• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.06a
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• pp.496-497
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• 2009

This paper describes about the realization of a remote RF sensor system and its applications. RF Sensor System was designed and realized on DSP over the range of high frequency such as about 200[KHz]. It should be "wireless", "implantable" and "batteryless". Futhermore, the system should be consist of passive components such as R, Land C. The measurement was given using the inductive coupling principle between primary source part and secondary sensor part. This newly developed parameter estimation system can be easily applied to the Ambient Intelligent System including the ubiquitous computing and the sensitive environmental changes.

• Journal of Ceramic Processing Research
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• v.13 no.spc2
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• pp.260-264
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• 2012

We have investigated the effect of ambient gases on the structural, electrical, and optical characteristics of IZO thin films intended for use as anode contacts in the organic light emitting diodes (OLED) devices. These IZO thin films were deposited on the PES film by radio frequency (RF) magnetron sputtering under different ambient gases (Ar, Ar + O2, and Ar + H2) at room temperature. In order to investigate the influences of the ambient gases, the flow rate of oxygen and hydrogen in argon has been changed from 0.1 sccm to 0.5 sccm, respectively. All the IZO thin film has an (222) preferential orientation regardless of ambient gases. The electrical resistivity of the IZO film increased with increasing O2 flow rate, whereas the electrical resistivity decreased sharply under an Ar + H2 atmosphere and was nearly similar regardless of the H2 flow rate. The change of electrical resistivity with changes in the ambient gas composition was mainly interpreted in terms of the charge carrier concentration rather than the charge carrier mobility. All the films showed the average transmittance over 85% in the visible range. The OLED device was fabricated with different IZO substrates made with the configuration of IZO/α-NPD/DPVB/Alq3/LiF/Al in order to elucidate the performance of the IZO substrate. The current density and the luminance of OLED devices with IZO thin films deposited in 0.5 sccm H2 ambient gas are the highest amongst all other films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.12
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• pp.1134-1139
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• 2006

Electrical, optical, and structural properties of indium zinc oxide (IZO) anode films grown by a RF magnetron sputtering were investigated as functions of RF power and working pressure in pure Ar ambient. To investigate electrical, optical and structural properties of IZO anode films, 4-point probe and UV/VIS spectrometry, and X-ray diffraction (XRD) were performed, respectively. A sheet resistance of $15.2{\Omega}/{\square}$, average transmittance above 80 % in visible range, expecially above 85 % in 550 nm, and root mean square roughness of 1.13 nm were obtained from optimized IZO anode films grown in oxygen free ambient. All samples show amorphous structure regardless of RF power and working pressure due to low substrate temperature. In addition, XPS depth profile obtained from IZO/PES exhibits that there is no obvious evidence of interfacial reaction between IZO and PES substrate. Furthermore, current-voltage-luminance of the flexible phosphorescent flexible OLEDs fabricated on IZO anode shows dependence on sheet resistance of the IZO anode. These results indicate that the IZO anode is a promising candidate to substitute conventional ITO anode for high-quality flexible displays.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.4
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• pp.7-12
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• 2019

Ambient backscatter communication is limited to channel estimation technique through a pilot signal, which is a channel estimation method in current RF communication, due to transmission power efficiency. In a limited transmission power environment, the research of traditional ambient backscatter communication has been studied assuming that it is an ideal channel without signal distortions due to channel conditions. In this paper, we propose an expectation-maximization(EM) algorithm, one of the blind channel estimation techniques, as a channel estimation method in ambient backscatter communication system which is the state of channel following normal distribution. In the proposed system model, the simulations confirm that channel estimate through EM algorithm is approaching the lower bound of the mean square error compared with the Bayesian Cramer-Rao Boundary(BCRB) to check performance. It shows that the channel parameter can be estimated in the ambient backscatter communication system.

• Korean Journal of Materials Research
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• v.13 no.10
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• pp.640-644
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• 2003

NiCr thin films were fabricated by rf magnetron sputtering for applying to both the top electrode and absorption layer on Pb(Zr, Ti)O$_3$(PZT) thin films for infrared sensors. The rms roughness and resistivity of NiCr films prepared with Ni power of 80 W and Cr power of 50 W showed the most stable oxidation resistance after annealing at $600^{\circ}C$ for 5 min in oxygen ambient. The rms roughness and resistivity of NiCr films annealed at $V^{\circ}C$ in oxygen ambient were about 2$0\AA$ and $70 \mu$Ω-cm, respectively. As-deposited Ni/PZT/Pt and NiCr (Ni 80 W, Cr 50 W)/PZT/Pt structures showed well saturated hysteresis loops. However, in case of the samples annealed at $500^{\circ}C$ in oxygen ambient, only NiCr/PZT/Pt showed saturated loops having a remanent polarization of 20$\mu$C/$\textrm{cm}^2$. Ultra-thin NiCr films showed a possibility as a top electrode for infrared sensors.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.4
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• pp.318-322
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• 2009

