• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.207-207
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• 2010

Both ZnO and GaN have excellent physical properties in optoelectronic devices such as blue light emitting diode (LED), blue laser diode (LD), and ultra-violet (UV) detector. The ZnO/GaN heterostructure, which has a potential to achieve the cost efficient LED technology, has been fabricated by using radio frequency (RF) sputtering, pyrolysis, metal organic chemical vapor deposition (MOCVD), direct current (DC) arc plasmatron, and pulsed laser deposition (PLD) methods. Among them, the PLD system has a benefit to control the composition ratio of the grown film from the mixture target. A 500-nm-thick ZnO film was grown by PLD technique on c-plane GaN/sapphire substrates. The post annealing process was executed at some varied temperature between from $300^{\circ}C$ to $900^{\circ}C$. The morphology and crystal structural properties obtained by using atomic force microscope (AFM) and x-ray diffraction (XRD) showed that the crystal quality of ZnO thin films can be improved as increasing the annealing temperature. We will discuss the post-treatment effect on film quality (uniformity and reliability) of ZnO/GaN heterostructures.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.55.1-55.1
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• 2010

차세대 디스플레이용 전극 재료는 투명하면서도 낮은 저항값을 가져야 하는 투명 전극 재료로 금속, 금속산화물, 전도성 고분자, 탄소재료 등을 들 수 있다. 금속재료는 전도도는 우수하지만, 낮은 투과도로 투명전극 재료로 적절하지 않고, 대표적인 금속산화물 재료인 indium tin oxide (ITO)의 경우, 우수한 투과성과 낮은 면저항을 기반으로 차세대 디스플레이용 전극으로 현재 사용되고 있다. 하지만 ITO 박막은 휘거나 접을 때 기계적 안정성이 취약한 문제점을 나타내고 있다. 이러한 문제점을 극복하기 위해 전도성과 탄성계수가 높고, 저온에서 대면적 공정이 가능한 CNT을 투명 박막 전극 연구가 활발히 진행되고 있다. 하지만 투명전극 제조시, 탄소 나노튜브 간의 van der waals 인력에 의한 응집 현상으로 인한 분산의 불안정성과 분산제 사용으로 인하여 탄소 나노튜브 박막전극의 전기적, 광학적 특성이 저하를 야기한다. 이에 본 실험에서는 아크 방전 공정으로 합성한 SWCNT 분산액을 사용하여 spray coating 방법으로 glass 위에 박막을 형성하였다. SWCNT 투명 박막 전극 위에 DC sputtering을 이용하여 얇은Ni를 도포한 후, $450{\sim}500^{\circ}C$, ethylene gas 분위기의 thermal CVD방법으로 Carbon NanoFibers (CNFs)를 생성시킴과 동시에 분산제를 burning out하였다. CNF 성장 전후의 투명 박막의 전기적 특성은 four point probe를 이용하여 면저항과 UV-vis 장비를 이용하여 가시광선 영역에서의 광학적 투과도를 측정 비교하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.97-100
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• 2001

This paper presents the characteristics of Ta-N thin-film strain gauges as high-temperature strain gauges, which were deposited on Si substrate by DC reactive magnetron sputtering in an argon-nitrogen atmosphere(Ar-(4~16%)$N_2$). These films were annealed for 1 hour in $2{\times}10^{-6}$ Torr vaccum furnace range $500\sim1000^{\circ}C$. The optimized conditions of Ta-N thin-film strain gauges were annealing condition($900^{\circ}C$, 1 hr.) in 8% $N_2$ gas flow ratio deposition atmosphere. Under optimum conditions, the Ta-N thin-films for strain gauges is obtained a high resistivity, $\rho=768.93$ ${\mu}{\Omega}cm$, a low temperature coefficient of resistance, TCR=-84 ppm/$^{\circ}C$ and a high temporal stability with a good longitudinal gauge factor, GF=4.12.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.63-66
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• 2002

