• Journal of the Korean Society for Heat Treatment
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• v.24 no.6
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• pp.338-342
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• 2011

Ga doped ZnO (GZO) thin films were deposited with RF magnetron sputtering on glass substrate and then the effect of post deposition annealing at nitrogen atmosphere on the structural, optical and electrical properties of the films was investigated. The post deposition annealing process was conducted for 30 minutes at different temperature of 150, 300 and $450^{\circ}C$, respectively. As increase annealing temperature, GZO films show the increment of the prefer orientation of ZnO (002) diffraction peak in the XRD pattern and the optical transmittance in a visible wave region was also increased, while the electrical sheet resistance was decreased. The figure of merit obtained in this study means that GZO films which vacuum annealed at $450^{\circ}C$ have the highest optoelectrical performance in this study.

• Journal of the Korean Society for Heat Treatment
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• v.30 no.1
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• pp.13-16
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• 2017

$SnO_2$ single layer films and 2 nm thick Ni thin film intermediated $AZO/Ni/SnO_2$ trilayer films were deposited on glass substrate at room temperatures by RF and DC magnetron sputtering and then the optical and electrical properties of the films were investigated to enhance opto-electrical performance of $SnO_2$ single layer films. As deposited $SnO_2$ films show the optical transmittance of 81.8% in the visible wavelength region and a resistivity of $1.2{\times}10^{-2}{\Omega}cm$, while $AZO/Ni/SnO_2$ films show a lower resistivity of $5.8{\times}10^{-3}{\Omega}cm$ and an optical transmittance of 77.1% in this study. Since $AZO/Ni/SnO_2$ films show the higher figure of merit than that of the $SnO_2$ single layer films, it is supposed that the $AZO/Ni/SnO_2$ films can assure high opto-electrical performance for use as a transparent conducting oxide in various display applications.

• Journal of the Korean Society for Heat Treatment
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• v.31 no.4
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• pp.187-193
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• 2018

In this study, the electrical conductivity, transmittance and gas barrier properties of diamond-like carbon (DLC) thin films were studied. DLC is an insulator, and has transmittance and oxygen gas barrier properties varying depending on the thickness of the thin film. Recently, many researchers have been trying to apply DLC properties to specific industrial conditions. The DLC thin films were deposited by PECVD (Plasma Enhanced Chemical Vapor Deposition) process. The doping gas was used for the DLC film to have electrical conductivity, and the optimum conditions of transmittance and gas barrier properties were established by adjusting the gas ratio and DLC thickness. In order to improve the electrical conductivity of the DLC thin film, $N_2$ doping gas was used for $CH_4$ or $C_2H_2$ gas. Then, a heat treatment process was performed for 30 minutes in a box furnace set at $200^{\circ}C$. The lowest sheet resistance value of the DLC film was found to be $18.11k{\Omega}/cm^2$. On the other hand, the maximum transmittance of the DLC film deposited on the PET substrate was 98.8%, and the minimum oxygen transmission rate (OTR) of the DLC film of $C_2H_2$ gas was 0.83.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.2
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• pp.352-359
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• 2008

RTLS(Real Time Location Systems) is a technology that identifies a location of a target object and provides peat visibility at a work place. Unlike those of the overseas, domestic ports and shipyards have narrow work places and thus, the efficient utilization of these spaces is one of the most important considerations for improving productivity. Companies considering implementation of RTLS should understand its limitations or applicability. In this paper, problems of RTLS such as fading factors which were caused from the features of RF, and limitations caused from the preconditions of RTLS were explained. To overcome those problems, three types of solutions such as movable RTLS, semi-movable RTLS and combined RTLS with other technologies were suggested.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.517-520
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• 2009

Healthcare application system has been actively researched to apply WSN technology to healthcare area with a mobile sensor node of low cost, low power, and small size. Sensor node has the problem for transmission range of RF power and time delay of the wireless routing connectivity between sensor nodes. In this paper, we proposes a new method utilizing mobile sensor nodes with relay sensor nodes for quick network routing changing using query technique in healthcare system. A query processor to control and manage the routing changing of sensor nodes in a wireless sensor network was designed and implemented. The user's PC transmits the beacon message which will change the quick link routing according to activity status of patient in wireless sensor network. We describe the implementation for query protocol that is very effective of power saving between sensor nodes.

