• Journal of Advanced Navigation Technology
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• v.7 no.2
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• pp.211-216
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• 2003

In this paper, characteristics of Ta-Ti alloy was studied as a gate electrode for NMOS devices to replace the widely used polysilicon. Ta-Ti alloy was deposited directly on $SiO_2$ by a co-sputtering method using two of Ta and Ti targets. The sputtering power of each metal target was 100W. To compare with Ta-Ti, Ta deposited with a 100W sputtering power was fabricated as well. In order to investigate the thermal/chemical stability of the Ta-Ti alloy gate, the alloy was annealed at $600^{\circ}C$ with rapid thermal annealer. No appreciable degradation of the device was observed. Also the results of electrical analysis showed that the work function of Ta-Ti metal alloy was about 4.1eV which was suitable for NMOS devices and sheet resistance of alloy was lower than that of polysilicon.

• Journal of Surface Science and Engineering
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• v.57 no.5
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• pp.386-397
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• 2024

Chrome plating is a method used to protect the inside of a gun barrel from the severe environment (3,000 K and 4,000 MPa for 20 ms) created by the propellant gas when a cannon is fired. However, Cr-plated films have physical limitations, and the formation of hexavalent Cr compounds has a harmful effect on the environment. Ta-W alloy film has been explored as an alternative to Cr plating owing to the high melting point and corrosion resistance of Ta. However, obtaining pure α-phase Ta by sputtering is difficult, and the autofrettage effect in gun barrels limits the use of annealing. Therefore, a deposition method without the use of additional heat treatment is required to prepare Ta-W films with alpha-phase Ta. We explored the feasibility of depositing Ta-W alloy film inside a 2,800 mm-long stainless-steel tube using bipolar high-power impulse magnetron sputtering. A specially designed cylindrical magnetron sputtering equipment and a four-stage experimental process was employed to deposit a coating with uniform thickness (10.59%) throughout the tube, high adhesive strength (51.51 MPa), and pure alpha-phase Ta. The findings of this study are useful for deposition of Ta-W alloy films inside large-caliber canons.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.9-12
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• 2004

This paper investigated the stability of Ta-Mo alloy on thin gate dielectric. Ta-Mo alloy was deposited by using co-sputtering process after thermal growing of 3.4nm and 4.2nm silicon dioxide. When the sputtering power of Ta and Mo were 100W and 70W, respectively, the suitable work function for NMOS gate electrode, 4.2eV, could obtain. To prove interface thermal stability of thin film gate dielectric and Ta-Mo alloy, rapid thermal annealing was performed at $600^{\circ}C$ and $700^{\circ}C$ for 10sec in Ar ambient. The results of interface reaction were surveyed by change of silicon dioxide thickness and work function after annealing process. Also, the reliability of alloy gate and gate dielectric could be confirmed by quantity of leakage current. Ta-Mo alloy was showed low sheet resistance and thermal stability, namely, little change of gate dielectric and work function, after $700^{\circ}C$ annealing process.

• Journal of Powder Materials
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• v.27 no.1
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• pp.52-57
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• 2020

In this study, we report the microstructure and characterization of Ta₂₀Nb₂₀V₂₀W₂₀Ti₂₀ high-entropy alloy powders and sintered samples. The effects of milling time on the microstructure and mechanical properties were investigated in detail. Microstructure and structural characterization were performed by scanning electron microscopy and X-ray diffraction. The mechanical properties of the sintered samples were analyzed through a compressive test at room temperature with a strain rate of 1 × 10^-4 s^-1. The microstructure of sintered Ta₂₀Nb₂₀V₂₀W₂₀Ti₂₀ high-entropy alloy is composed of a BCC phase and a TiO phase. A better combination of compressive strength and strain was achieved by using prealloyed Ta₂₀Nb₂₀V₂₀W₂₀Ti₂₀ powder with low oxygen content. The results suggest that the oxide formed during the sintering process affects the mechanical properties of Ta₂₀Nb₂₀V₂₀W₂₀Ti₂₀ high-entropy alloys, which are related to the interfacial stability between the BCC matrix and TiO phase.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.4 s.33
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• pp.23-27
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• 2004

The $Al_xTa_{1-x} (x=0.0{\~}1.0)$ alloy thin films were deposited by RF-magnetron sputtering system, and the crystal quality, surface morphology, and electrical properties were examined using XRD, AFM, 4-point probe techniques in this study. The thin films were grown according to the alloy compositions first, and the effects of film thickness and mask patterns were investigated afterwards. Also, the heating characteristics were examined by heat controller. The obtained results showed that the high electrical resistivity was obtained for Al content $x=6.63at\%$, and the even higher resistivity was accomplished for the samples with smaller thickness and narrower width. The heating temperature demonstrated the identical trend to the electrical properties, and the highest heating temperature ($400^{\circ}C$) and output power ($12.6W/cm^2$) were obtained for the sample with Al content $x=6.63\%$, film thickness d=500 nm, film width w=1.5 mm.

