• Journal of IKEEE
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• v.18 no.4
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• pp.620-624
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• 2014

In this study, the electrical characteristics of Ni/CNT/$SiO_2$ structures were investigated in order to analyze the mechanism of carbon nanotubes in 4H-SiC MIS device structures. We fabricated 4H-SiC MIS capacitors with or without carbon nanotubes. Carbon nanotubes were dispersed by isopropyl alcohol. The capacitance-voltage (C-V) is characterized at 300 to 500K. The experimental flat-band voltage ($V_{FB}$) shift was positive. Near-interface trapped charge density and oxide trapped charge density values of Ni/CNT/$SiO_2$ structure were less than values of reference samples. With increasing temperature, the flat-band voltage was negative. It has been found that its oxide quality is related to charge carriers or defect states in the interface of 4H-SiC MIS capacitors. Gate characteristics of 4H-SiC MIS capacitors can be controlled by carbon nanotubes between Ni and $SiO_2$.

• Korean Journal of Materials Research
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• v.4 no.2
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• pp.136-142
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• 1994

Epitaxial TiSiz films have been grown by UHV deposition of Ti on atomically clean Si(ll1)- orientated substrates. The Ti film of 50$\AA$ was deposited on the reconstructed Si(ll1) surface at room temperature. The sample was annealed up to $800^{\circ}C$ in $100^{\circ}C$ increments. The structure of the TiSiL films have been identified as the C49 metastable phase by electron diffraction patterns. Scanning electron microscopy( SEM) shows three different types of Tiksilicide island morphologies. The individual island structures are single crystal and are considered to be epitaxy with different crystallographic orientations. The orientational relationships of the $TiSi_{2}$ islands is given by [ 172 1 C49 $TiSi_{2}$//[110] Si and (021) C49 $TiSi_{2}$// (111)Si.

• Composites Research
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• v.23 no.2
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• pp.10-16
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• 2010

$Al_2O_3$ fiber and SiC particle hybrid metal matrix composites (MMCs) were manufactured by squeeze casting method investigated for their tribological properties. The pin specimens had different ratios of fiber to particle content but their total weight fraction was constant at 20 wt. %. Tribological tests were performed with a pin-on-disk friction and wear tester. The investigation of the dry tribological characteristics of hybrid MMCs were carried out at room temperature and elevated temperature of$100^{\circ}C$ and$150^{\circ}C$. The morphologies of worn surfaces were examined by scanning electron microscope (SEM) to observe tribological characteristics and investigate wear behavior. The results revealed that the wear resistance improved with the content of SiCp increased of the planar random (PR) MMCs at room temperature. At the elevated temperature, it revealed that the wear resistance of normal (N) MMCs was superior to that of the PR-MMCs due to PR-fibers were easily pulled out holistically from the worn surface. Meanwhile, the coefficient of friction decreased with the temperature increasing.

• Journal of the Korean Ceramic Society
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• v.34 no.3
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• pp.296-302
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• 1997

The effect of cold cyclic compaction on densification of SiC whisker/Al2O3 composite was investigated. Re-lative density of the compact increased as the number of cycle and the compaction pressure increased and the bias pressure decreased. The rate of loading and unloading and the frequency of cold cyclic compaction did not affect much on sliding and rearrangement of the particles. Fracture of SiC whisker was hardly ob-served during cold cyclic compaction and the direction of whisker was randomly oriented throughout the compact regardless of the direction of compaction. Thus, cold cyclic compaction may be an efficient method to densify SiC whisker/Al2O3 composite.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.282.1-282.1
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• 2014

