Thermodynamic stability of thin ferroelectric films

Batra, Inder P.; Silverman, B. D.

doi:10.1016/0038-1098(72)91180-5

Cited by 139 publications

(91 citation statements)

References 4 publications

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“…These include the intrinsic size effect on ferroelectricity, [14][15][16] the influence of depolarizing field, 17,18 the surface tension effect, 8 and the surface bond contraction. 19 In ceramic materials, where individual crystallites are surrounded by a ferroelectric medium, the mechanical effect caused by the elastic three-dimensional ͑3D͒ clamping of crystallites may play an important role.…”

Section: Introductionmentioning

confidence: 99%

Phase states of nanocrystalline ferroelectric ceramics and their dielectric properties

Zembilgotov

Pertsev

Waser

2005

Journal of Applied Physics

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Using a nonlinear thermodynamic theory, we describe equilibrium polarization states and the macroscopic dielectric response of nanocrystalline ferroelectric ceramics with single-domain grains. The elastic clamping of individual crystallites by the surrounding material is explicitly taken into account via the introduction of a specific thermodynamic potential. Aggregate material properties are calculated with the aid of an iterative procedure based on the method of effective medium. The numerical calculations, performed for unpolarized BaTiO3 and Pb(Zr1−xTix)O3 ceramics, demonstrate that the equilibrium phase states of nanocrystalline ceramics may differ drastically from those of single crystals and coarse-grained materials. Remarkably, the theory predicts the coexistence of rhombohedral and tetragonal crystallites in nanocrystalline Pb(Zr1−xTix)O3 ceramics in a wide range of compositions and temperatures. For BaTiO3 ceramics, a mixture of rhombohedral and orthorhombic crystallites is found to be the energetically most favorable state at room temperature. The calculations also show that the dielectric properties of nanocrystalline ferroelectric ceramics may be very different from those of conventional materials due to the elastic clamping of single-domain crystallites.

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Section: Introductionmentioning

confidence: 99%

Phase states of nanocrystalline ferroelectric ceramics and their dielectric properties

Zembilgotov

Pertsev

Waser

2005

Journal of Applied Physics

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“…The driving force behind this is the large electrostatic energy penalty for a buildup of charge at the interface caused by discontinuous polarization in the normal direction. The electrostatic model proposed by Neaton and Rabe [5] to explain their first principles results for BaTiO 3 /SrTiO 3 superlattices is very similar to the electrostatic model applied to calculate the effect of the depolarization field in ultra-thin ferroelectric films with realistic electrodes [18,19,20]. Experimentally it was recently shown that the reduced polarization observed in monodomain thin PbTiO 3 can be explained by the presence of a depolarization field resulting from imperfect screening of the polarization [21].…”

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confidence: 95%

Unusual Behavior of the Ferroelectric Polarization inPbTiO3/SrTiO3Superlattices

et al. 2005

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Artificial PbTiO3/SrTiO3 superlattices were constructed using off-axis RF magnetron sputtering. X-ray diffraction and piezoelectric atomic force microscopy were used to study the evolution of the ferroelectric polarization as the ratio of PbTiO3 to SrTiO3 was changed. For PbTiO3 layer thicknesses larger than the 3-unit cells SrTiO3 thickness used in the structure, the polarization is found to be reduced as the PbTiO3 thickness is decreased. This observation confirms the primary role of the depolarization field in the polarization reduction in thin films. For the samples with ratios of PbTiO3 to SrTiO3 of less than one a surprising recovery of ferroelectricity that cannot be explained by electrostatic considerations was observed.The construction of artificial ferroelectric oxide superlattices with fine periodicity presents exciting possibilities for the development of new materials with extraordinary properties and furthermore is an ideal probe for understanding the fundamental physics of ferroelectric materials.The most studied system at present is BaTiO 3 /SrTiO 3 [1,2,3,4,5,6,7,8] In BaTiO 3 /SrTiO 3 , first principles studies [5] suggest that both the SrTiO 3 and BaTiO 3 layers are polarized such that the polarization is approximately uniform throughout the superlattice. The driving force behind this is the large electrostatic energy penalty for a buildup of charge at the interface caused by discontinuous polarization in the normal direction. The electrostatic model proposed by Neaton and Rabe [5] to explain their first principles results for BaTiO 3 /SrTiO 3 superlattices is very similar to the electrostatic model applied to calculate the effect of the depolarization field in ultra-thin ferroelectric films with realistic electrodes [18,19,20]. Experimentally it was recently shown that the reduced polarization observed in monodomain thin PbTiO 3 can be explained by the presence of a depolarization field resulting from imperfect screening of the polarization [21]. Recent work also suggests that, under certain conditions, the electrostatic energy due to depolarization fields will drive the system to form domains as observed by Fong et al. [23] and Nagarajan et al. [24]. In this letter we use PbTiO 3 /SrTiO 3 superlattices to probe the effect of a reduced ferroelectric thickness in a dielectric environment. Our data show that the behaviour observed in PbTiO 3 thin films is reproduced for PbTiO 3 layers thicker than three unit cells. However, for thinner ferroelectric layers a surprising recovery of ferroelectricity that cannot be explained by electrostatic considerations was observed.The superlattices of PbTiO 3 /SrTiO 3 were prepared on conducting 0.5% Nb doped (001) SrTiO 3 substrates using off-axis RF magnetron sputtering with conditions similar to those used for growing high quality epitaxial c-axis PbTiO 3 thin films [21]. For all the samples discussed in this paper, the SrTiO 3 thickness was fixed at three unit cells (about 12Å). At room temperature the in-plane lattice parameters of tetragonal ferroelec...

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“…In particular, due to the convenient control of polarization ( P ) orientation with applied electric field, ferroelectricity can be useful in non-volatile memory and other information processing devices. However, in these systems, the small thickness of the film gives rise to a depolarizing field (ε dep ) caused by uncompensated surface charges 4 . In the case when the top and bottom electrodes are similar, and the potential drop in the material is smaller than the band gap, ε dep is given by:…”

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confidence: 99%

Stabilization of highly polarized PbTiO3nanoscale capacitors due to in-plane symmetry breaking at the interface

et al. 2012

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Stable ferroelectric (FE) phases in nanometer-thick films would enable ultra-high density and fast FE field effect transistors (FeFETs), and the stability of ferroelectricity in ultrathin films has been under intense theoretical and experimental investigation. Here we predict, using density functional theory calculations, that the low-energy epitaxial PbTiO3 (001)/Pt interface strengthens the electrode-oxide bonds by breaking in-plane symmetry and stabilizes a ground state with enhanced polarization in sub-nanometer oxide films, with no critical-size limit. Additionally, we show that such enhancement is related to large work function differences between the P − and P + PbTiO3 surfaces, which gives rise to a net polarizing field in the oxide.

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Thermodynamic stability of thin ferroelectric films

Cited by 139 publications

References 4 publications

Phase states of nanocrystalline ferroelectric ceramics and their dielectric properties

Phase states of nanocrystalline ferroelectric ceramics and their dielectric properties

Unusual Behavior of the Ferroelectric Polarization inPbTiO3/SrTiO3Superlattices

Stabilization of highly polarized PbTiO3nanoscale capacitors due to in-plane symmetry breaking at the interface

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