Characterization of tantalum oxy-nitrides deposited by ECR sputtering

Kato, Koji; Toyota, Hiroshi; Jin, Yoshito; Ono, Takahito

doi:10.1016/j.vacuum.2008.04.045

Cited by 26 publications

(22 citation statements)

References 12 publications

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“…These values are quite higher than 10 indicating that TaON has excellent dielectric properties. Our calculated average value of 25.68 matches well the experimental one 48. …”

supporting

confidence: 86%

First-Principles Investigation of Optoelectronic and Redox Properties of (Ta_1–xNb_x)ON Compounds for Photocatalysis

Harb

2015

J. Phys. Chem. C

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We investigate essential fundamental properties of monoclinic (Ta 1-x Nb x )ON (x = 0.0625, 0.125, 0.25, and 0.5) solid solution semiconductor materials for water splitting using first-principles computations on the basis of density functional theory (DFT) and density functional perturbation theory (DFPT) using the PBE and HSE06 functionals. The formation energies, band gaps, UVvisible optical absorption coefficients, dielectric constants, charge carrier effective masses and band edge energy positions of these compounds are evaluated. Similarly to TaON, our calculations reveal strongly 3D delocalized characters of the band edge electronic states through the crystal lattices, high dielectric constants, small hole effective masses along [001] direction and small electron effective masses along [100] direction. This leads to good exciton dissociation ability into free charge carriers, good hole mobility along [001] direction and good electron mobility along [100] direction. The main difference, however, is related to their band edge positions with respect to water redox potentials. TaON with a calculated bandgap energy of 3.0eV is predicted as a good candidate for water oxidation and O 2 evolution while the (Ta 1-x Nb x )ON materials (for 0.25 ≤ x ≤ 0.5) with calculated bandgap energies between 2.8 and 2.9 eV reveal suitable band edge positions for water oxidation and H + reduction. These results offer a grand opportunity for these compounds to be properly synthesized and tested for solar-driven overall water-splitting reactions. KeywordsNb-modified TaON, dielectric constant, charge carrier transport, band edge energy positions.

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“…These values are quite higher than 10 indicating that TaON has excellent dielectric properties. Our calculated average value of 25.68 matches well the experimental one 48. …”

supporting

confidence: 86%

First-Principles Investigation of Optoelectronic and Redox Properties of (Ta_1–xNb_x)ON Compounds for Photocatalysis

Harb

2015

J. Phys. Chem. C

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“…Our calculated diagonal components of the static dielectric tensors are reported in Table 4 [65]. In the case of Ta 3 N 5 , higher dielectric constants of 35.15, 39.68 and 53.88 are obtained along the principal crystallographic directions with an average value of 43.…”

Section: Dielectric Constant and Charge Carrier Effective Massesmentioning

confidence: 94%

Combined experimental and theoretical assessments of the lattice dynamics and optoelectronics of TaON and Ta3N5

Nurlaela

Harb

Gobbo

et al. 2015

Journal of Solid State Chemistry

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a b s t r a c tPresented herein is a detailed discussion of the properties of the lattice dynamic and optoelectronic properties of tantalum(V) oxynitride (TaON) and tantalum(V) nitride (Ta 3 N 5 ), from experimental and theoretical standpoint. The active Raman and infra red (IR) frequencies of TaON and Ta 3 N 5 were measured using confocal Raman and Fourier Transform Infrared spectroscopies (FTIR) and calculated using the linear response method within the density functional perturbation theory (DFPT). The detailed study leads to an exhaustive description of the spectra, including the symmetry of the vibrational modes. Electronic structures of these materials were computed using DFT within the range-separated hybrid HSE06 exchange-correlation formalism. Electronic and ionic contributions to the dielectric constant tensors of these materials were obtained from DFPT within the linear response method using the PBE functional. Furthermore, effective mass of photogenerated holes and electrons at the band edges of these compounds were computed from the electronic band structure obtained at the DFT/HSE06 level of theory. The results suggest that anisotropic nature in TaON and Ta 3 N 5 is present in terms of dielectric constant and effective masses.

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“…Therefore, a moderate carrier concentration that enables a relatively large volume of space charge region with respect to material bulk while still affords sufficient film conductivity is highly desirable in photoelectrodes . To validate the above discussion on the role of space charge region, the space charge layer width ( W SC ) of these four TaON photoanodes are calculated using E FB values and donor concentrations derived from Mott–Schottky plots . These four TaON photoanodes are assessed to show a 500% variation in W SC values (Table ), which agrees well with our hypothesis that a higher donor concentration will lead to a thinner space charge layer.…”

Section: Resultsmentioning

confidence: 99%

Defect Engineering in Semiconductors: Manipulating Nonstoichiometric Defects and Understanding Their Impact in Oxynitrides for Solar Energy Conversion

Feng

Huang

Fang

et al. 2019

Adv Funct Materials

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Nonstoichiometric defects, as manifested by slight deviation of elemental compositions from chemical formulas, are common yet highly important in solid materials. Oxynitrides with a relatively large O/N ratio variation are theoretically predicted to change their electronic structures and charge transport behaviors with these nonstoichiometric defects. However, little experimental effort is devoted to understanding the impact of such nonstoichiometric defects regarding varied O/N ratios in oxynitrides for solar water splitting. The main reason is the lack of suitable oxynitride research models for aforementioned nonstoichiometric defect study without interference from other factors. Using TaON as a prototypical material, finely tuned O/N ratios can dramatically influence its photoresponse. In-depth analysis further reveals a significant impact of nonstoichiometric defects (O/N ratios) on TaON's charge carrier densities, charge separation, and transport. Finally, manipulating nonstoichiometric defects of O/N ratios demonstrates its ability to control the space charge layer width and film conductivity of TaON photoanodes for high efficiency water splitting. Therefore, a fine understanding and control of nonstoichiometric defects would be highly important for future development of high efficiency oxynitrides for water splitting.

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Characterization of tantalum oxy-nitrides deposited by ECR sputtering

Cited by 26 publications

References 12 publications

First-Principles Investigation of Optoelectronic and Redox Properties of (Ta_1–xNb_x)ON Compounds for Photocatalysis

First-Principles Investigation of Optoelectronic and Redox Properties of (Ta_1–xNb_x)ON Compounds for Photocatalysis

Combined experimental and theoretical assessments of the lattice dynamics and optoelectronics of TaON and Ta3N5

Defect Engineering in Semiconductors: Manipulating Nonstoichiometric Defects and Understanding Their Impact in Oxynitrides for Solar Energy Conversion

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Characterization of tantalum oxy-nitrides deposited by ECR sputtering

Cited by 26 publications

References 12 publications

First-Principles Investigation of Optoelectronic and Redox Properties of (Ta1–xNbx)ON Compounds for Photocatalysis

First-Principles Investigation of Optoelectronic and Redox Properties of (Ta1–xNbx)ON Compounds for Photocatalysis

Combined experimental and theoretical assessments of the lattice dynamics and optoelectronics of TaON and Ta3N5

Defect Engineering in Semiconductors: Manipulating Nonstoichiometric Defects and Understanding Their Impact in Oxynitrides for Solar Energy Conversion

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Product

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About

First-Principles Investigation of Optoelectronic and Redox Properties of (Ta_1–xNb_x)ON Compounds for Photocatalysis

First-Principles Investigation of Optoelectronic and Redox Properties of (Ta_1–xNb_x)ON Compounds for Photocatalysis