Prediction of new metastable 
                $$\hbox {HfO}_{2}$$
                
                    
                                    
                        
                            HfO
                            2
                        
                    
                
             phases: toward understanding ferro- and antiferroelectric films

Barabash, S. V.

doi:10.1007/s10825-017-1077-5

Cited by 46 publications

(35 citation statements)

References 46 publications

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“…First-principles structure calculations predict that at least five polar polymorphs (with space groups Pca2 1 , Cc, Pmn2 1 , R3 and R3m) fall in an energy window possible to achieve experimentally, among which the polar o-phase (Pca2 1 ) has the least energy (64 meV/f.u.) [30,38,39]. This phase has been observed (and sometimes assumed) in polycrystalline ferroelectric layers grown via atomic layer deposition (ALD) [1,10,40,41], chemical solution deposition (CSD) [42], RF sputtering [43,44], co-evaporation and plasma assisted atomic oxygen deposition [40], as well as epitaxial layers obtained via pulsed laser deposition (PLD) [25,[33][34][35]37,45,46].…”

Section: Introductionmentioning

confidence: 99%

Guidelines for the stabilization of a polar rhombohedral phase in epitaxial Hf_0.5Zr_0.5O₂ thin films

et al. 2020

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The unconventional Si-compatible ferroelectricity in hafnia-based systems, which becomes robust only at nanoscopic sizes, has attracted a lot of interest. While a metastable polar orthorhombic (o-) phase ( Pca21) is widely regarded as the responsible phase for ferroelectricity, a higher energy polar rhombohedral (r-) phase is recently reported on epitaxial HfZrO4 (HZO) films grown on (001) SrTiO3 (R3m or R3), (0001) GaN (R3), and Si (111). Armed with results on these systems, here we report a systematic study leading towards identifying comprehensive global trends for stabilizing r-phase polymorphs in epitaxially grown HZO thin films (6 nm) on various substrates (perovskites, hexagonal and Si).

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Section: Introductionmentioning

confidence: 99%

Guidelines for the stabilization of a polar rhombohedral phase in epitaxial Hf_0.5Zr_0.5O₂ thin films

et al. 2020

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“…We assume that the isovalent replacement of Hf by Si or Zr occurs without any accompanying defect or charged state. Also, we focus on the lowest energy and most common FE phase of hafnia, which has orthorhombic symmetry

P c a 2_{1}

, and we denote “FE‐o” in the following; thus, we do not consider here other FE polymorphs recently reported .

{HfO}_{2}

has many PE phases, but here we consider only two: the common monoclinic phase, with

P 2_{1} / c

symmetry and denoted “PE‐m” in the following, which is stable at ambient conditions and constitutes the ground state of the pure compound, and the PE tetragonal polymorph with space group

P 4_{2} / n m c

and denoted “PE‐t” in the following, which has been discussed as a bridge state, leading to the stabilization of the FE‐o structure and whose relevance in this work will be made clear in the following paragraphs.…”

mentioning

confidence: 99%

“…Here

E (x)

is the energy of the

{Hf}_{1 - x} {normalA}_{x} {normalO}_{2}

compound as computed for a particular polymorph and arrangement of the A dopants; further,

E_{{HfO}_{2}}

and

E_{{AO}_{2}}

are the ground‐state energies of the pure

{HfO}_{2}

and

{AO}_{2}

materials, respectively. The PE‐m phase is considered to be the ground state of

{HfO}_{2}

and

{ZrO}_{2}

. For

{SiO}_{2}

, we use the

I \overset{false¯}{4} 2 d

structure reported in the study by Coh and Vanderbilt …”

mentioning

confidence: 99%

Effect of Dopant Ordering on the Stability of Ferroelectric Hafnia

Dutta

Aramberri

Schenk

et al. 2020

Physica Rapid Research Ltrs

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Films of all-important compound hafnia (HfO2) can be prepared in an orthorhombic ferroelectric (FE) state that is ideal for applications, e.g. in memories or negative-capacitance field-effect transistors. The origin of this FE state remains a mystery, though, as none of the proposed mechanisms for its stabilization -from surface and size effects to formation kinetics -is fully convincing. Interestingly, it is known that doping HfO2 with various cations favors the occurrence of the FE polymorph; however, existing first-principles works suggest that doping by itself is not sufficient to stabilize the polar phase over the usual non-polar monoclinic ground state. Here we use first-principles methods to reexamine this question. We consider two representative isovalent substitutional dopants, Si and Zr, and study their preferred arrangement within the HfO2 lattice. Our results reveal that small atoms like Si can adopt very stable configurations (forming layers within specific crystallographic planes) in the FE orthorhombic phase of HfO2, but comparatively less so in the non-polar monoclinic one. Further, we find that, at low concentrations, such a dopant ordering yields a FE ground state, the usual paraelectric phase becoming a higher-energy metastable polymorph. We discuss the implications of our findings, which constitute a definite step forward towards understanding ferroelectricity in HfO2.