Bi-layer Mo films were deposited on sodalime glass substrates using DC magnetron sputtering. As the gas pressure and power density, the resistivity varied from $1.5{\times}10^{-5}$ to $4.97{\times}10^{-4}{\Omega}{\cdot}cm$. Furthermore, stress direction yielded compressive-to-tensile transition stress curves. The microstructure of the compressive stress films which had poor adhesion consists of tightly packed columns, but of the tensile-stressed films had less dense structure. Under all gas pressure conditions, Mo films exhibited distinctly increasing optical reflection with decreasing gas pressure. The expansion of (110) peak width with the gas pressure meant the worse crystalline growth. Also, The highest efficiency was 15.2% on 0.2 $cm^2$. The fill factor, open circuit voltage and short circuit current were 63 %, 570 m V and 42.6 $mA/cm^2$ respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.3
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• pp.185-189
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• 2001

In this paper, since the research on the etching of SrBi$_2$Ta$_2$$O_{9}$(SBT) thin film was few (specially Cl$_2$-base) we had studied the surface reaction of SBT thin films. We have used the OES(optical emission spectroscopy) in high density plasma etching as a function of RF power, dc bias voltage, and Cl$_2$/(Cl$_2$+Ar) gas mixing ratio. It had been found that the etch rate of SBT thin films appeared to be more affected by the physical sputtering between Ar ions and surface of the SBT compared to the chemical reaction. The change of Cl radical density that was measured by the OES as a function of gas combination showed the change of the etch rate of SBT thin films. Therefore, the chemical reactions between Cl radical in plasma and components of the SBT enhanced to increase the etch rates SBT thin films. These results were confirmed by XPS(x-ray photoelectron spectroscopy) analysis.s.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.145-146
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• 2006

A fluorine-doped diamond-like carbon (F-DLC) stamp which has high contact angle, high UV-transmittance and sufficient hardness, was fabricated using the following direct etching method: F-DLC is deposited on a quartz substrate using DC and RF magnetron sputtering, PMMA is spin coated and patterned using e-beam lithography and finally, O2 plasma etching is performed to transfer the line patterns having 100 nm line width, 100 nm line space and 70 nm line depth on F-DLC. The optimum fluorine concentration was determined after performing several pre-experiments. The stamp was applied successfully to UV-NIL without being coated with an anti-adhesion layer.

• Journal of Korean Vacuum Science & Technology
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• v.1 no.1
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• pp.24-29
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• 1997

Surface morphologies and fundamental characteristics of molybdenum nitride films deposited by reactive dc magnetron sputtering were studied for application to Cu diffusion barrier. A phase transformation from Mo to $\gamma$-Mo$_2$N phase at 0.5$N_2$ flow ratio.($N_2$/(Ar+$N_2$)) equal to and larger than 0.2, whereas a second phase transformation to $\gamma$-MoN phase at 0.5 N2 flow ratio, With the variation of the N2 ratio the surface morphologies of the films were generally smooth except the cases of 0.2 and 0.3$N_2$ gas rations, where build-up of film stresses occurred. $\gamma$-Mo$_2$N film was found to crystallize at the deposition temperature of 40$0^{\circ}C$. The surfaces of $\gamma$-Mo$_2$N films deposited up to 40$0^{\circ}C$ were smooth, but the film deposited at 50$0^{\circ}C$ had very rough surface morphology. It seems that this was due to the building-up of thermal stresses at the high deposition temperature, which might lead to hillock formation.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.69-69
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• 2010

