Tantalum doping in HfO<sub>2</sub>: orthorhombic phase formation at ambient conditions and change in path of pressure-induced structural evolution

Pathak, S.; Das, P.; Sahu, Manjulata; Pandey, Kaushlendra; Mandal, Guruprasad; Patkare, Geeta R.

doi:10.1080/08957959.2020.1765338

Cited by 3 publications

(1 citation statement)

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“…Recently, Pathak et al . reported that the transformation from m‐HfO 2 to o‐HfO 2 under the ambient condition took place by doping at least 1 mol% Ta 59 , from which we could deduce that the doping effect of Ta and Nb in Hf‐containing binary carbides promotes the monoclinic‐orthorhombic transition of HfO 2 at ambient pressure during the oxidation process at 800–1200°C, while this mechanism needs further exploration. From the logarithmic XRD patterns in Figure 9, o‐HfO 2 increases with oxidation temperatures for both oxidized (Hf 0.5 Nb 0.5 )C and (Hf 0.5 Ta 0.5 )C, implying a boost for the m‐o transformation of HfO 2 .…”

Section: Resultsmentioning

confidence: 83%

Low‐temperature synthesis and oxidation resistance of random combination of Hf, Nb, and Ta carbides microcuboids

Geng

Huang

et al. 2022

J Am Ceram Soc.

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Based on the dissolution‐precipitation mechanism, this article successfully synthesized binary and ternary transition metal carbide microcuboids with random combinations of Hf, Nb, and Ta by annealing monocarbides/cobalt powders. Accelerated mass transport rate through the flow of molten alloys (Co‐Hf‐Nb‐Ta) instead of slow solid diffusion made the low‐temperature pressureless sintering technique (1500°C) a reality. Furthermore, the equilibrium morphology was driven by the gradient Gibbs potential of carbides induced by the different local curvature of powders and anisotropic interfacial energy. (Hf0.5Ta0.5)C possessed the optimal oxidation resistance among all mentioned carbides, even competed with (Hf1/3Nb1/3Ta1/3)C. During the isothermal oxidation at 800∼1200°C, the doping of Nb and Ta in carbides assisted the monoclinic‐orthorhombic HfO2 transition at ambient pressure, besides, TaC can also restrain the orthorhombic‐monoclinic transition of Nb2O5. Moreover, oxidation kinetics parameters concluded that the addition of HfC and TaC contributed to the decreasing reaction order and the increasing activation energy, respectively.

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Section: Resultsmentioning

confidence: 83%

Low‐temperature synthesis and oxidation resistance of random combination of Hf, Nb, and Ta carbides microcuboids

Geng

Huang

et al. 2022

J Am Ceram Soc.

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Structure evolution, bandgap, and dielectric function in La-doped hafnium oxide thin layer subjected to swift Xe ion irradiation

Suvorova

Уваров

Архарова

et al. 2020

Journal of Applied Physics

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High-resolution transmission electron microscopy, electron diffraction, and electron energy-loss spectroscopy provide information on the structural evolution, dielectric function, and bandgap values of nanocrystalline 10 nm thick lanthanum doped hafnia (La:HfO2) layers in TiN/La:HfO2/TiN/SiO2/Si irradiated with 24, 46, 72, and 160 MeV (0.2–1.2 MeV/u) Xe ions. Swift heavy Xe ions were expected to create significant atomic rearrangements when passed through a solid losing energy mainly through electronic excitation and ionization of the target atoms. Local heating and subsequent rapid cooling in the region around the ion track can lead to re-solidification with the formation of a new stable crystalline phase, and direct crystal-to-crystal transformations are possible. The structure evolution of hafnia nanocrystals from the orthorhombic Pbcm in the pristine layer to the tetragonal P42/nmc phase in the 160 MeV Xe ion irradiated layer was observed. The mixture of tetragonal and orthorhombic phases was found in samples irradiated with ions of intermediate energies. Textured hafnia layers were formed as a result of ion irradiation. The changes in plasmon line shape and the blueshift of the plasmon energy-loss peak from 14.9 eV in the pristine layer to 15.4 eV in 46 MeV and 15.9 eV in 160 MeV Xe ion irradiated hafnia reflect structural transformations, the increase in the Hf coordination number, and crystal orientations. Valence-electron energy-loss spectroscopy measurements showed a slight increase in the bandgap value from 6.1 eV in the pristine sample to 6.2 eV and 6.3 eV in irradiated samples with 46 and 160 MeV Xe ions, respectively, and dielectric functions changed insignificantly in irradiated hafnia layers.

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Large remanent polarization in Ta-doped HfO2 thin films by reactive sputtering

Luo

Kang

Song

et al. 2021

Applied Physics Letters

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Ta-doped HfO2 thin films grown on Pt/Ti/SiO2/Si by reactive sputtering possess strong ferroelectric properties, as detected by corresponding polarization vs electric field measurement and mesoscopic piezoresponse force microscopy. Capacitance/current-electric field curves are used to reveal the substances with ferroelectric properties in the thin films. The ferroelectricity of Ta-doped HfO2 is influenced by Ta contents. The remanent polarization Pr can reach ∼53 μC/cm2 by optimizing the Ta percentage. X-ray diffraction and Raman scattering analyses indicate only the presence of monoclinic phase peaks in undoped HfO2 thin films, while Ta doping promotes the formation of the ferroelectric phase (orthorhombic Pca21). X-ray photoelectron spectroscopy demonstrates that the incorporation of Ta5+ within the HfO2 lattice boosts the ferroelectric properties. A polydomain structure is observed on the bare surface of 16% Ta-doped HfO2. Moreover, the switching behavior of the domain is explored by applying an external voltage, demonstrating the potential for storage device applications.

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Tantalum doping in HfO₂: orthorhombic phase formation at ambient conditions and change in path of pressure-induced structural evolution

Cited by 3 publications

References 40 publications

Low‐temperature synthesis and oxidation resistance of random combination of Hf, Nb, and Ta carbides microcuboids

Low‐temperature synthesis and oxidation resistance of random combination of Hf, Nb, and Ta carbides microcuboids

Structure evolution, bandgap, and dielectric function in La-doped hafnium oxide thin layer subjected to swift Xe ion irradiation

Large remanent polarization in Ta-doped HfO2 thin films by reactive sputtering

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Tantalum doping in HfO2: orthorhombic phase formation at ambient conditions and change in path of pressure-induced structural evolution

Cited by 3 publications

References 40 publications

Low‐temperature synthesis and oxidation resistance of random combination of Hf, Nb, and Ta carbides microcuboids

Low‐temperature synthesis and oxidation resistance of random combination of Hf, Nb, and Ta carbides microcuboids

Structure evolution, bandgap, and dielectric function in La-doped hafnium oxide thin layer subjected to swift Xe ion irradiation

Large remanent polarization in Ta-doped HfO2 thin films by reactive sputtering

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Tantalum doping in HfO₂: orthorhombic phase formation at ambient conditions and change in path of pressure-induced structural evolution