• Electrical & Electronic Materials
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• v.7 no.5
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• pp.376-382
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• 1994

In this study we developed a program(DEVSIM) to simulate the two dimensional distribution of the electrostatic potential and the electric field of the arbitrary structure consisting of GaAs/AlGaAs semiconductor and metal as well as dielectric. By the comparision of the electric field distribution of GaAs MESFETs with the various recess gates we proposed a suitable device structure to improve the breakdown characteristics of MESFET. According to the results of simulation the breakdown characteristics were improved as the thickness of the active epitaxial layer was decreased. And the planar structure, which had the highly doped layer under the drain for the ohmic contact, was the worst because the highly doped layer prevented the space charge layer below the gate from extending to the drain, which produced the narrow spaced distribution of the electrostatic potential contours resulting in the high electric field near the drain end. Instead of the planar structure with the highly doped drain the recess gate structure having the highly doped epitaxial drain layer show the better breakdown characteristics by allowing the extention of the space charge layer to the drain. Especially, the structure in which the part of the drain epitaxial layer near the gate show the more improvement of the breakdown characteristics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.5
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• pp.418-423
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• 2003

AC loss is an important issue in the design of high-T$\sub$c/ superconducting power cables which consist of a number of Bi-2223 tapes wound on a former. In the cables, the tapes have different critical currents intrinsically. And they are electrically connected to each other and current leads. These make loss measurements considerably complex, especially for short samples of laboratory size. So special cautions are required in the positioning of voltage leads for measuring the true loss voltage. In this work we have prepared a conductor composed of three Bi-2223 tapes with different critical currents. The critical current and AC loss characteristics in the conductor have experimentally investigated. The results show that for uniform current distributions the conductor's critical current is proportional to the critical current of the Bi-2223 tape to which a voltage lead is attached. However it depends on the current non-uniformity parameter in the conductor rather than the tape's critical currents for nonuniform current distributions. The loss tests indicate that the AC loss is dependent on arrangements of voltage leads but not on their contact positions. The measured losses in the conductor also agree well with the sum of the transport losses measured in each Bi-2223 tape.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05a
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• pp.40-44
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• 2002

The increase of vehicles stagnations leads to the increasing attention to the way customers pay and a large number of projects on electronic cash system. Transport system is comprised of a number of advanced technologies, including information processing, communications, control, and electronics. Recently many research on a system which provides contact in order to protect driver's vehicle passage have been carried out. And some potential problems from that system are being reviewed by electronic cash system. In this papers, we suggest RF protocol developing technology using the concept of electronic cash. ATM electronic cash developing is consist of component of pre-developed coin throw, integration of component using its, and production of more requirement-satisfactory ITS solution. Result increase 15~40% pre-type vehicles stagnations. Especially, we expect this proposed concept would be well adapted to our national environments.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.9
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• pp.687-692
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• 2011

Hafnium oxide ($HfO_2$) was very advantageous for substitute material of gate on existing transistor. $HfO_2$ has been widely studied due to high contact with polysilicon and thermal stability and also, it is easily etched by using HF solution. In this study, $HfO_2$ and thermal oxide films were etched by wet etch method using chemical etchant. Etch rate of $HfO_2$ and thermal oxide was linearly increased with increasing concentration of HF and temperature but etch rate of $HfO_2$ was higher than thermal oxide due to $H^+$, $F^-$, and $HF_2^-$ ions at below 0.5% concentration of HF. And also, etch selectivity was improved by adding Hydrazine as additive.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.8
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• pp.514-519
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• 2017

TiN (titanium nitride) films were prepared using the RF magnetron sputtering technique. The films were deposited by pure $N_2$ plasma sputtering. Their mechanical properties, such as nano-indentation hardness, friction coefficient, and surface wettability, have been investigated. X-ray diffraction (XRD) studies revealed that the orientation of $TiN_X$ films changed towards the (111) orientation with decreasing working pressure due to a strong compressive stress during deposition. The strongest TiN (111) orientation was found when the film was deposited at a working pressure of 1 Pa. This film showed the largest hardness (16 GPa) and smallest friction coefficient (0.17) among the studied samples. Moreover, this film was found to be accompanied by a water-repellent surface with water contact angle more than $100^{\circ}$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.12
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• pp.1776-1781
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• 2015