In this paper, to establish growth technology of ZnO:Al thin films at low temperature applied to photoelectronic devices, ZnO:Al were prepared by RF magnetron sputtering on glass substrate at room temperature using different RF power with subsequent annealing process at different temperature in $H_2$ ambient. The resistivity of hydrogen-annealed ZnO:Al thin film at temperature of $300^{\circ}C$ was reduced to $8.32{\times}10^{-4}{\Omega}cm$ from $9.44{\times}10^{-4}{\Omega}cm$ which was optimal value for as-grown films. X-ray photoelectron spectroscopy(XPS) revealed that improved electrical properties are ascribed to desorption of the negatively charged oxygen species from the grain boundary surfaces by the hydrogen annealing process.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11A
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• pp.1091-1096
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• 2010

Stiction in microelectromechanical systems (MEMS) has been a major failure mechanism. Especially, in RF MEMS switches, moving parts often suffered in-use and release related stiction problems. Some materials and methods have been used to prevent this problem. Diamond-like carbon (DLC) has not only been used as a protective material owing to its good mechanical properties but also has been used as a hydrophobic material. Its properties could be controlled by post annealing treatment in various conditions. We synthesized DLC films using a radio frequency plasma enhanced chemical vapor deposition (RF PECVD) method on silicon substrates using methane ($CH_4$) and hydrogen ($H_2$) gas. Then, the change of the hydrophobic property of the films was investigated undervarious annealing temperatures in nitrogen and in oxygen ambient. The films, that were annealed above $700^{\circ}C$ in nitrogen ambient, showed a high contact angle of water (> $90^{\circ}$) even though their mechanical property was sacrificed to some degree. The structural variation and the changes of the hydrophobic and mechanical properties of the DLC films were analyzed by Raman spectrum, contact angle measurement, surface profiler, and a nanoindentation test.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.6-10
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• 2015

RF energy harvesting technology is a promising technology for generating the electrical power from ambient RF signal to operate low-power consumption devices(eg. sensor) in wireless communication networks. This paper, motivated by this and building upon existing CR(Cognitive Radio) network model, proposes a optimal control policy for RF energy harvesting CR networks model where secondary users that have low power consumption harvest ambient RF energy from transmission by nearby active primary users, while periodically sensing and opportunistically accessing the licensed spectrum to the primary user's network. We consider that primary users and secondary users are distributed as Poisson point processes and contact with their intended receivers at fixed distances. Finally we can derive the optimal frame duration, transmission power and density of secondary user from the proposed model that can maximize the secondary users's throughput under the given several conditions and suggest future directions of research.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.755-758
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• 2000

YMnO$_3$films have been deposited with different Rf powers of 60W, 80W, 100W, and 120W. The structural properties of YMnO$_3$films on Si(100) were analysed by XRD(X-ray diffraction). The c-axis oriented peaks of YMnO$_3$were observed deposited in YMnO$_3$/Si(100) structure of RF power at 87$0^{\circ}C$ in oxygen ambient, and the peaks were enlarged by increasing The RF powers. The dielectric constant of the film deposited at 100W and 120W of RF power were about 19, 20 respectively.

• Journal of the Semiconductor & Display Technology
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• v.8 no.1
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• pp.33-38
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• 2009

We have investigated the effect of the ambient gases on the characteristics of AZO thin films for the OLED (organic light emitting diodes) devices. These AZO thin films are deposited by rf-magnetron sputtering under different ambient gases (Ar, Ar+$O_2$, and Ar+$H_2$) at 300. In order to investigate the influences of the oxygen and hydrogen, the flow rate of oxygen and hydrogen in argon mixing gas has been changed from 0.2sccm to 1sccm and from 0.5sccm to 5sccm, respectively. The AZO thin films were preferred oriented to (002) direction regardless of ambient gases. The electrical resistivity of AZO film increased with increasing flow rate of $O_2$ under Ar+$O_2$ while under Ar+$H_2$ atmosphere the electrical resistivity showed minimum value near 1sccm of $H_2$. All the films showed the average transmittance over 80% in the visible range. The OLED device was fabricated with different AZO substrates made by configuration of AZO/$\acute{a}$-NPD/DPVB/$Alq_3$/LiF/Al to elucidate the performance of AZO substrate.