• Journal of the Korean Ceramic Society
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• v.33 no.4
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• pp.405-410
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• 1996

The partial substitution of LiTaO3 with Al2O3 caused the variation of dielectric properties and a lower melting temperature yielding an easier growth of single crystal. The lattice constants and Raman band broadening were measured for the LiTaO3 solid solution in which the cations of Li+ and Ta5+ were partially substituted by Al3+ cation. The LiTaO3 type limit phases were obtained. ; Li1.15Al0.45Ta0.7O3 for cationic excess Li1.15Al0.45Ta0.7O3 for stoichiometry Li0.85Al0.05TaO3 for cationic deficit. The second phase was formed beyond the solubility limit. The limit phase (Li0.85Al0.05TaO3) in the region of cationic deficit showed the lowest Cuire temperature of 61$0^{\circ}C$ and melting point of 152$0^{\circ}C$ compared to the solid solutions in other regions (TMp=1$650^{\circ}C$, Tc=69$0^{\circ}C$ for LiTaO3)

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.60-63
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• 1999

Application of reactive ion etching (RIE) technique to Ta-Al alloy thin film with a thickness of $1000{\AA}$ was studied. $CF_{4}$ gas could be used effectively to etch the Ta-Al alloy thin film. The etching rate in the thin film with Ta content of 50 mol% was about $67{\AA}/min$. NO selectivity between the Ta-Al alloy film and $SiO_{2}$ film was observed during the etching using the $CF_{4}$ gas. The etching rate of the $SiO_{2}$ layer was 12 times faster than that of the Ta-Al alloy thin film. It was also observed that photoresist of AZ5214 was more useful than Shiepley 1400-27 in RIE with the $CF_{4}$ gas.

• Journal of Surface Science and Engineering
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• v.39 no.3
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• pp.129-136
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• 2006

The high velocity oxy-fuel sprayed coatings of 38Ni-23Co-20Cr-11Al-3Y-5Ta, 25Ni-34Co-20Cr-11Al-3Y-2Re and 32Ni-34.5Co-22Cr-11Al-0.5Ir (in wt%) were oxidized at 1000 and $1100^{\circ}C$ in air in order to find the alloying effect of Ta, Re and Ir on the oxidation properties of the NiCoCrAlY-base coatings. The primary phase of the coatings was $Ni_3Al$. The oxides formed on the coatings consisted primarily of ${\alpha}-Al_2O_3$, together with some $CoCr_2O_4,\;CoAl_2O_4$, and $Al_5Y_3O_{12}$. Tantalum oxidized to $Ta_2O_5$ and $Ta_2O_{22}$. However, no oxides of Re and Ir were detected by XRD owing to their thermodynamic inertness and/or their small amount.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.09a
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• pp.85-90
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• 1998

Reactive ion etching (RIE) of Ta-Al alloy thin film and SiO2 thin films was observed during the etching with the CF4 gas and the could be used effectively to etch the Ta-Al alloy thin film. The etching rate of the thin film at a Ta content of 50 mol% was about 67$\AA$/min. No selectivity between the Ta-Al alloy thin film and SiO2 thin films was observed during the etching with the CF4 gas and the etching rate of the SiO2 layer was 12 times faster than that of the Ta-Al alloy thin film. In addition, it was observed that photoresist of AZ5214 was more useful than Shiepley 1400-2 in RIE with the CF4 gas.

• Korean Journal of Materials Research
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• v.4 no.7
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• pp.759-766
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• 1994

Our investigation aimed to reduce the leakage current of $Ta_2O_5$ thin film capacitor by layering SnOz thin film layer under Ta thin film, thereby supplying extra oxygen ions from the $SnO_{2}$ underlayer to enhance the stoichiometry of $Ta_2O_5$ during the oxidation of Ta thin film. Tantalum was evaporated by e-beam or sputtered on p-Si wafers with various deposition temperatures and was oxidized by dry--oxygen at the temperatures between $500^{\circ}C$ and $900^{\circ}C$. Aluminum top and bottom electrodes were formed to make Al/$Ta_2O_5$/p-Si/Al or $Al/Ta_2O_5/SnO_2$p-Si/AI MIS type capacitors. LCR meter and pico-ammeter were used to measure the dielectric constants and leakage currents of the prepared thm film capacitors. XRD, AES and ESCA were employed to confirm the crystallization of the thin f~lm and the compositions of the films. Dielectric constant of $Ta_2O_5$ thin film capacitor with $SnO_{2}$ underlayer was found to be about 200, which is about 10 times higher than that of $Ta_2O_5$ thin film capacitor without $SnO_{2}$ underlayer. In addition, higher oxidation temperatures increased the dielectric constants and reduced the leakage current. Higher deposition temperature generally gave lower leakage current. $Ta_2O_5/SnO_2$ capacitor deposited at $200^{\circ}C$ and oxidized at $800^{\circ}C$ showed significantly lower leakage current, $10^{-7}A/\textrm{cm}^2$ at $4 \times 10^{5}$V/cm, compared to the one without $SnO_{2}$ underlayer. XRD showed that $Ta_2O_5$ thin film was crystallized above $700^{\circ}C$. AES and ESCA showed that initially the $SnO_{2}$, underlayer supplied oxygen ions to oxidize the Ta layer, however, Sn also diffused into the Ta thin film layer to form a new $Ta_xSn_YO_Z$ , ternary oxide layer after all.

