Whither Oxide Electronics?

Ramesh, R.; Schlom, Darrell G.

doi:10.1557/mrs2008.220

Cited by 127 publications

(82 citation statements)

References 63 publications

(52 reference statements)

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“…[1][2][3] Recent work has demonstrated that the functionality of these materials can be further expanded through the formation of superlattices, which can exhibit enhanced properties compared to bulk compounds. While the majority of work in this field has focused on the electronic and ferroic properties of oxide superlattices, 4-9 the impact of heterointerfaces on the local atomic structure has received less attention.…”

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confidence: 99%

Control of octahedral rotations in (LaNiO3)n/(SrMnO

May

Smith²,

Kim³

et al. 2011

Phys. Rev. B

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Oxygen octahedral rotations have been measured in short-period (LaNiO3)n/(SrMnO3)m superlattices using synchrotron diffraction. The in-plane and out-of-plane bond angles and lengths are found to systematically vary with superlattice composition. Rotations are suppressed in structures with m > n, producing a nearly cubic form of LaNiO3. Large rotations are present in structures with m < n, leading to reduced bond angles in SrMnO3. The metal-oxygen-metal bond lengths decrease as rotations are reduced, in contrast to behavior previously observed in strained, single layer films. This result demonstrates that superlattice structures can be used to stabilize non-equilibrium octahedral behavior in a manner distinct from epitaxial strain, providing a novel means to engineer the electronic and ferroic properties of oxide heterostructures.The ABO 3 perovskite oxides exhibit an array of physical properties making them attractive for applications in electronics and energy conversion. 1-3 Recent work has demonstrated that the functionality of these materials can be further expanded through the formation of superlattices, which can exhibit enhanced properties compared to bulk compounds. While the majority of work in this field has focused on the electronic and ferroic properties of oxide superlattices, 4-9 the impact of heterointerfaces on the local atomic structure has received less attention. 10-13 Of particular importance are the rotations and distortions of the BO 6 octahedra, which determine the B-O-B bond angles (θ) and B-O bond lengths (d). As both θ and d couple to the electronic bandwidth, a quantitative understanding of how octahedral rotations are modified in short-period superlattices is necessary in order to control novel electronic phenomena in oxide heterostructures.Motivated by the question of what octahedral behavior is stabilized at the interface between two structurally dissimilar perovskites, we have investigated the bond angles in a systematic series of (LaNiO 3 ) n /(SrMnO 3 ) 2 superlattices. In bulk, LaNiO 3 (LNO) exhibits robust octahedral rotations leading to θ = 165.2 • along all < 001 > directions, 14 with an a − a − a − rotation pattern. 15 In contrast, bulk SrMnO 3 (SMO) is a cubic perovskite (a 0 a 0 a 0 ) lacking octahedral rotations (θ = 180 • ). 16 Due to the short-period of the superlattices investigated and the geometric constraint requiring that the BO 6 octahedra maintain corner connectivity, the octahedral rotations remain coherent throughout the superlattices. We demonstrate that the in-plane and out-of-plane bond angles and lengths can be tuned by altering the superlattice composition [n/(n+m)], allowing for the stabilization of octahedral behavior that differs substantially from that found in bulk compounds.The (LNO) n /(SMO) m superlattices, herein referred to as LnSm, were deposited on SrTiO 3 substrates by ozoneassisted molecular beam epitaxy. 17 The sample thicknesses are between 200 and 215Å. Previous structural (00L) in three samples exhibiting distinct satellite peaks due to t...

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confidence: 99%

Control of octahedral rotations in (LaNiO3)n/(SrMnO

May

Smith²,

Kim³

et al. 2011

Phys. Rev. B

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“…4 Domain formation in ferroelectrics has been largely studied. 2,3,[5][6][7][8][9][10][11][12][13][14][15] In order to adapt to the substrate and to locally minimize the mismatch strain or the depolarizing field, the domains form in a periodic manner. 6,7 It is known that there is a quadratic dependence, W / d 1=2 , of the domain width (W) with the crystal thickness (b).…”

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Thickness scaling of ferroelastic domains in PbTiO3 films on DyScO3