Electric power trains receive electric power from overhead cables via a pantograph system. Power collector system in trains increase the cross section of tunnel and require a massive coreless filter reactor in propulsion inverter because of the power disturbance by contact loss phenomenon of a train. In this paper we proposed a wireless train which can run to next station with charging energy of ultra-capacitor module block. We designed DC-DC converter to charge and discharge ultra-capacitor modules by using Next Train running test results and confirm the feasibility of the proposed system through simulation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.11
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• pp.908-913
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• 2000

CoSi$_2$/p+/n diodes(bilayer diodes) were fabricated by using epitaxial CoSi$_2$grown from Co/Ti bilayer as a diffusion source. The I-V characteristics of p+/n diodes were measured and compared with those of diode made from Co monolayer (monolayer diode). Monolayer diodes showed typical p+n junction characteristics with the leakage current of as low as 10$^{-12}$ A and forward current 6-orders higher than the leakage current, when drive-in annealed at 90$0^{\circ}C$ for 20 sec.. On the other hand, bilayer diodes showed the Schottky-like behaviors with forward currents rather higher than those of monolyer diodes, but with too high leakage currents, when drive-in annealed at $700^{\circ}C$ or higher. However, when the annealing temperature was lowered to $700^{\circ}C$ and annealing time was increased to 60 sec., the leakage current was reduced to 10$^{-11}$ A and thus sho3wed typical diode characteristics. The high leakage currents for diodes annealed at $700^{\circ}C$ or higher was attributed to Shannon contacts formed due to unremoved Co-Ti-Si precipitates. But when annealed at 50$0^{\circ}C$, B ions diffused in the direction of the surface layer, and thus the leakage currents were reduced by removing Shannon contacts.

• Journal of the Korean institute of surface engineering
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• v.45 no.2
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• pp.81-88
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• 2012

Probe tip, which should have not only superior electrical characteristics but also good abrasion resistance for numerous contacts with semiconductor pads to confirm their availability, is essential for MEMS probe card. To obtain good durability of probe tip, it needs thick and crack-free rhodium layer on the tip. However, when the rhodium thickness deposited by electroplating increased, unwanted cracks by high internal stress led to serious problem of MEMS probe tip. This article reported the method of thick Rh deposition with Au buffer layer on the probe tip to overcome the problem of high internal stress and studied mechanical and electrical properties of that. MEMS probe tip with double-Rh layer had good contact resistance and durability during long term touch downs.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.10
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• pp.1448-1454
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• 2014

In this study, a new type of electrode device is implemented to measure the capacitance energy and interpret it as the ECG (Electrocardiogram) data. The main idea of this new electrode system is to estimate the capacitance on the skin by assembling a capacitive-coupled circuits and translate into the ECG signal. To measure the coupling energy and estimate the aquired data in terms of heart activity, the capacitive-coupled electrode is garmented with fabrics in the form of a chest band or a vest jacket. To compare the ECG data from the capacitive-coupled electrode with the conventional electrode(Ag-AgCl) system, the corelation coefficient between two signals is computed as 0.9517. Thus, we can conclude the fact that capacitive-coupled electrode system can measure a person's heart activity without any contact to his or her skin and can the interpreted as the ECG data.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.450-450
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• 2007

Indium tin oxide (ITO), which is used as an electrode in organic thin film transistors (OTFT), was modified with a self-assembled monolayer (SAM) by wet chemical surface modification. The surface of the ITO was treated by dipping method in a solution of 2-chloroethane phosphonic acid (2-CEPA) at room temperature. The work function in the ITO which was modified with the SAM in the 2-CEPA had 5.43eV. A surface energy and a transmittance were unchanged in an error range. On this study, therefore, possibility of ohmic contact is showed in the interface between the ITO and the organic semiconductors. These results suggest that the treatment of the ITO with the SAM can greatly enhance the performance of the OTFT.