• Journal of the Korean Ceramic Society
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• v.47 no.5
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• pp.461-466
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• 2010

In this study, $Al_2O_3/TaAlO_4/SiO_2$ (A/TAlO/S) structures with tantalum aluminate charge trap layer were fabricated for Nand flash memory device. We evaluated the memory window and retention characteristic as the thickness of the tunnel oxide was varied among 3 nm, 4 nm, and 5 nm. All tunnel oxide thicknesses were measured by ellipsometer and TEM (Transmission Electron Microscope). The A/TAlO/S multi-layer film consisted of 5 nm tunnel oxide showed the best result of memory window of 1.57 V and retention characteristics. After annealing the 5 nm tunnel oxide A/TAlO/S multi-layer film at $900^{\circ}C$. The memory window decreased to 1.32 V. Moreover, the TEM images confirmed that the thickness of multi-layer structure decreased 14.3% after annealing and the program conditions of A/TAlO/S multi-layer film decreased from 13 V to 11 V for 100 ms. Retention properties of both as-deposited and annealed films stably maintained until to $10^4$ cycles.

• Journal of Surface Science and Engineering
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• v.33 no.4
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• pp.251-260
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• 2000

Ta and Hf added Ti-l5Sn-4Nb alloys without V and Al elements for biomaterial were melted by arc furnace in response to recent concerns about the long term safety of Ti-6Al-4V alloy. All specimens were homogenized at $1000^{\circ}C$ and solution treatment was performed at $812^{\circ}C$ and aging treatment at $500^{\circ}C$. The microstructure and mechanical properties were analysed by optical micrograph, hardness tester and instron. Ti-l5Sn-4Nb system alloys showed widmanstatten microstructure which is typical microstructure in $\alpha$＋$\beta$ type Ti alloys. The Ti-l5Sn-4Nb-2Hf and Ti-l5Sn-4Nb-2Ta alloys showed better hardness and tensile strength compared with Ti-6Al-4V. The result of XPS analysis, Ti-l5Sn-4Nb alloy in air atmosphere consisted of $TiO_2$, SnO and NbO.

• Journal of the Mineralogical Society of Korea
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• v.2 no.1
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• pp.8-10
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• 1989

Sphene from the McDonald pegmatite near Bancroft, Ontario, Canada was analyzed using EPMA. It contains 4.3 to 6.3 weight percent of Nb2O5 with an average formula Ca1.02(Ti0.62Al0.22Nb0.07Fe0.06Ta0.01)Si0.99(O4.85F0.16). Three types of subtitutions are possible; 1)2Ti4+=(Nb, Ta)5+ + (Al, Fe3+), 2) Ti + O = (Al, Fe3+) + (F, OH), and 3) 2Ti + O = Fe2+ + (Nb, Ta)5+ + (F, OH). T재 different schemes of substitutions for balancing the analysis are considered when the iron is either all ferric or all ferrous. Assuming stoichiometry fo Ca and Si, a general formula derived from the two different schemes is Ca(Ti0.64Al0.22Fe3+0.06-X {{{{Fe_{x}^{2+} }} Nb0.01)Sio4.80-XF0.16(OH)0.04+x.

• Journal of the Korean Magnetics Society
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• v.11 no.5
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• pp.196-201
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• 2001

The dependence of CoFe interfacial layer thickness and plasma oxidation condition on tunneling magnetoresistance (TMR) in Ta/NiFe/FeMn/NiFe/Al$_2$O$_3$/NiFe/Ta tunnel junctions was investigated. As the CoFe layer thickness increases, TMR ratio rapidly increases to 13.7 % and decreases with further increase of the CoFe layer thickness. The increase of TMR with the CoFe thickness up to 25 was thought to be due mails to the high spin-polarization of CoFe. The maximum MR of 15.3% was obtained in the Si(100)/Ta(50 )/NiFe(60 )/FeMn(250 )/NiFe(70 )/Al$_2$O$_3$/NiFe(150 )/Ta(50 ) magnetic tunnel junction with a 16 Al oxidized for 40 sec using a Ar/O$_2$ (1:4) mixture gas.

• Korean Journal of Materials Research
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• v.14 no.3
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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.