• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.2
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• pp.193-204
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• 1998

The single crystal of the $LiTaO_3$has large electro-optic effects, so it is applied to optical switch, acousto-optic deflector, and optical memory device as hologram using photorefractive effect. In this study, optic-grade undoped $LiTaO_3$and Fe:LiTaO$LiTaO_3$single crystals were grown by the Czochralski method and optical transmission and absorption spectrums were measured in the wavelength of UV-VIS range. The curie temperature was determined with DSC and by measuring capacitance for the grown undoped crystal and ceramic powder samples of various Li/Ta ratio. In case of having a 48.6 mol% $Li_2O$ as a starting Li/Ta ratio, the results of concentration variations were below 0.01 mol% $Li_2O$ all over the crystal, so it was confirmed that $LiTaO_3$single crystals were grown under congruent melting composition having optical homogeneity. The curie temperature of the Fe:$LiTaO_3$crystal was increased with increased with increased doped Fe concentrations;by the ratio of $7.5^{\circ}C$ increase per Fe 0.1 wt%. Also, the optical transmittance was about 78 %, which was sufficient for optical device.

• Korean Journal of Materials Research
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• v.9 no.6
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• pp.551-555
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• 1999

The deposition condition to obtain stoichiometric $Ta_2$O\ulcorner films, which is still controversial, using magnetron reactive sputtering was studied. The films were deposited by varying $O_2$gas flow rate with sputtering power and Ar gas flow rate of 200W and 60 sccm fixed. At the conditions of $O_2$ gas flow rate over 20 sccm, amorphous Tantalum oxide films with the refractive index of 2.1 and dielectric constant of 25 were deposited. Among those films, the capacitors dielectric properties of the film deposited at the condition of $O_2$ gas flow rate 50 sccm was best, the leakage current was 1$\times$10\ulcornerA/$\textrm{cm}^2$ at the electric field strength of 0.5 MC/cm and the breakdown field strength was over 2.0 MV/cm. This result could be explained from the analysis comparing with a standard sample using RBS because the composition of the film deposited at this condition was closest to the stoichiometric $Ta_2$O\ulcorner. The result of XPS analysis convinced that this film was stoichiometric $Ta_2$O\ulcorner film. A maximum cathode voltage was observed when $O_2$gas flow rate was 30 sccm. This shows that the Schiller's proposition that one can obtain stoichiometric films at the condition of maximum cathode voltage is not correct and more oxygen than that of the maximum voltage condition is necessary to deposit the stoichiometric Ta$_2$O\ulcorner films.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.57-57
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• 2003

High dielectric constant materials (high K) have attracted a great deal of interest because of the dramatic scaling down of DRAM capacitor reaching its physical limit in terms of reduction of thickness. Among high-K materials that can replace silicon dioxide, tantalum pentoxide (Ta2O5) thin film, with their high dielectric constant (∼25) and good step coverage, is the candidate of choice.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1561-1569
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• 1994

Effect of calcining temperature on the sintering behaviors and microwave dielectric properties of BMT[Ba(Mg1/3Ta2/3)O3] ceramics was studied. The calcining temperatures were varied from 80$0^{\circ}C$ to 130$0^{\circ}C$, respectively. It was found that, as calcining temperature lowered below 125$0^{\circ}C$, second phase such as Ba5Ta4O15 phases started to appear in calcined powder with unreacted powders. After sintering, exaggerately grown Ba5TaO3 phase could be found amang the uniform BMT grains in sintered body. Basis on the infiltration experiment, Ba0.05TaO3 phase should be formed by reaction of BMT grain and BaO-MgO eutectic liquid. But increase of calcining temperature above 125$0^{\circ}C$, there was not any second phase or unreated component in calcined powder and sintered body. As result, low calcining temperature led to precipitation of second phase in specimen and resulted decrease of Q value of BMT ceramics.

• 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.

• Korean Journal of Materials Research
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• v.16 no.6
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• pp.373-376
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• 2006

[ $Ba(Mg_{1/3}Ta_{2/3})O_3$ ] nanoparticles were synthesized in water solution under mild temperature and pressure conditions by precipitation from $Ba(NO_3),\;Mg(NO_3)_2{\cdot}6H_2O\;and\;TaCl_5$ with aqueous potassium hydroxide. The average size and distribution of the synthesized $Ba(Mg_{1/3}Ta_{2/3})O_3$ nanoparticles were below 100 nm and broad, respectively. The phase of synthesized particles was crystalline reacted at $170^{\circ}C$ for 4 h. The characterization of $Ba(Mg_{1/3}Ta_{2/3})O_3$ nanoparticles were studied using XRD, SEM, and TEM.

• Analytical Science and Technology
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• v.5 no.1
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• pp.111-114
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• 1992

Ordering phenomena were observed for Zn and Ta cations of $Ba(Zn_{1/3}Ta_{2/3})O_3$ under particular heat treatments, followed by a considerable lattice distortion. This lattice distortion was measured by X-ray powder diffraction with a precision of higher than 1/10,000. From this investigation, a significant lattice distortion occurred within 30 min. of sintering at $1350^{\circ}C$, and it was increased with sintering time.

• Journal of the Korean Chemical Society
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• v.28 no.5
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• pp.293-301
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• 1984

-ray fluorescence analysis of $Ta_2O_5$, $Nb_2O_5$ and $ZrO_2$ in tin-slag samples using the simple dilution method was studied. The method is to correct mathematically the calibration curve to the linear line by the dilution. One synthesized standard having similar composition to the sample and tin slag samples were diluted with anhydrous $Li_2B_4O_7$ at the level of 1%, 2% and 3% of the sample content respectively. The diluted samples were fused at $1150^{\circ}C$ for 30 minutes and these glass beads were finely ground and pelletized. Measuring the X-ray intensities with these pellets, analytical results were calculated by the equation derived from J. Scherman's equation for the characteristic X-ray intensity of an element. Analytical results agreed with the reference values obtained by the standard calibration method within allowable error range and were reproducible.

• Journal of the Korean Vacuum Society
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• v.2 no.2
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• pp.246-254
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• 1993

In order to increase the capacitance of storage electrode in the DRAM capacitor, two approaches were performed. First, hemispherical and rugged poly silicon films were made by LPCVD to increase the effective surface area of storage electrode. The even surface morphology of conventional poly silicon electrode was changed into the uneven surface of hemispherical of rugged poly silicon films. Second, PECVD $Ta_2O_5$ dielectric films were deposited and thermally treated to study the dielectrical characteristics of $Ta_2O_5$ film on each electrode. MIS capacitors with $Ta_2O_5$ films were electrically characterized by I-V, C-V and TDDB measurements. As a result, the capacitance of the electrode with uneven surface were increased by a factor of 1.2~1.5 and leakage current was increased compared with those of even surface. TDDB result indicates that the electrode with uneven surface has dielectrically more degraded than that of even surface. These results can be helpful as a basic research to develop new generation DRAM capacitors with $Ta_2O_5$ films.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1487-1489
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• 2001

The tantalum oxide($Ta_2O_5$) is an important material for present thin-film capacitor application owing to its high dielectric constant and thermal stability. We report dielectric property of Si(p type)/Pt/$Ta_2O_5$/Ag based MIM structure obtained by RF sputtering and annealed in vacuum environment. We have measured and researched the characteristics of C-F, C-V and EPMA. And we describe parameter dependence on sputtered condition and annealed temperature with dielectric property.