• 한국분말재료학회지
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• 제6권4호
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• pp.314-319
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• 1999

The solid state reaction by mechanical alloying(MA) generally proceeds by lowering the free energy as the result of a chemical reaction at the interface between the two adjacent layers. However, Lee et $al.^{1-5)}$ reported that a mixture of Cu and Ta, the combination of which is characterized by a positive heat of mixing of +2kJ/mol, could be amorphized by mechanical alloying. This implies that there exists an up-hill process to raise the free energy of a mixture of pure Cu and la to that of an amorphous phase. It is our aim to investigate to what extent the MA is capable of producing a non-equilibrium phase with increasing the heat of mixing. The system chosen was the ternary $Cu_{30}Ta_{ 70-x}Mo_ x$ (x=35, 10). The mechanical alloying was carried out using a Fritsch P-5 planetary mill under Ar gas atmosphere. The MA powders were characterized by the X-ray diffraction with Cu-K $\alpha$ radiation, thermal analysis, electron diffraction and TEM micrographs. In the case of x=35, where pure Cu powders were mixed with equal amount of pure Ta and Mo powders, we revealed the formation of bcc solid solution after 150 h milling but its gradual decomposition by releasing fcc-Cu when milling time exceeded 200 h. However, an amorphous phase was clearly formed when the Mo content was lowered to x=10. It is believed that the amorphization of ternary $Cu_{30}Ta_{60}Mo_{10}$ powders is essentially identical to the solid state amorphization process in binary $Cu_{30}Ta_{70}$ powders.

• 한국전기전자재료학회논문지
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• 제16권2호
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• pp.108-112
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• 2003

The calculated and measured dielectric constants of (1-x)(A $l_{1}$2/ T $a_{1}$2/) $O_2$-x(M $g_{1}$3/ T $a_{2}$3/) $O_2$ (0$\leq$x$\leq$1.0) solid solutions were investigated by variations of ionic polarizability and crystal structure. (A $l_{1}$2/ T $a_{1}$2/) $O_2$ and (M $g_{1}$3/ T $a_{2}$3/) $O_2$ were orthorhombic and tetragonal trirutile structure, respectively. When (A $l_{1}$2/ T $a_{1}$2/) $O_2$ was substituted by (M $g_{1}$3/ T $a_{2}$3/) $O_2$, the phase transformed to tetragonal structure over 60 mole. Because the total ionic radius of [(Mg+2Ta)/3]$^{4+}$ was slightly bigger than one of [(Al+Ta)/2]$^{4+}$, the lattice parameters increased with an increase of (M $g_{1}$3/ T $a_{2}$3/) $O_2$ substitution. The measured dielectric constant increased with an increase of (M $g_{1}$3/ T $a_{2}$3/) $O_2$ substitution and coincided with dielectric mixing rule and the calculated dielectric constant with the molecular additivity rule. There were some differences between the measured and the calculated dielectric constant. The reason of the lowered dielectric constant comparing with the calculated one was compressed stress due to the electronic structure of tantalum.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.162-162
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• 2012