Nesterov

Matzen

Magén

et al. 2013

Applied Physics Letters

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We report on the thickness dependence of the ferroelastic domains of PbTiO 3 films grown on (110)-DyScO 3 with low thicknesses (up to 240 nm), which fall outside the validity range of the square root law proposed by Roytburd. For slow-grown films, the data reveal the linear thickness dependence predicted by Pertsev and Zembilgotov, using a complete elastic description, while a 2/3 scaling exponent is found for fast-grown films. Extremely long domains running all through the samples have been observed in the latter case, compared to the short domains observed in slow-grown films. These differences are ascribed to the in-plane anisotropy for domain wall nucleation, which is likely caused by the anisotropic elastic modulus of the substrate. V C 2013 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4823536]The response of domains and domain walls crucially affects (and often determines) the dielectric properties and switching behavior of ferroelectrics. This is particularly important in thin films where the ferroelectric (180 ) and ferroelastic (non-180 ) domain walls are formed in order to comply with the stringent electrical (large depolarizing field) and mechanical (substrate mismatch strain and clamping) boundary conditions.The size of the domains increases with increasing film thickness as a result of the balance between the depolarizing field energy (for 180 domains) 1 or elastic strain energy (for non-180 domains) 2 and the domain wall formation energy. Thus, the thinner the films, the larger the domain wall density and the greater the influence of the walls on the ferroelectric properties. Moreover, domain walls break spatial symmetry and could add functionalities to the films when present in large amounts. 3 It is therefore most relevant to have good control of the domain formation and the density of domain walls. 4 Domain formation in ferroelectrics has been largely studied. 2,3,[5][6][7][8][9][10][11][12][13][14][15] In order to adapt to the substrate and to locally minimize the mismatch strain or the depolarizing field, the domains form in a periodic manner. 6,7 It is known that there is a quadratic dependence, W / d 1=2 , of the domain width (W) with the crystal thickness (b). In ferroelastic domains (typically 90 domains), this b 1=2 dependence is an approximation in the regime of d ) W. 2 For smaller thicknesses, a linear dependence has been predicted by Pertsev and Zembilgotov (P&Z), 8 but it has not been experimentally confirmed yet.In this paper we investigate the thickness dependence of the periodicity of ferroelastic 90 domains (a/c twins) in the lower thickness regime using PbTiO 3 films grown on DyScO 3 substrates. This combination is chosen because there is a very small lattice mismatch between film and substrate at the growth temperature. This minimizes the formation of defects during growth. As the films are cooled down strain develops and can be relaxed by forming a/c domains. The absence of defects allows these domains to form in a very periodic fashion. 13,16 Interestingly, when the films...

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“…From this perspective, epitaxial thin films are of particular interest due to their characteristics and performances. 1,2 For ferroelectric/ piezoelectric materials, examples of applications that will benefit from this achievement are ferroelectric random access memories, surface acoustic wave devices, and piezoelectric-driven microelectromechanical systems ͑piezo-MEMS͒.…”

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confidence: 99%

Enhanced critical temperature in epitaxial ferroelectric Pb(Zr0.2Ti0.8)O3 thin films on silicon

Sambri¹,

Gariglio²,

Pardo³

et al. 2011

Applied Physics Letters

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The structural and electrical properties of epitaxial Pb͑Zr 0.2 Ti 0.8 ͒O 3 thin films grown on 2 in. ͑001͒ silicon wafers were investigated. Using x-ray diffraction, the lattice behavior of the heterostructure has been studied as a function of temperature, suggesting a 250°C increase of the Pb͑Zr 0.2 Ti 0.8 ͒O 3 ferroelectric-paraelectric transition temperature with respect to the bulk value. This significant enhancement of the critical temperature is understood in terms of a two-dimensional clamping effect.

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Whither Oxide Electronics?

Cited by 127 publications

References 63 publications

Control of octahedral rotations in (LaNiO3)n/(SrMnO

Control of octahedral rotations in (LaNiO3)n/(SrMnO

Thickness scaling of ferroelastic domains in PbTiO3 films on DyScO3

Enhanced critical temperature in epitaxial ferroelectric Pb(Zr0.2Ti0.8)O3 thin films on silicon

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