산소 플라즈마 전처리가 ZnO/Si 박막 및 계면에 미치는 영향과 그것이 n-ZnO/p-Si 이종접합 다이오드의 전기적 특성에 관여하는 상관관계 등을 조사하였다. ZnO 박막을 Si 기판 위에 Sputter법으로 증착하였으며, 양질의 n-ZnO/p-Si 다이오드를 제작하기 위하여 산소 플라즈마를 이용하여 Si 기판의 표면을 전처리하는 기법을 선택하였다. 산소 플라즈마에 의해 전처리된 시편의 경우, (002) ZnO 보다 (101) ZnO가 더 우세하게 성장되었으며, (101) ZnO의 완화된 c-축 배향성 때문에 수평방향으로의 박막 성장이 이루어졌고, 그로 인해 ZnO 박막의 결정립 크기가 상대적으로 증가하는 것이 관측되었다. 이처럼 (101) 방향으로 성장된 ZnO 박막의 경우, 산소결공 등의 자생결함 밀도가 상대적으로 높아져 결국 캐리어 농도의 증가를 야기시켰다. 이러한 산소 플라즈마 전처리 효과는 n-ZnO/p-Si 이종접합 다이오드의 전도 특성과 밀접한 관련이 있으며, 특히 다이오드의 전도 특성을 현저히 개선시키는 것으로 관측되었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.298-299
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• 2011

최근 입력소자로 활용되는 터치스크린은 키보드나 마우스와 같은 입력장치를 사용하지 않고, 스크린에 손가락, 펜 등을 접촉하여 입력하는 방식이다. 터치패널의 구현방식에 따라 저항막(Resistive) 방식, 정전용량(Capacitive) 방식, SAW (Surface Accoustic Wave; 초음파) 방식, IR (Infrared; 적외선) 방식등으로 구분된다. 특히 최근 관심을 받고 있는 IR 방식은 적외선이 사람의 눈에는 보이지 않으나, 직진성을 가지고 있어 장애물이 있으면 차단되는 특성을 이용한 방식이다. IR방식의 터치패널은 발광(Light emitting)소자와 수광(Light detecting)소자가 마주하도록 배치되어 터치에 의해 차단된 좌표를 인식하게 되며, ITO 필름 등이 필요 없어 Glass 1장으로도 구현이 가능하며 투과율이 우수하다. 이러한 IR 방식의 터치패널을 제작하기 위하여 사용된 IR 광검출기는 광학적 band-gap이 작은 박막물질을 필요로 한다. 본 연구에서는 IR 광검출을 위한 물질로 SiGe를 co-sputtering 기법을 이용하여 성장시켰다. 일반적으로 SiGe 박막을 성장시키기 위하여 저압화학기상증착법(low pressure chemical vapor deposition, LPCVD)이나 고진공 LPCVD를 사용하지만 본 연구에서는 CVD에 비하여 무독성이면서 환경친화적이고 초기투자비용이 낮은 증착장비인 sputtering을 이용하였다. 본 연구에서 성장된 SiGe 박막은 400$^{\circ}C$에서 rf plasma가 인가된 Ge과 dc plasma가 인가된 Si의 power를 조절하여 결정화도가 70% (Fig. 1)이고 결정성장방향이 (111)과 (220)방향으로 성장하는 SiGe 박막을 얻을 수 있었다. 본 논문에서는 co-sputtering 성장조건에 따라 성장된 SiGe의 박막 특성을 논의할 것이다.

• Journal of the Korean Ceramic Society
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• v.36 no.1
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• pp.43-49
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• 1999

Gas pressure sintered silicon nitride based composites with 0~5wt% $\beta$-Si3N4 whiskers were prepared. The whiskers were unidirectionally oriented by a modified tape casting technqiue and green bodies with various microstructure were formed by changing stacking sequences of sheets cut from the tape. Orientations of the large elongated grains of the sample after gas pressure sintering were the same as the those of the whiskers of green body, and the sintering shrinkage and mechanical properties of sintered sample were consistent with the microstructural characteristics. In case of unidirectional samples, the sintering shrinkage normal to whisker alignment direction was larger than that parallel to the direction. The shrinkage difference inceaed as the whiskercontent increaed. As whisker content increaed, the crack length normal to and parallel to tape casting direction became shorter and larger, respectively. Although the grain size increased by th whisker addition, the flexural strength of unidirectional samples was not lower than that of smaple without the whisker. In case of crossplied and 45$^{\circ}$rotated samples, the anisotropy of mechanical preoperties disappeared.