현대 건축물에서 건물에너지의 손실은 대부분은 창호를 통하여 유출되어지고 있으며 에너지 절감을 위해서는 창호의 단열성을 향상시켜야한다. 저방사(Low Emissivity) 코팅유리는 건축물의 냉난방비용을 절약할 수 있는 대표적인 건축재료로써 외부에서 유입되는 태양광의 가시광선 영역은 높은 투과율을 가지면서 적외선 영역과 겨울철 실내 난방열을 반사하는 특징을 지니는 박막코팅기술이다. 이 코팅유리는 일반적으로 유전체/금속/유전체 다층박막 구조로 되어있으며, 유전체층은 내구성 증진과 금속층의 반사를 낮추어 투과율이 향상된다. 금속층은 적외선영역의 복사에너지를 반사하는 역할을 하며 전도성이 우수한 Ag 또는 Au, Pt 등을 이용하고 있다. Ag의 경우 산화물기판 위에 증착하였을 경우 island 성장을 하고 이들의 합체는 전기적, 광학적 특성에 큰 영향을 미치게 된다. 본 연구에서는 DC-sputtering법으로 제조된 Ag/glass, Ag/Ta/glass 박막을 제조하고 Ta seeding이 Ag의 전기적, 광학적 성질에 미치는 영향을 관찰하였다. 박막의 표면 미세구조는 FE-SEM(Field Emission Scanning Electron Microscope)과 AFM(Atomic Force Microscope)으로, 표면저항은 4 point probe로 분석하였다. 광투과율은 UV-Vis spectroscopy와 FT-IR로 측정하였으며 측정파장범위는 각각 200~1100nm와 1400~2400nm 이다.

• Progress in Superconductivity
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• v.3 no.1
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• pp.49-55
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• 2001

Josephson junction arrays were fabricated by DC magnetron sputtering, self-aligning and reactive ion etching technique. The Al native oxide, formed by thermal oxidation, was used as the tunneling barrier of Nb/$Al-A1_2$$O_3$Nb trilayer. The arrays have 2,000 Josephson junctions with the area of $14\mu\textrm{m}$ $\times$ $46\mu\textrm{m}$. The gap voltages were in the range of 2.5 ~2.6 mV and the spread of critical current was $\pm$11~14%. When operated at 70~94 ㎓, the arrays generated zero-crossing steps up to 2.1~2.4 V. To improve transmission of microwave power and prevent diffusion of oxygen into Nb ground-plane while depositing $SiO_2$dielectric, we applied a plasma nitridation process to the Nb ground-plane. The microwave power was well propagated in Josephson junction arrays with nitridation. The difference in microwave transmission 7an be interpreted by the surface impedance change depending on nitridation.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.255-255
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• 2011

$SiO_2$는 유전체 물질로서 고온에 강하고 열 변화에 민감하지 않으며 자외선을 잘 투과시키는 특성 때문에 각종 광전자 소자에 많이 응용되고 있다. 최근에는 classical thermal oxidation 방식을 이용하여 태양전지의 효율을 증가하기 위한 표면 보호막, 유기발광다이오드의 보호막 및 barrier로 적용되고 있다. $SiO_2$ 박막의 경우 RF-DC sputtering, thermal evaporation, plasma enhanced chemical vapor deposition, E-beam evaporation 등의 다양한 방법을 통하여 제작되고 있다. 이들 중 E-beam evaporation 법은 높은 증착속도, 증착방향성, 낮은 불순물농도 등 많은 장점을 가지고 $SiO_2$ 박막 증착이 가증하다. 따라서 본 연구에서는 Si 기판위에 $SiO_2$를 증착각도를 0$^{\circ}$, 25$^{\circ}$, 50$^{\circ}$, 70$^{\circ}$로 변화시켜 증착하였고, 증착속도, 빔 세기, 기판 회전속도 등을 변화시켰다. 또한, 증착 각도에 따른 유전율 차이를 무반사 특성 향상에 응용하기 위해 다양한 layer 층을 순차적으로 성장시켰다. 제작된 $SiO_2$의 나노구조의 구조적, 광학적 특성은 field emission scanning microscopy, atomic force microscopy, UV-VIS-NIS spectrophotometer를 이용하여 분석되었다.