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“…Other polymorphs of O‐fe phase such as Pbcm, and Pbca have been reported for these samples. [ 38 ] Apart from monoclinic, tetragonal, orthorhombic, and cubic phases, a rhombohedral phase was also predicted by Barabash [ 39 ] and later observed by Wei et al [ 40 ] in Hf 0.5 Zr 0.5 O 2 . Ferroelectric stacks are known to be sensitive to field cycling and to this end phenomena such as wake‐up effect and fatigue have been reported.…”

Section: Discussionmentioning

confidence: 70%

Ferroelectric Phase Content in 7 nm Hf_(1−x)Zr_xO₂ Thin Films Determined by X‐Ray‐Based Methods

Mukundan

Consiglio²,

Triyoso³

et al. 2021

Physica Status Solidi (a)

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The recent discovery of ferroelectric behavior in hafnia-based dielectrics attributed to the formation of noncentrosymmetric orthorhombic phase has opened up potential uses in numerous applications ranging from ferroelectric field effect transistors to pyroelectric energy harvesters. Herein, the relative amounts of ferroelectric orthorhombic phase (space group Pca2 1 ) in 7 nm-thick hafnia-zirconia (HZO) films of three compositions (Hf 0.2 Zr 0.8 O 2 , Hf 0.5 Zr 0.5 O 2 , and Hf 0.8 Zr 0.2 O 2 ) are reported. The ferroelectric behavior in these ultrathin HZO films prepared by atomic layer deposition (ALD) in metal-insulator-metal (MIM) stacks is verified by polarization measurements. Using grazing incidence X-ray diffraction (GIXRD) and grazing incidence-extended X-ray absorption fine structure spectroscopy (GI-EXAFS), the relative phase percentages of three key phases (monoclinic-P2 1 /c, orthorhombic-Pca2 1 , and tetragonal-P4 2 /nmc) are assessed. Among these compositions, Hf 0.5 Zr 0.5 O 2 is determined to have the highest amount of the ferroelectric phase. The monoclinic phase is found to be dominant for Hf 0.8 Zr 0.2 O 2 , whereas the tetragonal phase is found to be dominant for Hf 0.2 Zr 0.8 O 2 . Independent GI-EXAFS measurements of Hf and Zr suggest that there is no significant segregation of either oxide into a particular crystal phase. Strong agreement between the measurement methods reveals the structure-property function correlation in these ultrathin hafnia-zirconia films with greater certainty than previously achieved.

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Prediction of new metastable $$\hbox {HfO}_{2}$$ HfO 2 phases: toward understanding ferro- and antiferroelectric films

Cited by 46 publications

References 46 publications

Guidelines for the stabilization of a polar rhombohedral phase in epitaxial Hf_0.5Zr_0.5O₂ thin films

Guidelines for the stabilization of a polar rhombohedral phase in epitaxial Hf_0.5Zr_0.5O₂ thin films

Effect of Dopant Ordering on the Stability of Ferroelectric Hafnia

Ferroelectric Phase Content in 7 nm Hf_(1−x)Zr_xO₂ Thin Films Determined by X‐Ray‐Based Methods

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Prediction of new metastable $$\hbox {HfO}_{2}$$ HfO 2 phases: toward understanding ferro- and antiferroelectric films

Cited by 46 publications

References 46 publications

Guidelines for the stabilization of a polar rhombohedral phase in epitaxial Hf0.5Zr0.5O2 thin films

Guidelines for the stabilization of a polar rhombohedral phase in epitaxial Hf0.5Zr0.5O2 thin films

Effect of Dopant Ordering on the Stability of Ferroelectric Hafnia

Ferroelectric Phase Content in 7 nm Hf(1−x)ZrxO2 Thin Films Determined by X‐Ray‐Based Methods

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Guidelines for the stabilization of a polar rhombohedral phase in epitaxial Hf_0.5Zr_0.5O₂ thin films

Guidelines for the stabilization of a polar rhombohedral phase in epitaxial Hf_0.5Zr_0.5O₂ thin films

Ferroelectric Phase Content in 7 nm Hf_(1−x)Zr_xO₂ Thin Films Determined by X‐Ray‐Based Methods