Hafnia and hafnia-toughened ceramics

Wang, J.; Li, H. P.; Stevens, R.

doi:10.1007/bf00541601

Cited by 545 publications

(371 citation statements)

References 101 publications

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“…Using an isotropic pressure constraint the phase stability is determined by the Gibbs energy G as (3) with the pressure p and the volume V. Diamond-anvil cells have been used to determine pressure driven phase transformations experimentally. For HfO2 36,60 and ZrO2 38,54 , the phase transformation from the m-phase to an orthorhombic phase has been found between 4-12 GPa.…”

Section: Strain and Stress G Ibbs Energymentioning

confidence: 99%

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The origin of ferroelectricity in Hf1−xZrxO2: A computational investigation and a surface energy model

Materlik

Kuenneth

Kersch

2015

Journal of Applied Physics

691

684

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The structural, thermal, and dielectric properties of the ferroelectric phase of HfO2, ZrO2 and Hf0.5Zr0.5O2 (HZO) are investigated with carefully validated density functional computations.We find, that the free bulk energy of the ferroelectric orthorhombic Pca21 phase is unfavorable compared to the monoclinic P21/c and the orthorhombic Pbca phase for all investigated stoichiometries in the HfχZr1-χO2 system. To explain the existence of the ferroelectric phase in nanoscale thin films we explore the Gibbs / Helmholtz free energies as a function of stress and film strain and find them unlikely to become minimal in HZO films for technological relevant conditions. To assess the contribution of surface energy to the phase stability we parameterize a model, interpolating between existing data, and find the Helmholtz free energy of ferroelectric grains minimal for a range of size and stoichiometry. From the model we predict undoped HfO2 to be ferroelectric for a grain size of about 4 nm and epitaxial HZO below 5 nm.Furthermore we calculate the strength of an applied electric field necessary to cause the

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Section: Strain and Stress G Ibbs Energymentioning

confidence: 99%

“…The recent discovery of ferroelectricity in HfO2 and ZrO2 based high-k materials 1,2 surprised since this material class was extensively studied for decades 3,4 . Similar to the classical perovskites, the origin of the ferroelectricity is most likely a non-centrosymmetric polar crystal phase which is stable under certain conditions.…”

Section: Introductionmentioning

confidence: 99%

The origin of ferroelectricity in Hf1−xZrxO2: A computational investigation and a surface energy model

Materlik

Kuenneth

Kersch

2015

Journal of Applied Physics

691

684

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“…7,8 Furthermore, HfO 2 serves as an excellent protective coating due to its thermal stability and hardness. 9,10 Determination of stable surface structures of materials is required for the ab initio prediction of material properties as the relative stability of the surfaces will affect the orientations and sizes of crystallites, which in turn affect materials properties. This is especially true for the prediction of surface properties such as surface reactivity.…”

Section: Introductionmentioning

confidence: 99%

First-principles calculations of structural and electronic properties of monoclinic hafnia surfaces

2006

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We have carried out a systematic theoretical study of the surfaces of monoclinic hafnia ͑HfO 2 ͒ using plane waves and density functional theory based on the generalized gradient approximation. The fully relaxed structures of the bulk phases of HfO 2 are found to be in excellent agreement with experimental data, the monoclinic phase being the most stable. Simulations of the monoclinic phase surfaces indicate a large relaxation which reduces the total surface energy of all nine faces considered by between 23% and 36%, with a strong correlation between the unrelaxed and relaxed surface energies. Our calculations predict that the ͑111͒ and ͑111͒ faces of the monoclinic phase have the lowest surface energies and are hence the most stable faces. An analysis of the total and partial electronic density of states of bulk monoclinic HfO 2 reveals that the outer valence band significantly mixes the O 2p and Hf 5d atomic states indicating some covalency of the Hf-O bonds. The total density and partial density of states of the monoclinic surfaces exhibit a surface state corresponding to the surface O 2s states in the inner valence band region.

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“…It is therefore desirable to develop liftoff processes for dielectrics similar to those used for metallization. High quality dielectric films patterned by liftoff would be of great value not only in the semiconductor industry, but also in optical applications [8,9], as catalysts [10,11], and as protective coatings [12,13].…”

mentioning

confidence: 99%

Low-temperature atomic-layer-deposition lift-off method for microelectronic and nanoelectronic applications

Biercuk

Monsma

Marcus

et al. 2003

Applied Physics Letters

181

142

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We report a novel method for depositing patterned dielectric layers with submicron features using atomic layer deposition (ALD). The patterned films are superior to sputtered or evaporated films in continuity, smoothness, conformality, and minimum feature size. Films were deposited at 100-150 C using several different precursors and patterned using either PMMA or photoresist. The low deposition temperature permits uniform film growth without significant outgassing or hardbaking of resist layers. A liftoff technique presented here gives sharp step edges with edge roughness as low as 10 nm. We also measure dielectric constants (k) and breakdown fields for the high-k materials aluminum oxide (k ~ 8-9), hafnium oxide (k ~ 16-19) and zirconium oxide (k 20-29), grown under similar low temperature conditions.

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Hafnia and hafnia-toughened ceramics

Cited by 545 publications

References 101 publications

The origin of ferroelectricity in Hf1−xZrxO2: A computational investigation and a surface energy model

The origin of ferroelectricity in Hf1−xZrxO2: A computational investigation and a surface energy model

First-principles calculations of structural and electronic properties of monoclinic hafnia surfaces

Low-temperature atomic-layer-deposition lift-off method for microelectronic and nanoelectronic applications

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