<i>Ab initio</i> study on the size effect of symmetric and asymmetric ferroelectric tunnel junctions: A comprehensive picture with regard to the details of electrode/ferroelectric interfaces

Chen, W. J.; Zheng, Yue; Luo, Xin; Wang, Biao; Woo, C.H.

doi:10.1063/1.4817656

Cited by 25 publications

(20 citation statements)

References 55 publications

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“…Figure 1(f) shows that the relaxations of ions and electrons at the interface induce interface dipoles even in the paraelectric state. Besides, the dipoles are perpendicular to the corresponding interfaces and point to opposite directions at two interfaces, which are consistent with previous calculations [14,29]. The antisymmetric interface dipoles are attributed to the antisymmetric rumpling of atoms at the interfaces of the electrode-ferroelectrics-electrode multilayer.…”

Section: B Effect Of the Ferroelectric-electrode Interface On The Posupporting

confidence: 91%

Disappearance of ferroelectric critical thickness in epitaxial ultrathinBaZrO3films

Zhang

Shimada

et al. 2014

Phys. Rev. B

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The intrinsic critical ferroelectric thickness of epitaxial ultrathin capacitors of incipient ferroelectric BaZrO 3 (BZO) films with realistic SrRuO 3 (SRO) electrodes is investigated by first-principles calculations based on density functional theory. We reveal that polarization can stably exist even in one-unit-cell thick BZO films, i.e., absence of critical thickness, whereas the widely investigated proper ferroelectrics like BaTiO 3 and SrTiO 3 films have no polarization. The influences of realistic ferroelectric-electrode interface and misfit strain on the ionic and electronic structures of the BZO-SRO thin film system have been examined under the short-circuited boundary condition. It is found that the ionic polarization of conductive SRO electrodes can effectively strengthen the screening of bound charges at the interface, which greatly reduces the depolarization field in the BZO films. Furthermore, the epitaxial misfit strain remarkably enhances the polarization through the enhancement of hybridization of Zr and O electron orbitals, resulting in the disappearance of ferroelectric critical thickness. Our findings are beyond the critical thickness of proper ferroelectrics and are thus promising for future nanometer-scale ferroelectric device such as high-density ferroelectric memory.

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Section: B Effect Of the Ferroelectric-electrode Interface On The Posupporting

confidence: 91%

Disappearance of ferroelectric critical thickness in epitaxial ultrathinBaZrO3films

Zhang

Shimada

et al. 2014

Phys. Rev. B

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“…Also, an abnormal enhancement of ferroelectricity due to bonding at the Pt 2 /BaO interface has been predicted. However, on the grounds of the analysis and results presented in [45], the findings reported in [48] may be affected by the shortcomings inherent to LDA.…”

Section: Introductionmentioning

confidence: 94%

“…At the interface with a ferroelectric the polar distortions are perturbed, the local strain, bonding across the interface and the built-in electric field promote charge transfers and space charge build-up. In turn, these effects impact on the electronic structure, inducing relative shifts of the energy levels, modifications of band gap values, metal-induced band gap states (MIGS) and interfacial band bending effects [7,[44][45][46][47][48]. The band alignment scheme results as an effect of entangled microscopic mechanisms and plays a major role in setting the operating conditions of practical junctions [49,50].…”

Section: Introductionmentioning

confidence: 99%

“…Ferroelectric capacitors with asymmetric interfaces have been investigated with the expectation that asymmetry may furnish an enhanced device functionality comparing to the symmetric realizations (see [48] and the references cited therein). The degeneracy of polarization states in symmetric geometries is broken in asymmetric configurations and hence size effects may determine distinct states for forward-backward polarization.…”

Section: Introductionmentioning

confidence: 99%

“…The degeneracy of polarization states in symmetric geometries is broken in asymmetric configurations and hence size effects may determine distinct states for forward-backward polarization. Following this line of research, Chen et al [48], carried out a detailed study within LDA on the size effect in ferroelectric BaTiO 3 tunnel junctions with metal Pt and/or oxide SrRuO 3 electrodes, considering the four possible types of electrode/ferroelectric interfaces. They found a significant dependence of the ferroelectric stability of a tunnel junction on the type and combination of the two interfaces.…”

Section: Introductionmentioning

confidence: 99%

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Designing functional ferroelectric interfaces from first-principles: dipoles and band bending at oxide heterojunctions

et al. 2019

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The fundamental phenomena at ferroelectric interfaces have been the subject of thorough theoretical and computational studies due to their usefulness in a large variety of emergent electronic devices, solar cells and catalysts. Ferroelectricity determines interface band-bending and shifts in electron energies, which can be beneficial or detrimental to device performance. However, the underlying mechanisms are still the subject of debate and investigation, as a deeper understanding of the electrochemistry is required to develop bona fide design principles for functional ferroelectric surfaces and interfaces. Here, using first principles calculations within the GGA+U formalism, we investigate the problem of band alignment in non-defective, asymmetric SrRuO 3 /PbTiO 3 /SrRuO 3 capacitors with ultra-thin ferroelectric layers. The effects of the dielectric size on the polar distortion stability and interface-specific properties are analyzed. It is shown that the critical size of the dielectric for polarization switching is 2 nm » (5 PbTiO 3 u.c.). Below this limit there is no bulk-like region in the dielectric, the space charge accumulated at interfaces leads to the presence of gap states in the whole PbTiO 3 layer and ferroelectricity vanishes. We draw the band alignment diagrams as given by the band line-up and band structure terms, as well as by taking Ti 3s semi-core states as reference. In the ferroelectric structures, both approaches predict a strong effect of band-bending on the type of contact, Schottky or Ohmic, at the asymmetric interfaces. The effect of interface states on the interface dipole amplitude and band alignment is discussed.

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First‐Principles Calculations on Ferroelectrics for Energy Applications

Jiang

Chen

Zheng

2018

Ferroelectric Materials for Energy Applications

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Ab initio study on the size effect of symmetric and asymmetric ferroelectric tunnel junctions: A comprehensive picture with regard to the details of electrode/ferroelectric interfaces

Cited by 25 publications

References 55 publications

Disappearance of ferroelectric critical thickness in epitaxial ultrathinBaZrO3films

Disappearance of ferroelectric critical thickness in epitaxial ultrathinBaZrO3films

Designing functional ferroelectric interfaces from first-principles: dipoles and band bending at oxide heterojunctions

First‐Principles Calculations on Ferroelectrics for Energy Applications

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