• Journal of Powder Materials
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• v.25 no.5
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• pp.390-394
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• 2018

Metallic tantalum powder is manufactured by reducing tantalum oxide ($Ta_2O_5$) with magnesium gas at 1,073-1,223 K in a reactor under argon gas. The high thermodynamic stability of magnesium oxide makes the reduction reaction from tantalum oxide into tantalum powder possible. The microstructure after the reduction reaction has the form of a mixture of tantalum and magnesium oxide, and the latter could be entirely eliminated by dissolving in weak hydrochloric acid. The powder size in SEM microstructure for the tantalum powder increases after acid leaching in the range of 50-300 nm, and its internal crystallite sizes are observed to be 11.5 to 24.7 nm with increasing reduction temperatures. Moreover, the optimized reduction temperature is found to be 1,173 K as the minimum oxygen concentration is approximately 1.3 wt.%.

• Journal of information and communication convergence engineering
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• v.8 no.4
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• pp.453-456
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• 2010

Tantalum oxide ($Ta_2O_5$) films are of considerable interest for a range of application, including optical waveguide devices, high temperature resistors, and oxygen sensors. In this paper, we establish an anode oxidation process of tantalum thin film. The voltage drop in the electrolyte is affected not in voltage change but in current change. If the voltage drop in the electrolyte is same with cathode oxidation voltage, the current changes logarithmically in proportion to the voltage drop in interface of tantalum oxide and electrolyte. As a result of the measurement on the electrical property of tantalum oxide thin film, when the thickness of the insulator film is $1500{\AA}$, the breakdown voltage is 350volts and dielectric constant is 29.

• Journal of the Korean Ceramic Society
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• v.28 no.6
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• pp.443-450
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• 1991

Microstructures of tantalum oxide, anodic-oxidized in oxalic acid, are shown to be related to voltage-time characteristics during formation reaction. It is observed that a crystalline phase transformed from an amorphous phase is recrystallized in the presence of the high electric field within the film, and this recrystallized film has a very porous microstructure. From the results of the XRD, the nonlinearity observed after the first spark voltage is recognized to be due to the local crystallization.

• ETRI Journal
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• v.13 no.2
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• pp.21-27
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• 1991

Effects of annealing on the dielectric properties and microstructures of thin tantalum oxide film(25nm) deposited on p-type Si substrate with rf reactive magnetron sputtering were investigated. The leakage current density was remarkably reduced from $10^-8$ to $10^-12$ A/$\mum^2$at the electric field of 2MV/cm after rapid thermal annealing(RTA) in $O_2$at $1000^{\circ}C$, while little leakage reduction was observed after furnace annealing in $O_2$ at $500^{\circ}C$. The structural changes of thin tantalum oxide film after annealing were examined using high resolution electron microscope(HREM). The results of HREM show that substantial reduction in the leakage current density after the RTA in $O_2$ can be attributed to crystallization and reoxidation of the thin amorphous tantalum oxide film.

• Proceedings of the Materials Research Society of Korea Conference
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• 1992.05b
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• pp.151-151
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• 1992

• Journal of Electrochemical Science and Technology
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• v.4 no.4
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• pp.163-170
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• 2013

Tantalum anodic oxide film was prepared in citric acid solution of various concentrations and the prepared Ta anodic oxide film was characterized by various electrochemical techniques and X-ray photoelectron spectroscopy (XPS). The prepared Ta anodic oxide film showed typical n-type semiconducting properties and the dielectric properties were strongly dependent on the citric acid concentration. The variation of electrochemical and electronic properties was explained in terms of electrolyte anion incorporation into the anodic oxide film, which was supported by XPS measurements.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.3
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• pp.87-95
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• 1992