Sub 100 nm의 Complementary Metal-Oxide-Semiconductor (CMOS) 소자를 구동하기 위해서는 2.0 nm 이하의 $SiO_2$ oxide에 해당하는 전기적 특성이 요구된다. 그러나 2.0 nm 이하의 $SiO_2$에서는 누설 전류가 너무 크기 때문에 이를 대체하기 위해서 유전 상수 (dielectric permittivity)가 높은 $HfO_2$ (${\varepsilon}=25$), $Al_2O_3$, $HfO_2/Al_2O_3$ laminate 등의 high-k dielectric 물질들이 연구되고 있다[1]. High-k dielectric 물질의 전기적 특성은 박막 조성, 두께 및 전극과의 계면에 생성되는 계면 층이나 불순물(Impurity) 거동에 크게 의존하므로 High-k dielectric/전극(Metal or Si) 구조에서 조성 및 불순물의 거동에 대한 정확한 평가가 주요 쟁점으로 부각되고 있다. 이를 평가하기 위해 일반적으로 $Ar^+$ ion에 의한 depth profiling 분석이 진행되나 Oxygen 원자의 선택적 식각에 기인된 분석 깊이 분해능(Depth Resolution) 왜곡으로 계면 층의 형성이나 불순물의 거동을 정확하게 평가할 수 없다. 이러한 예로는 $Ta_2O_5$ 및 $SrBi_2Ta_2O_9$와 같은 다 성분 계 산화막에 $Ar^+$ ion 주사 시 발생하는 선택적인 식각(Preferential Sputtering) 때문에 박막의 실제 조성 및 거동을 평가하는 것은 어렵다고 보고된 바 있다[2,3]. 본 연구에서는 $90{\AA}$인 적층 $Hf_xO_y/Al_xO_y/Hf_xO_y$ 구조에서의 불순물 거동 분석 능력 확보 상 주요 인자인 깊이 분해능 개선을 Secondary Ion Mass Spectroscopy(SIMS)의 primary ion 종, impact energy 및 주사 각도를 변화시켜 ~1 nm 수준까지 구현하였다. 이러한 분석 깊이 분해능의 개선은 Low Impact Energy, 입사 이온의 glancing angle 및 Cluster ion 적용에 의존하며 이들 요인의 효과에 대해 비교/고찰하고자 한다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제1권4호
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• pp.202-208
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• 2001

In Recent results suggested that doping $Ta_2O_5$ with a small amount of $TiO_2$ using standard ceramic processing techniques can increase the dielectric constant of $Ta_2O_5$ significantly. In this paper, this concept is studied using RTCVD (Rapid Thermal Chemical Vapor Deposition). Ti-doped $Ta_2O_5$ films are deposited using $TaC_{12}H_{30}O_5N$, $C_8H_{24}N_4Ti$, and $O_2$ on both Si and $NH_3$-nitrided Si substrates. An $NH_3$-based interface layer at the Si surface is used to prevent interfacial oxidation during the CVD process and post deposition annealing is performed in $H_2/O_2$ ambient to improve film quality and reduce leakage current. A sputtered TiN layer is used as a diffusion barrier between the Al gate electrode and the $TaTi_xO_y$ dielectric. XPS analyses confirm the formation of a ($Ta_2O_5)_{1-x}(TiO_2)_x$ composite oxide. A high quality $TaTi_xO_y$ gate stack with EOT (Equivalent Oxide Thickness) of $7{\AA}$ and leakage current $Jg=O.5A/textrm{cm}^2$ @ Vg=-1.0V has been achieved. We have also succeeded in forming a $TaTi_x/O_y$ composite oxide by rapid thermal oxidation of the as-deposited CVD TaTi films. The electrical properties and Jg-EOT characteristics of these composite oxides are remarkably similar to that of RTCVD $Ta_2O_5, suggesting that the dielectric constant of $Ta_2O_5$ is not affected by the addition of $TiO_2$.

• 한국재료학회지
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• 제14권3호
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• pp.211-217
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• 2004

The oxidation behaviors of Ti-10Ta-10Nb alloy and Ti-6Al-4V alloy were studied in dry air atmosphere. Specimens were melted in consumable vacuum arc furnace and homogenized at $1050^{\circ}C$ for 24 h. Hot rolling was performed at $1000^{\circ}C$. Specimens of the alloys were oxidized as the temperature range $400~650^{\circ}C$ for 30 min. The oxidation behavior of the alloys was analysed by optical microscope, SEM/EDX, XRD, XPS and TGA. Immersion test was performed in 1% Lactic acid. In the microscope observation, oxide layer of Ti-10Ta-10Nb alloy was denser and thinner than Ti-6Al-4V's. The weight gains during the oxidation rapidly increased at the temperature above $600^{\circ}C$ in Ti-6Al-4V's alloy and$ 700^{\circ}C$ in Ti-10Ta-10Nb alloy. According to XRD results, oxide layers were composed of mostly $TiO_2$(rutile) phase. It was analysed that the passive film of the Ti alloys consisted of $TiO_2$ through X-ray photoelectron spectroscopy(XPS) analysis.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권8호
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• pp.340-346
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• 2002

