Depletion and depolarizing effects in ferroelectric thin films and their manifestations in switching and fatigue

Tagantsev, A. K.; Pawlaczyk, Cz.; Brooks, Keith G.; Landivar, M.; Colla, Enrico; Setter, N.

doi:10.1080/10584589508019374

Cited by 51 publications

(31 citation statements)

References 14 publications

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“…4, where in steady state, the dopants segregate along a domain wall in an asymmetric manner creating a defect dipole. Recent simultaneous AFM-PFM measurements of emerging 90 domain walls in BaTiO 3 show that the physical width is significantly smaller (over 7 times) than the piezoelectric width consistent with longrange electrostatic interactions [21]. Further, the decoration of the domain wall with defects is consistent with experimental observations of Shilo et al [22] and provides a mechanism for the domain wall to have a memory of its location during annealing.…”

Section: Prl 95 247603 (2005) P H Y S I C a L R E V I E W L E T T E supporting

confidence: 69%

“…Consequently, one has bandbending and depletion layers at electrodes and charge layer formation at domain walls, which in turn affect the polarization distribution. These in turn contribute to fatigue and domain-wall pinning.Recent efforts have sought to augment the DGL theory for these effects [3]. However, they assume a priori the depletion layer and space-charge distribution and calculate the resulting polarization distribution, or vice versa.…”

mentioning

confidence: 99%

“…Recent efforts have sought to augment the DGL theory for these effects [3]. However, they assume a priori the depletion layer and space-charge distribution and calculate the resulting polarization distribution, or vice versa.…”

mentioning

confidence: 99%

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Depletion Layers and Domain Walls in Semiconducting Ferroelectric Thin Films

2005

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Commonly used ferroelectric perovskites are also wide-band-gap semiconductors. In such materials, the polarization and the space-charge distribution are intimately coupled, and this Letter studies them simultaneously with no a priori ansatz on either. In particular, we study the structure of domain walls and the depletion layers that form at the metal-ferroelectric interfaces. We find the coupling between polarization and space charges leads to the formation of charge double layers at the 90 domain walls, which, like the depletion layers, are also decorated by defects like oxygen vacancies. In contrast, the 180 domain walls do not interact with the defects or space charges. Implications of these results to domain switching and fatigue in ferroelectric devices are discussed. DOI: 10.1103/PhysRevLett.95.247603 PACS numbers: 77.80.Dj, 73.40.ÿc, 75.60.Ch Ferroelectric perovskites that are widely used as actuators, sensors, and memories have classically been modeled as insulators following the Devonshire-Ginsburg-Landau (DGL) theory [1]. These materials, however, are also wideband-gap semiconductors [2]. Consequently, one has bandbending and depletion layers at electrodes and charge layer formation at domain walls, which in turn affect the polarization distribution. These in turn contribute to fatigue and domain-wall pinning.Recent efforts have sought to augment the DGL theory for these effects [3]. However, they assume a priori the depletion layer and space-charge distribution and calculate the resulting polarization distribution, or vice versa. There have also been ab initio studies of the electronic band structure and atomistic studies of defects [4 -6]. However, they provide limited information at the device scale due to enormous computational effort required to handle realistic length scales and geometries. This Letter provides a comprehensive presentation of a semiconducting ferroelectric at the device scale with no a priori assumptions on the polarization or space charge.We focus on the [001]-polarized tetragonal phase of BaTiO 3 to be specific, though many of our findings are generic. This well-studied material displays both 180 and 90 domain walls. Oxygen vacancies are a common defect and they act as donors [6,7]. We focus on the parallel-plate capacitor geometry (electrode-ferroelectric-electrode), which is the building block of many devices. Our results show the formation of depletion layers and the alteration of the polarization near electrodes, reveal some essential differences between 180 and 90 domain walls, show the redistribution of oxygen vacancies to electrodes and across 90 domain walls during annealing, and provide a concrete mechanism for imprinting a 90 domain wall. These results shed new light on various experimental observations.The state of the semiconducting ferroelectric crystal is determined by the polarization density p, the strain , the space-charge density , and the defect density N d , each of which we treat as field quantities. We assume here that all defects are donors motivated...

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Section: Prl 95 247603 (2005) P H Y S I C a L R E V I E W L E T T E supporting

confidence: 69%

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confidence: 99%

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Depletion Layers and Domain Walls in Semiconducting Ferroelectric Thin Films

2005

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“…The effects of the depolarizing field were apparently neglected by the previous authors, Refs. [9][10][11]. Therefore, their general relevance is questionable because, as is shown below, the depolarizing field plays crucial role in determining the dielectric response and the very character of the phase transition.…”

Section: Introductionmentioning

confidence: 99%

“…The depletion effects are especially important in switching devices [6]. The semiconducting behavior of some common ferroelectrics (PZT) was exploited in a series of papers [9][10][11] to account for some specific features of switching, fatigue, and rejuvenation phenomena in ferroelectric thin films.…”

Section: Introductionmentioning

confidence: 99%

Ferroelectric phase transitions in films with depletion charge

Bratkovsky

Levanyuk

2000

Phys. Rev. B

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We consider ferroelectric phase transitions in both short-circuited and biased ferroelectricsemiconductor films with a space (depletion) charge which leads to some unusual behavior. It is shown that in the presence of the charge the polarization separates into 'switchable' and 'nonswitchable' parts. The electric field, appearing due to the space charge, does not wash out the phase transition, which remains second order but takes place at somewhat reduced temperature. At the same time, it leads to a suppression of the ferroelectricity in a near-electrode layer. This conclusion is valid for materials with both second and first order phase transitions in pure bulk samples. Influence of the depletion charge on thermodynamic coercive field reduces mainly to the lowering of the phase transition temperature, and its effect is negligible. The depletion charge can, however, facilitate an appearance of the domain structure which would be detrimental for device performance (fatigue). We discuss some issues of conceptual character, which are generally known but were overlooked in previous works. The present results have general implications for small systems with depletion charge. 77.80.Bh, 77.80.Dj, 85.50.+k

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Thermodynamics of Ferroelectricity

Akdogğan¹,

Safari²

2008

Piezoelectric and Acoustic Materials for Transducer Applications

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Depletion and depolarizing effects in ferroelectric thin films and their manifestations in switching and fatigue

Cited by 51 publications

References 14 publications

Depletion Layers and Domain Walls in Semiconducting Ferroelectric Thin Films

Depletion Layers and Domain Walls in Semiconducting Ferroelectric Thin Films

Ferroelectric phase transitions in films with depletion charge

Thermodynamics of Ferroelectricity

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