• 공업화학
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• 제27권6호
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• pp.653-658
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• 2016

본 연구에서는 1차원의 $MnO_2$ nanowire를 $KMnO_4$와 $MnSO_4$ 전구체 혼합물의 수열합성법(hydrothermal method)을 사용하여 제조할 수 있는 합성법을 개발하였다. 제조된 $MnO_2$ nanowire는 전기화학 반응 동안 전자와 이온전달을 용이하게 할 수 있는 넓은 비표면적과 기공구조를 나타내었다. MnO2 nanowire의 미세구조 및 화학구조를 주사형 전자현미경(SEM), 투과전자현미경(TEM), 광전자분석기(XPS), X-ray 회절분석법(XRD), 비표면적분석장비(BET)를 사용하여 분석하였다. 본 $MnO_2$ nanowire 전극의 전기화학적 특성은 순환전압전류법(cyclic voltammetry)과 정전류 충전-방전법(galvanostatic charge-discharge)을 사용하여 3상 전극 시스템(three-electrode system)에서 분석하였다. $MnO_2$ nanowire 전극은 높은 비정전용량(129 F/g), 고속 충방전(61% retention), 반 영구적인 수명특성(100%)을 나타내었다.

• 한국재료학회지
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• 제3권2호
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• pp.111-120
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• 1993

플라즈마 아크 용해에 의해 0.31-1.14at%Hf과 0.08-1.00at%C의 조성을 갖는 Mo시편을 제조하여, 열처리에 따른 미세조직 변화를 광학현미경, AES(Auger Electron Spectroscopy)및 투과전자현미경(TEM)으로 조사하였다. 산소함량이 약 830ppm인 초기분말을 압분체로 성형하여 용해한 결과, 산소함량 약 40-130ppm의 시편으로 제조할 수 있었으며, 이때 Hf및 C의 첨가량이 증가할수록 시편의 결정립은 미세화되었다. Mo-1.14at% Hf-1.00at % C 조성의 시편을 열처리한 결과 130$0^{\circ}C$에서 결정립내의 편상의 ${\beta}$-Mo 탄화물(molybdenum carbide)이 열역학적으로 더욱 안정한 $\alpha$-Mo 탄화물로 변태되기 시작하고, 1400-150$0^{\circ}C$온도 구간에서는 급내에 의해 고용되어 있던 Hf과 C이 반응하여 미량의 Hf탄화물이 석출되었으며, 150$0^{\circ}C$에서는 결정립계에 Hf 탄화물이 편석되었다. 1500-170$0^{\circ}C$에서는 결정립계에 편석된 Hf탄화물이 분해되고 열역학적으로 더욱 안정한 Hf 산화물(Hafnium oxide)이 석출되었으며, 결정립내에도 미세한 Hf 산화물이 석출되었다.

• 대한금속재료학회지
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• 제47권3호
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• pp.147-154
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• 2009

The effect of carbon addition on the microstructures and mechanical properties of $Ni_3Al$ and TiAl intermetallic alloys have been characterized. It is shown that carbon is not only an efficient solid solution strengthener in $Ni_3Al$ and TiAl, it is also an efficient precipitation strengthener by fine dispersion of carbide. Transmission electron microscope investigation has been performed on the particle-dislocation interactions in $Ni_3Al$ and TiAl intermetallics containing various types of fine precipitates. In an $L1_2$-ordered $Ni_3Al$ alloy with 4 mol.% of chromium and 0.2~3.0 mol.% of carbon, fine octahedral precipitates of $M_{23}C_6$ type carbide, which has the cube-cube orientation relationship with the matrix, appear during aging. Typical Orowan loops are formed in $Ni_3Al$ containing fine dispersions of $M_{23}C_6$ particles. In the L10-ordered TiAl containing 0.1~2.0 mol.% carbon, TEM observations revealed that needle-like precipitates, which lie only in one direction parallel to the [001] axis of the $L1_0$ matrix, appear in the matrix and preferentially at dislocations. Selected area electron diffraction (SAED) patterns analyses have shown that the needle-shaped precipitate is $Ti_3AlC$ of perovskite type. The orientation relationship between the $Ti_3AlC$ and the $L1_0$ matrix is found to be $(001)_{Ti3AlC}//(001)_{L10\;matrix}$ and $[010]_{Ti3AlC}//[010]_{L10\;matrix}$. By aging at higher temperatures or for longer period at 1073 K, plate-like precipitates of $Ti_2AlC$ with a hexagonal structure are formed on the {111} planes of the $L1_0$ matrix. The orientation relationship between the $(0001)_{Ti2AlC}//(111)_{L10\;matrix}$ is and $[1120]_{Ti2AlC}//[101]_{L10\;matrix}$. High temperature strength of TiAl increases appreciably by the precipitation of fine carbide. Dislocations bypass the carbide needles at further higher temperatures.