Capacitor material utilized in the downsizing passive devices and integration of passive devices requires the physical and electrical properties at given area such as capacitor thickness reduction, relative dielectric constant increase, low leakage current and thermal stability. common capacitor materials, $Al_2O_3$, $SiO_2$, $Si_3N_4$, $SiO_2$/$Si_3N_4$, TaN and et al., used until recently have reached their physical limits in their application to integration of passive devices. $Ta_2O_{5}$ is known to be a good alternative to the existing materials for the capacitor application because of its high dielectric constant (25~35), low leakage current and high breakdown strength. Despite the numerous investigations of $Ta_2O_{5}$ material, there have little been established the clear understanding of the annealing effect on capacitance characteristic and conduction mechanism. This study presents the dielectric properties $Ta_2O_{5}$ MIM capacitor structure Processed by $O_2$ RTA oxidation. X-ray diffraction patterns showed the existence of amorphous phase in $600^{\circ}C$ annealing under the $O_2$ RTA and the formation of preferentially oriented-$Ta_2O_{5}$ in 650, $700^{\circ}C$ annealing and the AES depth profile showed $O_2$ RTA oxidation effect gives rise to the $O_2$ deficientd into the new layer. The leakage current density respectively, at 3~1l$\times$$10_{-2}$(kV/cm) were $10_{-3}$~$10_{-6}$(A/$\textrm{cm}^2$). In addition, behavior is stable irrespective of applied electric field. the frequency vs capacitance characteristic enhanced stability more then $Ta_2O_{5}$ thin films obtained by $O_2$ reactive sputtering. The capacitance vs voltage measurement that, Vfb(flat-band voltage) was increase dependance on the $O_2$ RTA oxidation temperature.

• 한국세라믹학회지
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• 제40권10호
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• pp.925-930
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• 2003

The dielectric polarizability-related factors contributing to the $\tau$$_{\varepsilon}$ have been analysed in terms of dielectric permittivity $\varepsilon$, Tolerance Factor (TF), and octahedron tilt angles in (1-x)CaTi $O_3$-x[A(B', B″) $O_3$] (A=Ca, La, Li, B'=Al, Fe, Mg, B″=Nb, Ta) and (S $r_{0.2}$C $a_{0.8}$)( $Ti_{1-x}$ Z $r_{x}$) $O_3$. All the compounds have the orthorhombic Pbnm structure except the end members A(B', B″) $O_3$ and the solid solutions of x$\geq$0.8. The additional dipole field effect is suggested as a dominant factor contributing to $\tau$$_{\varepsilon}$ in CaTi $O_3$-based ceramics having relatively large $\varepsilon$, which has not been generally considered in the previous reports dealing with the $\tau$$_{\varepsilon}$. This study has been focussed on delineating the dipole field effect on the $\tau$$_{\varepsilon}$ in comparison to the octahedron tilt effect in CaTi $O_3$-based ceramics.cs..cs.

• 대한치과기공학회지
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• 제26권1호
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• pp.97-104
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• 2004

