahead prediction methods have been performed for safe tunnel construction during tunnel excavation. Pole-pole array among the electrical resistivity survey, which is one of the tunnel ahead prediction method, has been utilized to predict water-bearing sediments or weak zone located within 5 times of tunnel diameter. One of the most important processes is the estimation of virgin ground resistivity and it can be obtained from the following process: 1) calculation of contact area between the electrodes and the medium, and 2) assumption of the electrodes as equivalent spherical electrodes which have a same surface area with the electrodes. This assumption is valid in a small contact area and sufficient distance between the electrodes. Since the measured resistance, in general, varies with the electrode size, shape, and distance between the electrodes, it is necessary to evaluate the influence of these factors. In this study, theoretical equations were derived and experimental tests were conducted considering the electrode size, shape, and distance of cylindrical electrodes which is the most commonly utilized electrode shape. Through this theoretical and experimental study, it is known that one should be careful to use the assumption of the equivalent half-spherical electrode with large ratio between the penetrated depth and radius of the cylindrical electrode, as the error may get larger.

• Korean Journal of Materials Research
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• v.28 no.4
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• pp.195-200
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• 2018

This study investigated the effects of the post annealing temperatures on the electrical and interfacial properties of a metal-semiconductor-metal photodetector(MSM-PD) device. The interdigitate type MSM-PD devices had the structure Al(500 nm) / Ti(200 nm) / poly-Si(500 nm). Structural analyses of the MSM-PD devices were performed by employing X-ray diffraction(XRD), scanning electron microscopy(SEM) and transmission electron microscope(TEM). Electrical characteristics of the MSM-PD were also examined using current-voltage(I-V) measurements. The optimal post annealing condition for the Schottky contact of MSM-PD devices are $350^{\circ}C$-30minutes. However, as the annealing temperature and time are increased, electrical characteristics of MSM-PD device are degraded. Especially, for the annealing conditions of $400^{\circ}C$-180minutes and $500^{\circ}C$-30minutes, the I-V measurement itself was impossible. These results are closely related to the solid phase reactions at the interface of MSM-PD device, which result in the formation of intermetallic compounds such as $Al_3Ti$ and $Ti_7Al_5Si_{12}$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.4
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• pp.285-296
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• 2005

Reduced pressure chemical vapor deposition technology has been used to study SiGe heterostructure epitaxy and device issues, including SiGe relaxed buffers, proper control of Ge component and crystalline defects, two dimensional delta doping, and their influence on electrical properties of devices. From experiments, 2D profiles of B and P presented FWHM of 5 nm and 20 nm, respectively, and doses in 5×10/sup 11/ ∼ 3×10/sup 14/ ㎝/sup -2/ range. The results could be employed to fabricate SiGe/Si heterostructure field effect transistors with both Schottky contact and MOS structure for gate electrodes. I-V characteristics of 2D P-doped HFETs revealed normal behavior except the detrimental effect of crystalline defects created at SiGe/Si interfaces due to stress relaxation. On the contrary, sharp B-doping technology resulted in significant improvement in DC performance by 20-30 ％ in transconductance and short channel effect of SiGe HMOS. High peak concentration and mobility in 2D-doped SiGe heterostructures accompanied by remarkable improvements of electrical property illustrate feasible use for nano-sale FETs and integrated circuits for radio frequency wireless communication in particular.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.1
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• pp.136-142
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• 2015

In the paper, a design method of knee and pelvis joint in the biped robot is proposed for shock absorption and gravity compensation. Similarly to the human's body, the knee joints of the biped robot support most body weight and get a shock from the landing motion of the foot on the floor. The torque of joint motor is also increased sharply to keep the balance of the robot. Knee and pelvis joints with the spring are designed to compensate the gravity force and reduce the contact shock of the robot. To verify the efficiency of the proposed design method, we develope a biped robot with the joint mechanism using springs. At first, we experiment with the developed robot on the static motions such as the bent-knee posture both without load and with load on the flat ground, and the balance posture on the incline plane. The current of knee joint is measured to analyze the impact force and energy consumption of the joint motors. Also, we observe the motor current of knee and pelvis joints for the walking motion of the biped robot. The current responses of joint motors show that the proposed method has an effect on shock reduction and gravity compensation, and improve the energy efficiency of walking motions for the biped robot.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.9
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• pp.1323-1329
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• 2015

The WO₃/Ag/WO₃ transparent thin films are fabricated by the RF magnetron sputtering. This has a transmittance of front and rear about 90% in the visible light range and surface resistance of 6.41Ω/□. In this paper, we analyzed the surface characteristics caused by the working pressure and O₂ plasma surface treatment to apply a transparent electrode that was prepared to the laminated structure with other materials. The working pressure was changed in the WO₃ film to 10mTorr, 7mTorr, and 5mTorr, it showed a lower than roughness of conventional ITO. In addition, by 55.5774 J/m² at 5mTorr, it shows the hydrophobic property with lower process pressure. O₂ plasma surface treatment was changed at the condisions of the RF power to 150W, 100W, and 50W and the process time to 240s, 180s, 120s, and 60s. The surface roughness are the maximum roughness(Rmax) 6.437nm and the average roughness(Rq) 0.827nm at RF power 150W, and the maximum roughness (Rmax) 6.880nm and the average roughness (Rq) 0.839nm at process time 240sec. It showed a lower value than the surface treatment. also about working pressure and process time is increased, it showed the hydrophobic.