• Korean Journal of Materials Research
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• v.4 no.1
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• pp.31-36
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• 1994

The bonding behavior of $SiO_{2}$ thin film and glass during VCR head fabrication was investigated, varying the surface roughness of substrate and the sputtering parameter. Insufficient fillings of grooves In the $SiO_{2}$ film with glass was postulated to give rise to the generation of bubble in the glass. The surface roughness of $SiO_{2}$ film was found to depend on that of substrate. The lower the deposition rate, the smoother the surface of film. The bubble free glass after bonding could be obtained using substrate polished with 0.05$\mu\textrm{m}$ $Al_2O_3$ powder under the sputtering condition of 10% oxygen pressure.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.538-539
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• 2013

여러 장점으로 인해 OLED는 디스플레이 및 조명 등 적용분야가 넓어지고 있지만, 수분 및 산소에 취약하여 그 수명이 제한되는 단점이 있다. 이를 해결하고자 현재까지는 glass cap을 이용한 encapsulation 기술이 적용되고 있지만, flexible 기판에 적용하지 못하는 문제가 있다. 이러한 문제를 해결하고자 여러 가지 thin film encapsulation 기술이 적용되고 있으나 보다 신뢰성이 높은 기술의 개발이 절실한 때이다. Encapsulation 무기 박막 물질로서 $Si_3N_4$ 박막은 PE-CVD (Plasma Enhanced Chemical Vapor Deposition) 등의 박막 증착법을 사용한 많은 연구가 진행되어, 저온에서의 좋은 품질의 박막 증착이 가능하지만, 100도 이하의 thermal budget을 갖는 OLED Encapsulation에 사용하기에는 충분하지 않았다. CVD 박막의 특성을 더욱 개선하기 위해 최근 ALD (Atomic Layer Deposition) 방법을 통한 $Al_2O_3$ film 증착 방법이 연구되고 있지만, 낮은 증착 속도로 인해 양산에 걸림돌이 되고 있다. 본 연구에서는 또 다른 해결책으로서 Digital CVD 방법을 이용한 양질의 $Si_3N_4$ 박막의 증착을 연구하였다. 이것은 ALD 증착법과 유사하며, 1st step에서 PECVD 방법으로 4~5 ${\AA}$의 얇은 silicon 박막을 증착하고, 2nd step에서 nitrogen plasma를 이용하여 질화 반응을 진행하고, 이러한 cycle을 원하는 두께가 될 때까지 반복적으로 진행된다. 이 때 1 cycle 당 증착속도는 7 ${\AA}$/cycle 정도였다. 최적의 증착 방법과 조건으로 기존의 CVD $Si_3N_4$ 박막 대비 1/5 이하로 pinhole을 최소화 할 수는 있지만 완벽하게 제거하기는 힘든 문제가 있고, 이를 해결하기 위한 개선을 위한 접근 방법이 필요하다고 판단하였다. 본 연구에서는 무기물 박막인 carbon nitride를 이용한 SiN/C:N multilayer 증착 연구를 진행하였다. Fig. 1은 CVD 조건으로 증착된 두께 750 nm SiN film에서 여러 층의 C:N film layer를 삽입했을 때, 38 시간의 85%/$85^{\circ}C$ 가속실험에 따라 OLED의 발광 사진이다. 그림에서 볼 수 있듯이 C:N 층을 삽입하고 또한 그 박막의 수가 증가함에 따라서 OLED에 대한 encapsulation 특성이 크게 개선됨을 확인할 수 있다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.71-74
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• 1996