• Journal of the Korean Vacuum Society
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• v.10 no.1
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• pp.22-26
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• 2001

Microstructures of AlN thin films on Si substrates grown by plasma assisted molecular beam epitaxy were analyzed with various growth temperatures and substrate orientations. Reflection high energy electron diffraction (RHEED) patterns were checked for the in-situ monitoring of the growth condition. X-ray diffraction(XRD), double crystal X-ray diffraction (DCXD), and transmission electron microscopy/diffraction (TEM/TED) techniques were employed to characterize the microstructure of the films after growth. On Si(100) sub-strates, AlN thin films were grown mostly along the hexagonal c-axis orientation at temperature higher than $850^{\circ}C$. On the other hand the AlN films on Si(111) were epitaxially grown with directional coherencies in AlN(0001)/Si(111), AlN(1100)/Si(110), and AlN(1120)/Si(112). The microstructure of AlN thin films on Si(111) substrates, with a full width at half maximum of almost 3000 arcsec at 2$\theta$=$36.2^{\circ}$, showed that the single crystal films were grown, even if they includ a lot of crystal defects such as dislocations and stacking faults.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.67-67
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• 2000

CeO2는 cubic 구조의 일종인 CaR2 구조를 가지고 있으며 격자상수가 Si의 격장상수와 매우 비슷하여 Si 기판위에 에피텍셜하게 성장할 수 있는 가능성이 매우 크다. 따라서 SOI(silicon-on-insulator)구조의 실현을 위하여 Si 기판위에 CeO2 박막을 에피텍셜하게 성장시키려는 많은 노력이 있어왔다. 또한 metal-ferroelectric-semiconductor field effect transistor)에서 ferroelectric 박막과 Si 기판사이의 완충층으로 사용된다. 이러한 CeO2의 응용을 위해서는 Si 기판 위에 성장된 CeO2 박막의 방위성 및 CeO2/Si 구조의 전기적 특성을 알아보는 것이 매우 중요하다. 본 연구에서는 Si(100) 기판위에 CeO2(200)방향으로 성장하는 박막과 EcO2(111) 방향으로 성장하는 박막을 rf magnetron sputtering 방법으로 증착하여 각각의 구조적, 전기적 특성을 분석하였다. RCA 방법으로 세정한 P-type Si(100)기판위에 Ce target과 O2를 사용하여 CeO2(200) 및 CeO2(111)박막을 증착하였다. 증착후 RTA(rapid thermal annealing)방법으로 95$0^{\circ}C$, O2 분위기에서 5분간 열처리를 하였다 이렇게 제작된 CeO2 박막의 구조적 특성을 XRD(x-ray diffraction)방법으로 분석하였고, Al/CeO2/Si의 MIS(metal-insulator-semiconductor)구조를 제작하여 C-V (capacitance-voltage), I-V (current-voltage) 특성을 분석하였으며 TEM(transmission electron microscopy)으로 증착된 CeO2막과 Si 기판과의 계면 특성을 연구하였다. C-V특성에 있어서 CeO2(111)/Si은 CeO2(111)의 두께가 증가함에 따라 hysteresis windows가 증가한 방면 CeO2(200)/Si은 hysteresis windows가 아주 작을뿐만 아니라 CeO2(200)의 두께가 증가하더라도 hysteresis windos가 증가하지 않았다. CeO2(111)/Si과 CeO2(200)/Si의 C-V 특성의 차이는 CeO2(111)과 CeO2(200)이 Si 기판에 의해 받은 stress의 차이와 이에 따른 defect형성의 차이에 의한 것으로 사료된다.

• Korean Journal of Materials Research
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• v.3 no.6
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• pp.661-667
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• 1993

Effects of $SiH_4//WF_6$(=R) ratio on the electrical properties of W films such as resistvity, contact resistance, junction leakage current in the selective W CVD technology for contact barrier metal were investigated with the emphasis on the role of $\alpha$-W Resistivity of W increases with increasing R, which is primarily due to the phase transformation from $\alpha$-W to , $\alpha$-W. $\alpha$-W found in the SiH4 reduced CVD W film is stabilized by Si incorporated into the W film rather than by oxygen. $\alpha$-W is found in the W film deposited on the Si substrate for high R, while $\alpha$-W is not found in the W film deposited on the TiN substrate even for high R. Also junction leakages increase with increasing R, which is caused not only by the vertical Si consumption but also the lateral Si consumption.