• Journal of the Korean institute of surface engineering
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• v.54 no.6
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• pp.302-306
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• 2021

SnO₂ 30/Ag 15/SnO₂ 30 nm(SAS) tri-layer films were deposited on the glass substrates with RF and DC magnetron sputtering and then electron beam is irradiated on the surface to investigate the effect of electron bombardment on the opto-electrical performance of the films. electron beam irradiated tri-layer films at 1000 eV show a higher figure of merit of 2.72×10^-3 Ω^-1 than the as deposited films due to a high visible light transmittance of 72.1% and a low sheet resistance of 14.0 Ω/☐, respectively. From the observed results, it is concluded that the post-deposition electron irradiated SnO₂ 30/Ag 15/SnO₂ 30 nm tri-layer films can be used as a substitute for conventional transparent conducting oxide films in various opto-electrical applications.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.3
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• pp.141-147
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• 2019

In this paper, a beam pattern performance analysis was performed according to number of array elements and spacing of the phase array antenna. The distance between array elements in an array structure design was reduced due to the electrical length of Ka-band, which increases the number of array elements in applying the aperture. If the number of elements reduce by widening the array distance, the grating lobes of the same size as the main beam will occur in visible region. If the number of array elements should be applied to a system where the number of array elements should be minimized, the analysis was performed on a plan to reduce the number of array elements and minimize degradation of performance, such as beam width and side lobe level.

• Journal of IKEEE
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• v.22 no.4
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• pp.1068-1072
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• 2018

In underwater communications, there are many challenges due to energy limitations, long propagation delay, low data rate, and high power loss, unlike terrestrial RF communications. Especially, the propagation delay of underwater acoustic channel is five orders of magnitude higher than in electro-magnetic terrestrial channels due to the low speed of sound(1,500m/s). Thus, the MAC protocols for terrestrial communications are not suitable for underwater network. In this paper, we studied the considerations for MAC protocol in underwater acoustic channel. Here, we concentrated on CSMA based MAC protocols. From the results, we confirmed that the number of control packets has an important effect on the performance in underwater environment. These results would be useful in designing MAC protocols for underwater acoustic communications.

• Journal of the Semiconductor & Display Technology
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• v.17 no.4
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• pp.66-69
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• 2018

This study was researched the electrical properties of semiconductor devices such as ITO, $SiO_2$, $V_2O_5$ thin films. The films of ITO, $SiO_2$, $V_2O_5$ were deposited by the rf magnetron sputtering system with mixed gases of oxygen and argon to generate the plasma. All samples were cleaned before deposition and prepared the metal electrodes to research the current-voltage properties. The electrical characteristics of semiconductors depends on the interface's properties at the junction. There are two kinds of junctions such as ohmic and schottky contacts in the semiconductors. In this study, the ITO thin film was shown the ohmic contact properties as the linear current-voltage curves, and the electrical characteristics of $SiO_2$ and $V_2O_5$ films were shown the non-linear current-voltage curves as the schottky contacts. It was confirmed that the electronic system with schottky contacts enhanced the electronic flow owing to the increment of efficiency and increased the conductivity. The schottky contact was only defined special characteristics at the semiconductor and the interface depletion layer at the junction made the schottky contact which has the effect of leakage current cutoff. Consequently the semiconductor device with shottky contact increased the electronic current flow, in spite of depletion of carriers.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.5
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• pp.376-381
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• 2019

In this work, we evaluated the structural, electrical and optical properties of $Ge_8Sb_2Te_{11}$ and Cu-doped $Ge_8Sb_2Te_{11}$ thin films prepared by rf-magnetron reactive sputtering. The 200-nm-thick deposited films were annealed in a range of $100{\sim}400^{\circ}C$ using a furnace in an $N_2$ atmosphere. The amorphous-to-crystalline phase changes of the thin films were investigated by X-ray diffraction (XRD), UV-Vis-IR spectrophotometry, a 4-point probe, and a source meter. A one-step phase transformation from amorphous to face-centered-cubic (fcc) and an increase of the crystallization temperature ($T_c$) was observed in the Cu-doped film, which indicates an enhanced thermal stability in the amorphous state. The difference in the optical energy band gap ($E_{op}$) between the amorphous and crystalline phases was relatively large, approximately 0.38~0.41 eV, which is beneficial for reducing the noise in the memory devices. The sheet resistance($R_s$) of the amorphous phase in the Cu-doped film was about 1.5 orders larger than that in undoped film. A large $R_s$ in the amorphous phase will reduce the programming current in the memory device. An increase of threshold voltage ($V_{th}$) was seen in the Cu-doped film, which implied a high thermal efficiency. This suggests that the Cu-doped $Ge_8Sb_2Te_{11}$ thin film is a good candidate for PRAM.