• Journal of Surface Science and Engineering
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• v.41 no.2
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• pp.69-75
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• 2008

Electrochemical behaviors of surface modified and MC3T3-E1 cell cultured Ti-30Ta alloys have been investigated using various electrochemical methods. The Ti alloys containing Ta were melted by using a vacuum furnace and then homogenized for 6 hrs at $1000^{\circ}C$. MC3T3-E1 cell culture was performed with MC3T3-E1 mouse osteoblasts for 2 days. The microstructures and corrosion resistance were measured using FE-SEM, XRD, EIS and potentiodynamic test in artificial saliva solution at $36.5{\pm}1^{\circ}C$. Ti-Ta alloy showed the martensite structure of ${\alpha}+{\beta}$ phase and micro-structure was changed from lamellar structure to needle-like structure as Ta content increased. Corrosion resistance increased as Ta content increased. Corrosion resistance of cell cultured Ti-Ta alloy increased predominantly in compared with non cell cultured Ti- Ta alloy due to inhibition of the dissolution of metal ion by covered cell. $R_p$ value of MC3T3-E1 cell cultured Ti-40 Ta alloy showed $1.60{\times}10^6{\Omega}cm^2$ which was higher than those of other Ti alloy. Polarization resistance of cell-cultured Ti-Ta alloy increased in compared with non-cell cultured Ti alloy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.15-18
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• 2003

Ta-Ti metal alloy is proposed for alternate gate electrode of ULSI MOS device. Ta-Ti alloy was deposited directly on $SiO_2$ by a co-sputtering method and good interface property was obtained. The sputtering power of each metal target was 100W. Thermal and chemical stability of the electrode was studied by annealing at $500^{\circ}C$ and $600^{\circ}C$ in Ar ambient. X-ray diffraction was measured to study interface reaction and EDX(energy dispersive X-ray) measurement was performed to investigate composition of Ta and Ti element. Electrical properties were evaluated on MOS capacitor, which indicated that the work function of Ta-Ti metal alloy was ${\sim}4.1eV$ compatible with NMOS devices. The measured sheet resistance of alloy was lower than that of poly silicon.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.483-486
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• 1995

Soft magnetic properties of Fe-based (Fe,Co)-B-Al-M (M=Nb, Mo or Ta) nanocrystalline alloy have been investigated. The alloy obtained directly form the rapid solidification process. Microstructure of the alloy is a mixtu re of ultrafine bcc Fe(Co) nanocrystallines and a small amount of retained amorphous phase. Heat treatment of as-prepared alloys improves soft magnetic properties in high frequency range. ${(Fe_{.85}Co_{.15})}_{70}B_{18}Al_{10}Ta_{6}$ alloy alloy annealed at $500^{\circ}C$ for 1 h shows the most improved soth magnetic properties among the alloy examined. Average grain size of the nanocystalline is about 10 nm.

• Korean Journal of Metals and Materials
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• v.50 no.2
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• pp.164-170
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• 2012

Nanotubular structure formation on the Ti-6Al-4V and Ti-Ta alloy surfaces by electrochemical methods has been studied using the anodizing method. A nanotube layer was formed on Ti alloys in 1.0 M $H_3PO_4$ electrolyte with small additions of $F^-$ ions. The nanotube nucleation and growth of the ${\alpha}$-phase and ${\beta}$-phase appeared differently, and showed different morphology for Cp-Ti, Ti-6Al-4V and Ti-Ta alloys. In the ${\alpha}$-phase of Cp-Ti and martensite ${\alpha}^{\prime}$ and in the ${\alpha}^{{\prime}{\prime}}$ and ${\beta}$-phase of the Ti-Ta alloy, the nanotube showed a clearly highly ordered $TiO_2$ layer. In the case of the Ti-Ta alloy, the pore size of the nanotube was smaller than that of the Cp-Ti due to the ${\beta}$-stabilizing Ta element. In the case of the Ti-6Al-4V alloy, the ${\alpha}$-phase showed a stable porous structure; the ${\beta}$-phase was dissolved entirely. The nanotube with two-size scale and high order showed itself on Ti-Ta alloys with increasing Ta content.

• Transactions of Materials Processing
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• v.33 no.5
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• pp.363-370
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• 2024

This study investigated the evolution behavior of microtexture developed in Ta-10W alloy during cold rolling. The changes in microtexture during the cold rolling process were experimentally analyzed using EBSD techniques. At relatively low rolling reductions (20%, 40%), θ-fiber and α-fiber textures were developed. However, as the reduction increased to 60% and 80%, strong α-fiber and γ-fiber textures were observed. The microtexture behavior was theoretically predicted using the VPSC polycrystal model under plane strain compression(PSC) and conditions considering deformation in the transverse direction. The VPSC model results under PSC predicted the strong development of θ-fiber texture at low reductions (20%, 40%) and the development of α-fiber and γ-fiber textures as the reduction increased to 60% and 80%. The VPSC model considering transverse deformation predicted results similar to the plane strain PSC at low reductions (20%, 40%), but as the reduction increased to 60% and 80%, it predicted that the development of α-fiber texture would be relatively weak, and the θ-fiber texture would still remain even at an 80% reduction. It was confirmed that the VPSC model considering transverse deformation more accurately predicts the evolution behavior of microtexture observed experimentally.