Experimental evidence of the size effect in thin ferroelectric films

Vendik, O. G.; Zubko, S. P.; Ter-Martirosayn, Leon T.

doi:10.1063/1.121715

Cited by 78 publications

(36 citation statements)

References 8 publications

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“…(ii) A thin parasitic interfacial layer, which has a small capacitance component, acts electrically in series with the rest of the film and reduces the effective dielectric constant and remanent polarisation in the system [225,226,228,238,241,243]. The physics of the ferroelectriceelectrode boundary (such as intrinsic surface polarisation effects [237,243], depolarisation fields due to incomplete screening by the electrodes [240], intrinsic suppression of polarisation at the electrode [239]) or some heteroepitaxial induced effects (like oxygen depletion zones [244], local diffusion of electrode material onto the ferroelectric [236], lattice mismatched induced ion vacancy formation [227], chemically different surface phase or surface contamination [220,223,237]) have indeed been proposed for the peak broadening effect. (iii) In the dead layer model, recently proposed by Sinnamon et al for films with columnar microstructure, dead layers at the grain boundaries rather than at the ferroelectrice electrode interface were considered [234,235].…”

Section: Thickness Dependencementioning

confidence: 99%

Epitaxial growth of ferroelectric oxide films

Schwarzkopf

Fornari

2006

Progress in Crystal Growth and Characterization of Materials

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Section: Thickness Dependencementioning

confidence: 99%

Epitaxial growth of ferroelectric oxide films

Schwarzkopf

Fornari

2006

Progress in Crystal Growth and Characterization of Materials

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“…9 and 12, we use values of 100 nm for ␣ 1 and ␣ 2 , and L, the thickness of the film. With a correlation coefficient D * of the order of ϳ10 −9 ͑SI units͒, 9,19,20 the value of the flexoelectric coefficient is ͑␥ − ͒ = 0.1ϫ 10 −9 m 3 C −1 . We note that parameters for the penetration depth of the strain ͑␣ 1 and ␣ 2 ͒ are very important for the polarization profiles in ferroelectric thin films, through which properties of the thin film may then be controlled experimentally.…”

Section: ͑5͒mentioning

confidence: 99%

Effects of strain gradient on charge offsets and pyroelectric properties of ferroelectric thin films

Zheng

Wang

Woo

2006

Applied Physics Letters

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The Landau-Ginzburg-Devonshire theory is used to study the effects of the strain gradient due to the epitaxial stresses in ferroelectric thin films sandwiched between two different substrates. The polarization in the film is found to be nonuniform, resulting in charge offsets and an asymmetric hysteresis response with characteristics similar to those in compositionally graded ferroelectric materials. The authors' results suggest that the charge offset and pyroelectric effects can also be produced with effect of the strain gradient in film. In addition, such effects are found to be sensitive to an applied load. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2335369͔Functionally graded ferroelectrics in the form of either bulk or thin films possess properties 1-8 different from those of homogeneous ferroelectrics. The distribution of the polarization in graded ferroelectric devices is asymmetric and graded, and there is a translation of the hysteresis loop along the polarization axis with an attendant charge offset. As a result of this asymmetry, other properties such as the effective pyroelectric response, temperature dependence of the dielectric behavior, etc., 1,3 are also affected.At the same time, a strain gradient in a uniform ferroelectric thin film may also produce similar effects. [9][10][11][12][13][14] In this letter, we report on our investigation of the effects of the strain gradient caused by the epitaxial stresses in ferroelectric thin films ͑FTFs͒ sandwiched between two different substrates. Following the Landau-Ginzburg-Devonshire ͑LGD͒ theory, a general model that includes effects of flexoelectricity and stress gradient is formulated and applied.The thickness of the FTF is L, and the thicknesses of the rigid substrates are assumed to be much larger than L, so that the system can be considered to remain flat. The polarization P due to the eigenstrain of the ferroelectric transformation ͑simply called self-polarization͒ is assumed to be perpendicular to the film surface and is homogeneous on the x-y plane. Using the LGD theory and the Legendre transformation, the total free energy per unit area of the film can be written as: 4,9,10,15where A, B, and C are the expansion coefficients of the Landau free energy and D can be approximated as 2 · ͉A͑T − T c0 ͉͒, where T c0 is the Curie-Weiss temperature of the bulk material and is the characteristic length along which the polarization varies. 1 ␥ and are the direct and converse flexoelectric coefficients, respectively. 9,10 Q 12 is the electrostrictive coefficient describing the coupling between the mechanical deformation and the self-polarization. P 0 and P L are the polarizations, and ␦ 0 and ␦ L are the extrapolation lengths at the upper and lower surfaces, respectively. s ij is the elastic compliance tensor. E d ͑z͒ is the depolarization field and E ext ͑z͒ is the external field, which have been defined in Refs. 1, 3, and 4. u is the total biaxial in-plane residual strain in the thin film. x 1 = x 2 = x 0 is the transformation strain given by x...

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“…[7][8][9][10] However, no definitive origin for the proposed dielectric "dead-layer" has yet been discovered. Some researchers have suggested that it is associated with fundamental interface physics, [10][11][12][13][14][15] but there are a great number of other hypotheses which are capable of generating series capacitance behavior: strain gradients; 16,17 physical layers of low permittivity either adjacent to the electrodes in the capacitor, 18,19 or at grain boundaries in the ferroelectric; 20 parasitic capacitance associated with the finite charge screening lengths in nonideal electrodes; [21][22][23][24] even subtleties in device asymmetry. 25 Such a variety of possible explanations for permittivity suppression makes for interesting and active debate, but it equally leads to a great deal of confusion and uncertainty, and does not clearly define how detrimental effects on permittivity might be avoided.…”

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confidence: 99%

Size effects on thin film ferroelectrics: Experiments on isolated single crystal sheets

Chang

McMillen

Morrison

et al. 2008

Applied Physics Letters

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Thin lamellae were cut from bulk single crystal BaTiO3 using a focused ion beam microscope. They were then removed and transferred onto single crystal MgO substrates, so that their functional properties could be measured independent of the original host bulk ferroelectric. The temperature dependence of the capacitance of these isolated single crystal films was found to be strongly bulklike, demonstrating a sharp Curie anomaly, as well as Curie–Weiss behavior. In addition, the sudden change in the remanent polarization as a function of temperature at TC was characteristic of a first order phase change. The work represents a dramatic improvement on that previously published by Saad et al. [J. Phys.: Condens. Matter 16, L451 (2004)], as critical shortcomings in the original specimen geometry, involving potential signal contributions from bulk BaTiO3, have now been obviated. That the functional properties of single crystal thin film lamellae are comparable to bulk, and not like those of conventionally deposited heterogeneous thin film systems, has therefore been confirmed.

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Experimental evidence of the size effect in thin ferroelectric films

Abstract: Ferroelectricity in sol-gel derived Ba 0.8 Sr 0.2 TiO 3 thin films using a highly diluted precursor solution

Cited by 78 publications

References 8 publications

Epitaxial growth of ferroelectric oxide films

Epitaxial growth of ferroelectric oxide films

Effects of strain gradient on charge offsets and pyroelectric properties of ferroelectric thin films

Size effects on thin film ferroelectrics: Experiments on isolated single crystal sheets

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