Ta$_2$O$_{5}$ film ale recognized as promising capacitor dielectric for future DRAM\`s. The electrical properties of Ta$_2$O$_{5}$films greatly depend on the heating condition. In the practical fabrication process, several annealing process, such as the annealing of Al in H$_2$(about 40$0^{\circ}C$) and reflow of BPSG (borophosphosilicate glass) film in $N_2$(about 80$0^{\circ}C$), exist after deposition of Ta$_2$O$_{5}$ film. In this paper, we describe the temperature effect on the electrical properties of W/Ta$_2$O$_{5}$/Si structure. The thin film of Ta$_2$O$_{5}$ and tungsten have been deposited on p-si(100) wafer using the sputtering system. The heating temperature was varied from 500 to 90$0^{\circ}C$ in $N_2$for 30min and The degree of temperature is 100\`C. In a log(J/E$^2$) Vs 1/E plot of typical I-V data, we find a linear relationship for the temperature of 500, $600^{\circ}C$ and as deposition. This could indicate Fowler-Nordheim tunneling as the dominant mode of current transports. However, we can not find a linear relationship for the temperature above $700^{\circ}C$. This could not indicate Fowler-Nordheim tunneling as the dominant mode of current transport. The high frequency (1MHz) capacitance-voltage (C-V) of W/Ta$_2$O$_{5}$/Si Capacitor were investigated on the basis of shift in the threshold voltage and dielectric constant. The magnitude of the threshold voltage and dielectric constant depends on the heating temperature, and increases with heating temperature.temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.111-114
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• 1999

Electroluminescence(EL) devices based on organic thin films have been attracted lots of interests in large-area light-emitting display. In this stuffy, an emissive layer was fabricated using Langmuir-Blodgett(LB) technique in organic light-emitting (OLEDs). This emissive organic material was synthesized and named PECCP[poly(3.6-N-2-ethylhexyl carbazolyl cyanoterephthalidene)] which has a strong electron donor group and an electron acceptor group in main chain repeated unit. This material has good solubility in common organic solvents such as chloroform. THF, etc, and has a good stability in air. The Langmuir-Blodgett(LB) technique has the advantage of precise control of the thickness down to the molecular scale, In particular, by varying the film thickness it is possible to investigate the metal/polymer interface. Optimum conditions for the LB film deposition are usually determined by investigating a relationship between a surface pressure $\pi$ and an effective are A occupied by one molecule on the subphase. The LB films were deposited on an indium-tin-oxide(ITO) glass at a surface pressure of 10 mN/m and dipping speed of 12 mm/min after spreading PECCP solution on distilled water surphase at room temperature, Cell structure was ITO/PECCP LB film/Alq$_3$/Al. We considered PECCP as a hole -transport layer inserted between the emissive layer and ITO. We also used Alq$_3$ as an emissive layer and an electron transport layer. We measured current-voltage(I-V) characteristics, UV/visible absorption, PL spectrum and EL spectrum of the OLEDs.

• Korean Journal of Materials Research
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• v.14 no.12
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• pp.876-884
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• 2004

This study was to investigate whether the bioactivity of the anodized and hydrothermally treated Ti-6Al-7Nb alloy were affected by the time of hydrothermal treatment. Anodizing was performed at current density 30 $mA/cm^2$ up to 300 V in electrolyte solutions containing $DL-{\alpha}-glycerophosphate$ disodium salt hydrate $(DL-{\alpha}-GP)$ and calcium acetate (CA). Hydrothermal treatment was done at $300^{\circ}C$ for 30 min, 1 hr, 2 hrs, and 4 hrs to produce a thin film layer of hydroxyapatite (HA). The bioactivity was evaluated from HA formation on the surfaces in a Hanks' solution with pH 7.4 at $36.5^{\circ}C$ for 10, 20, and 30 days. Anodic oxide films were porous with pore size of $1\sim4{\mu}m\;and\;3\sim4{\mu}m$ thickness. The anodic oxide films composed with strong anatase peak with presence of rutile peak, and showed the increase in intensity of anatase peak after hydrothermal treatment. It was shown that the intensity of anatase peak increased with increasing the time of hydrothermal treatment but was no difference in rutile peak. The corrosion voltage was the highest in the group of hydrothermal treatment for 2 hrs (Ecorr: -338.6 mV). The bioactivity in Hank's solution was accelerated with increasing the time of hydrothermal treatment.