The electrical characteristics of Al/TaS12TOS15T/SiOS12T/Si metal insulator-semiconductor (MIS) capacitors were studied. Tantalum pentoxide thin films on SiOS12T/p-Si substrate have been prepared by thermal oxidation at 450-$600^{\circ}C$ of sputter deposited tantalum films. Composition and structures of the tantalum oxide films were examined by AES and XRD. From the C-V analysis, dielectric constant of TaS12TOS15T which were oxidized at 55$0^{\circ}C$ for 1h in OS12T were 18-23, the value depending on the oxidation and annealing temperature. The leakage current density was found to be about 10S0-10T-10S0-9T A/cmS02T at an applied electric field of 1 MV/cm. The dielectric breakdown strength of the tantalum oxide films annealed at 100$0^{\circ}C$ were in the range from 2.5MV/cm to 2.8 MV/cm.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.122.1-122.1
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• 2015

The dependence of electronic properties and local structure of tantalum oxide thin film on oxygen deficiency have been investigated by means of X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and X-ray absorption spectroscopy (XAS). The XPS results showed that the oxygen flow rate change results in the appearance of features in the Ta 4f at the binding energies of 23.2 eV, 24.4 eV, 25.8, and 27.3 eV whose peaks are attributed to Ta1+, Ta2+, Ta3+, Ta4+, and Ta5+, respectively. The presence of nonstoichiometric state from tantalum oxide (TaOx) thin films could be generated by the oxygen vacancies. The REELS spectra suggested the decrease of band gap for tantalum oxide thin films with increasing oxygen deficiency. In addition, XAS spectra manifested both the increase of coordination number of the first Ta-O shell and a considerable reduction of the Ta-O bond distance with the decrease of oxygen deficiency.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.398-398
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• 2013

The electronic properties and the local structure of tantalum oxide thin film with variation of oxygen flow rate ranging from 9.5 to 16 sccm (standard cubic centimeters per minute) have been investigated by X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and X-ray absorption spectroscopy (XAS). The XPS results show that the Ta4f spectrum for all films consist of the strong spin-orbit doublet $Ta4f_{7/2}$ and $Ta4f_{5/2}$ with splitting of 1.9 eV. The oxygen flow rate of the film results in the appearance of new features in the Ta4f at binding energies of 23.2 eV, 24.4 eV, 25.8, and 27.3 eV, these peaks attribute to $Ta^{1+}$, $Ta^{2+}$, $Ta^{4+}$/$Ta^{2+}$, and $Ta^{5+}$, respectively. Thus, the presence of non-stoichiometric state from tantalum oxide ($TaO_x$) thin films could be generated by the oxygen vacancies. The REELS spectra suggest the decrease of band gap for tantalum oxide thin films with increasing the oxygen flow rate. The absorption coefficient ${\mu}$ and its fine structure were extracted from the fluorescence mode of extended X-ray absorption fine structure (EXAFS) spectra. In addition, bond distances (r), coordination numbers (N) and Debye-Waller factors (${\sigma}^2$) each film were determined by a detailed of EXAFS data analysis. EXAFS spectrapresent both the increase of coordination number of the first Ta-O shell and a considerable reduction of the Ta-O bond distance with the increase of oxygen flow rate.

• Journal of Powder Materials
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• v.10 no.4
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• pp.255-261
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• 2003

Ultrafine TaC-5%Co composite powders were synthesized by spray conversion process using tantalum oxalate solution and cobalt nitrate hexahydrate(Co($(NO_3)_2$ . 6$H_2O$). The phase of Ta-Co oxide powders had amorphous structures after calcination below 50$0^{\circ}C$ and changed $Ta_2O_5$, $TaO_2$ and $CoTa_2O_6$ phase by heating above $600^{\circ}C$. The calcined Ta-Co oxide powders were spherical agglomerates consisted of ultrafine primary particles <50 nm in size. By carbothermal reaction, the TaC phase began to form from 90$0^{\circ}C$. The complete formation of TaC could be achieved at 105$0^{\circ}C$ for 6 hours. The observed size of TaC-Co composite powders by TEM was smaller than 200 nm.