• 대한금속재료학회지
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• 제47권5호
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• pp.322-329
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• 2009

60 nm- and 20 nm-thick hydrogenated amorphous silicon (a-Si:H) layers were deposited on 200 nm $SiO_2/Si$ substrates using ICP-CVD (inductively coupled plasma chemical vapor deposition). A 10 nm-Ni layer was then deposited by e-beam evaporation. Finally, 10 nm-Ni/60 nm a-Si:H/200 nm-$SiO_2/Si$ and 10 nm-Ni/20 nm a-Si:H/200 nm-$SiO_2/Si$ structures were prepared. The samples were annealed by rapid thermal annealing for 40 seconds at $200{\sim}500^{\circ}C$ to produce $NiSi_x$. The resulting changes in sheet resistance, microstructure, phase, chemical composition and surface roughness were examined. The nickel silicide on a 60 nm a-Si:H substrate showed a low sheet resistance at T (temperatures) >$450^{\circ}C$. The nickel silicide on the 20 nm a-Si:H substrate showed a low sheet resistance at T > $300^{\circ}C$. HRXRD analysis revealed a phase transformation of the nickel silicide on a 60 nm a-Si:H substrate (${\delta}-Ni_2Si{\rightarrow}{\zeta}-Ni_2Si{\rightarrow}(NiSi+{\zeta}-Ni_2Si)$) at annealing temperatures of $300^{\circ}C{\rightarrow}400^{\circ}C{\rightarrow}500^{\circ}C$. The nickel silicide on the 20 nm a-Si:H substrate had a composition of ${\delta}-Ni_2Si$ with no secondary phases. Through FE-SEM and TEM analysis, the nickel silicide layer on the 60 nm a-Si:H substrate showed a 60 nm-thick silicide layer with a columnar shape, which contained both residual a-Si:H and $Ni_2Si$ layers, regardless of annealing temperatures. The nickel silicide on the 20 nm a-Si:H substrate had a uniform thickness of 40 nm with a columnar shape and no residual silicon. SPM analysis shows that the surface roughness was < 1.8 nm regardless of the a-Si:H-thickness. It was confirmed that the low temperature silicide process using a 20 nm a-Si:H substrate is more suitable for thin film transistor (TFT) active layer applications.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.239-240
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• 2008

As semiconductor devices are scaled down for better performance and more functionality, the Cu-based interconnects suffer from the increase of the resistivity of the Cu wires. The resistivity increase, which is attributed to the electron scattering from grain boundaries and interfaces, needs to be addressed in order to further scale down semiconductor devices [1]. The increase in the resistivity of the interconnect can be alleviated by increasing the grain size of electroplating (EP)-Cu or by modifying the Cu surface [1]. Another possible solution is to maximize the portion of the EP-Cu volume in the vias or damascene structures with the conformal diffusion barrier and seed layer by optimizing their deposition processes during Cu interconnect fabrication, which are currently ionized physical vapor deposition (IPVD)-based Ta/TaN bilayer and IPVD-Cu, respectively. The use of in-situ etching, during IPVD of the barrier or the seed layer, has been effective in enlarging the trench volume where the Cu is filled, resulting in improved reliability and performance of the Cu-based interconnect. However, the application of IPVD technology is expected to be limited eventually because of poor sidewall step coverage and the narrow top part of the damascene structures. Recently, Ru has been suggested as a diffusion barrier that is compatible with the direct plating of Cu [2-3]. A single-layer diffusion barrier for the direct plating of Cu is desirable to optimize the resistance of the Cu interconnects because it eliminates the Cu-seed layer. However, previous studies have shown that the Ru by itself is not a suitable diffusion barrier for Cu metallization [4-6]. Thus, the diffusion barrier performance of the Ru film should be improved in order for it to be successfully incorporated as a seed layer/barrier layer for the direct plating of Cu. The improvement of its barrier performance, by modifying the Ru microstructure from columnar to amorphous (by incorporating the N into Ru during PVD), has been previously reported [7]. Another approach for improving the barrier performance of the Ru film is to use Ru as a just seed layer and combine it with superior materials to function as a diffusion barrier against the Cu. A RulTaN bilayer prepared by PVD has recently been suggested as a seed layer/diffusion barrier for Cu. This bilayer was stable between the Cu and Si after annealing at $700^{\circ}C$ for I min [8]. Although these reports dealt with the possible applications of Ru for Cu metallization, cases where the Ru film was prepared by atomic layer deposition (ALD) have not been identified. These are important because of ALD's excellent conformality. In this study, a bilayer diffusion barrier of Ru/TaCN prepared by ALD was investigated. As the addition of the third element into the transition metal nitride disrupts the crystal lattice and leads to the formation of a stable ternary amorphous material, as indicated by Nicolet [9], ALD-TaCN is expected to improve the diffusion barrier performance of the ALD-Ru against Cu. Ru was deposited by a sequential supply of bis(ethylcyclopentadienyl)ruthenium [Ru$(EtCp)_2$] and $NH_3$plasma and TaCN by a sequential supply of $(NEt_2)_3Ta=Nbu^t$ (tert-butylimido-trisdiethylamido-tantalum, TBTDET) and $H_2$ plasma. Sheet resistance measurements, X-ray diffractometry (XRD), and Auger electron spectroscopy (AES) analysis showed that the bilayer diffusion barriers of ALD-Ru (12 nm)/ALD-TaCN (2 nm) and ALD-Ru (4nm)/ALD-TaCN (2 nm) prevented the Cu diffusion up to annealing temperatures of 600 and $550^{\circ}C$ for 30 min, respectively. This is found to be due to the excellent diffusion barrier performance of the ALD-TaCN film against the Cu, due to it having an amorphous structure. A 5-nm-thick ALD-TaCN film was even stable up to annealing at $650^{\circ}C$ between Cu and Si. Transmission electron microscopy (TEM) investigation combined with energy dispersive spectroscopy (EDS) analysis revealed that the ALD-Ru/ALD-TaCN diffusion barrier failed by the Cu diffusion through the bilayer into the Si substrate. This is due to the ALD-TaCN interlayer preventing the interfacial reaction between the Ru and Si.