• Journal of Electrochemical Science and Technology
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• v.13 no.2
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• pp.213-226
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• 2022

In the present study, the corrosion behavior of aluminum Al-7075 tempered (T-6 condition) alloy was evaluated by immersion testing and electrochemical testing in 1.75% and 3.5% NaCl environment at acidic, neutral and basic pH. The data obtained by both immersion tests and electrochemical corrosion tests (potentiodynamic polarization and electrochemical impedance spectroscopy tests) present that the corrosion rate of the alloy specimens is minimum for the pH=7 condition of the solution due to the formation of dense and well adherent thin protective oxide layer. Whereas the solutions with acidic and alkaline pH cause shift in the corrosion behavior of aluminum alloy to more active domains aggravated by the constant flux of acidic and alkaline ions (Cl^- and OH^-) in the media which anodically dissolve the Al matrix in comparison to precipitated intermetallic phases (cathodic in nature) formed due to T6 treatment. Consequently, the pitting behavior of the alloy, as observed by cyclic polarization tests, shifts to more active regions when pH of the solutions changes from neutral to alkaline environment due to localized dissolution of the matrix in alkaline environment that ingress by diffusion through the pores in the oxide film. Microscopic analysis also strengthens the results obtained by immersion corrosion testing and electrochemical corrosion testing as the study examines the corrosion behavior of this alloy under a systematic evaluation in marine environment.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1245-1247
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• 1995

In this paper, Analyzed structual property using SEM and XRD. The longer distance between substrate and target enhance crystalographic orientation of (110)plane, but inhibit growth of (002)plane. Also, deposited ZnO thin film on electrode layer inhibit crystalographic orientation of (002)plane, expecially Al electrode inhibit stronger than Pt layer. And using fabricated transducer, analyzed eletric and frequency characteristics.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.159-162
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• 2002

The eleventh-order coupled line lowpass filter(LPF) was designed to suppress harmonics and spurious signals. The microstrip type LPF was fabricated using a high-$T_{c}$ superconductor(HTS) $YBa_{2}$$Cu_{3}$$O_{7-x}$(YBCO) thin film with the $CeO_{2}$ buffer layer which was deposited on the sapphire ($Al_{2}O_{3}$) substrate of 30 x 30 $mm^{2}$. The coupled-line type LPF was designed for 1.2 GHz of cutoff frequency with 0.01 dB of ripple level at passband. The fabricated HTS LPF shows excellent attenuation characteristics in stopband of 1.2~9.5GHz (7-attenuation poles in the stopband), and shows low insertion loss (0.2 dB) and return loss (17.1 dB) in the pass- band. These measured results match well with those obtained by the EM simulation. This clearly demonstrates that the HTS LPF can suppress harmonics and spurious signals effectively.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.31-34
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• 1998

CDMA base station SAW filter has been designed and fabricated successfully. Through the computer simulation, SAW filter is designed to have center frequency of 69.99MHz, ripples lower than 0.7dB and rejection level lower than 50dB. To obtain low noise band pass SAW filter, Input electrode has a apodization type and output electrode has a withdrawal type. For the fabrication of the SAW filter, Al thin film is deposited to the quartz substrates. The fabricated SAW filter has center frequency of 70.5MHz, ripples of 1dB and rejection level of 45dB.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.43.1-43.1
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• 2011

Hydrogenated amorphous Si (a-Si:H), low temperature poly Si (LTPS) 등 기존 thin film transistors (TFTs)에 사용되던 채널 물질을 대체할 재료로써 다양한 연구가 진행되고 있는 amorphous indium-gallium-zinc-oxide (a-IGZO)는 TFT에 적용하였을 때 뛰어난 전기적 특성과 재연성을 나타낼 뿐만 아니라 넓은 밴드갭을 가져 투명소자로도 응용이 가능하다. 본 연구에서는 a-IGZO의 열처리에 따른 소자의 전기적 특성과 조성 분포의 관계를 확인하기 위해 다음과 같이 실험을 진행하였다. Si/SiO2 기판 위에 DC sputter를 이용하여 IGZO를 증착하고 $350^{\circ}C$에서 열처리를 한 후 evaporator로 Al 전극을 형성시켰다. 이 때 전기적 특성의 변화를 비교하기 위해 열처리 한 샘플과 열처리 하지 않은 샘플에 대해 I-V 특성을 측정하였고, 채널 내부의 조성 분포 변화를 transmission electron microscopy (TEM)의 energy dispersive spectrometer (EDS)를 이용하여 관찰하였다. 그 결과 열처리 된 a-IGZO 채널 층의 산소 비율이 감소하였으며 전체적인 조성이 고르게 분포 되었고 전기적 특성은 향상되었다.