A new Ti-10Ta-10Nb alloy has designed and examined some possibility of forming more passive oxide film by oxidation treatment which is closely related to corrosion resistance and biocompatibility. Ti-6Al-4V and Ti-10Ta-10Nb alloys were prepared by consumable vacuum arc melting and homogenized at 1050$^{\circ}C$ for 24hours. Alloy specimens were oxidized at the temperature range of 400 to 750$^{\circ}C$ for 30minutes, and the oxide films on Ti alloys were analysed by optical microscope, SEM, XPS and TGA. Cytotoxicity test was performed in MTT assay treated L929 fibroblast cell culture by indirect method. It is found out that the oxide film on Ti-10Ta-10Nb alloy is denser and thinner compared to Ti-6Al-4V alloy. The weight gain during the oxidation was increased rapidly at the temperature above 650$^{\circ}C$ for Ti-6Al-4V alloy and above 700$^{\circ}C$ for Ti-10Ta-10Nb alloy respectively. It was analysed that the passive film of the Ti alloys consisted of TiO2 through X-ray photoelectron spectroscopy (XPS) analysis. It is found out by cytotoxicity test that moderate oxidation treatment lowers cell toxicity, and Ti-10Ta-10Nb alloy showed better result compared to Ti-6Al-4V alloy.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 춘계학술발표강연 및 논문개요집
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• pp.219-219
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• 2003

HVOF(High Velocity Oxygen Fuel)법을 사용한 MCrAlY(M=Ni, Co, Fe)계 열차폐 코팅(thermal barrier coating)은 열기관 내부의 극심한 환경 부하에 대해 구조물 표면에 열적, 화학적 장벽을 형성함으로써 구조물의 내구성을 향상시킨다 이와 동시에 열차폐 효과는 구조물의 온도상승 없이 내부 가동 온도를 높일 수 있게 함으로써 열효율을 상승시키고 연료 효율을 높여 가동비용 절감을 이룰 수 있는 동시에 고 연소를 통한 오염원의 배출을 감소시킬 수 있다. 본 연구에서는 $H_2O$$_2$=5:1 분위기 하에서 HVOF법을 사용하여 Hastelloy-X 기판위에 125$\mu\textrm{m}$의 두께로 다음 5종류의 (Ni, Co, Cr)계 MCrAlY 코팅을 용사시켰다. 준비된 (Ni, Co)-Cr-Al-(Y, Ta, Re), (Ni, Co)-Cr-Al-(Y, Re), (Ni, Co)-Cr-Al-(Y, Ta), (Ni, Co)-Cr-Al-Y, (Ni,Co)-Cr-Al-Ir 코팅시편에 대한 산화성질을 조사하기 위해 대기 중 1000, 1100, 120$0^{\circ}C$에서 50, 100, 150, 200시간 등온실험(Isothermal oxidation)을 실시하였고, XRD, SEM/EDS, EPMA를 이용하여 생성된 산화막과 코팅 시편의 조직 변화를 조사하였다. 산화온도와 산화시간이 증가할수록 산화막의 박리가 많이 발생하였으며, 분석 결과 미세하게 분포된 a-Al$_2$O$_3$ 입자, NiCr$_2$O$_4$스피넬 상, 미세한 Cr$_2$O$_3$가 관찰되었고, 코팅 조성 변화에 따라 형성되는 이들 산화물의 존재비가 달라졌으며, 산화온도가 높아질수록 산화속도가 가속화되었다.

• 열처리공학회지
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• 제36권3호
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• pp.145-152
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• 2023

β titanium alloys containing β stabilizing elements such as V, Nb, Ta, Mo and Fe are widely used etc, due to their excellent specific strength, corrosion resistance, fatigue strength and easy formability. New metastable β titanium alloys are developed containing low-cost elements (Mo and Fe) in this study. Fe element is a strong β-stabilizer which can affect the mechanical and electrochemical properties of Ti-5Mo-xFe (x = 1, 4 wt%) alloys. These properties were analyzed in connection with microstructure and phase distribution. Ti-5Mo-4Fe alloy showed higher compression yield stress and maximum stress than Ti-5Mo-1Fe alloy due to solid-solution hardening and grain refinement hardening effect. As Fe element increased, Fe oxide formation and reduction of ${\bar{Bo}}$ (bond order) value affect the decrease of corrosion resistance. Ti-5Mo-xFe alloys were more excellent than Ti-6Al-4V ELI alloy.