Browsing by Author "Chen, L. Q."

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A Strain-Driven Morphotropic Phase Boundary in BiFeO(3)
(2009-11-13)
Zeches, R. J.
;
Rossell, M. D.
;
Zhang, J. X.
;
Hatt, A. J.
;
He, Q.
Piezoelectric materials, which convert mechanical to electrical energy and vice versa, are typically characterized by the intimate coexistence of two phases across a morphotropic phase boundary. Electrically switching one to the other yields large electromechanical coupling coefficients. Driven by global environmental concerns, there is currently a strong push to discover practical lead-free piezoelectrics for device engineering. Using a combination of epitaxial growth techniques in conjunction with theoretical approaches, we show the formation of a morphotropic phase boundary through epitaxial constraint in lead-free piezoelectric bismuth ferrite (BiFeO(3)) films. Electric field-dependent studies show that a tetragonal-like phase can be reversibly converted into a rhombohedral-like phase, accompanied by measurable displacements of the surface, making this new lead-free system of interest for probe-based data storage and actuator applications.
A Strain-Driven Morphotropic Phase Boundary in BiFeO3
(2009-11-13)
Zeches, R. J.
;
Rossell, M. D.
;
Zhang, J. X.
;
Hatt, A. J.
;
He, Q.
Piezoelectric materials, which convert mechanical to electrical energy and vice versa, are typically characterized by the intimate coexistence of two phases across a morphotropic phase boundary. Electrically switching one to the other yields large electromechanical coupling coefficients. Driven by global environmental concerns, there is currently a strong push to discover practical lead-free piezoelectrics for device engineering. Using a combination of epitaxial growth techniques in conjunction with theoretical approaches, we show the formation of a morphotropic phase boundary through epitaxial constraint in lead-free piezoelectric bismuth ferrite (BiFeO3) films. Electric field-dependent studies show that a tetragonal-like phase can be reversibly converted into a rhombohedral-like phase, accompanied by measurable displacements of the surface, making this new lead-free system of interest for probe-based data storage and actuator applications.
Deterministic control of ferroelastic switching in multiferroic materials
(2009-12-01)
Balke, N.
;
Choudhury, S.
;
Jesse, S.
;
Huijben, M.
;
Chu, Y. H.
Multiferroic materials showing coupled electric, magnetic and elastic orderings provide a platform to explore complexity and new paradigms for memory and logic devices. Until now, the deterministic control of non-ferroelectric order parameters in multiferroics has been elusive. Here, we demonstrate deterministic ferroelastic switching in rhombohedral BiFeO(3) by domain nucleation with a scanning probe. We are able to select among final states that have the same electrostatic energy, but differ dramatically in elastic or magnetic order, by applying voltage to the probe while it is in lateral motion. We also demonstrate the controlled creation of a ferrotoroidal order parameter. The ability to control local elastic, magnetic and torroidal order parameters with an electric field will make it possible to probe local strain and magnetic ordering, and engineer various magnetoelectric, domain-wall-based and strain-coupled devices.
Domain Wall Geometry Controls Conduction in Ferroelectrics
(2012-11-01)
Vasudevan, R. K.
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Morozovska, A. N.
;
Eliseev, E. A.
;
Britson, J.
;
Yang, J. -C.
A new paradigm of domain wall. nanoelectronics has emerged recently, in which the domain wall in a ferroic is itself an active device element The ability to spatially. modulate the ferroic order parameter within a single domain wall allows the physical properties to be tailored at will and hence opens vastly unexplored device possibilities: Here, we demonstrate via ambient and ultrahigh-vacuum (UHV) scanning probe microscopy (SPM) measurements in bismuth ferrite that the conductivity of the domain walls can be modulated by up to 500% in the spatial dimension as a function of domain wall curvature. Landau-Ginzburg-Devonshire calculations reveal the conduction is a.. result of carriers or vacancies migrating to neutralize the charge at the farmed interface. Phase field modeling indicates that anisotropic potential distributions can occur even for initially uncharged walls, from polarization dynamics mediated by elastic effects. These results are the first proof of concept for modulation of charge as a function of domain wall geometry by a proximal probe, thereby expanding potential applications for oxide ferroics in future nanoscale electronics.
Exploring Topological Defects in Epitaxial BiFeO(3) Thin Films
(2011-02-01)
Vasudevan, Rama K.
;
Chen, Yi-Chun
;
Tai, Hsiang-Hua
;
Balke, Nina
;
Wu, Pingping
Using a combination of piezoresponse force microscopy (PFM) and phase-field modeling, we demonstrate ubiquitous formation of center-type and possible ferroelectric closure domain arrangements during polarization switching near the ferroelastic domain walls in (100) oriented rhombohedral BiFeO(3). The formation of these topological defects is determined from the vertical and lateral PFM data and confirmed from the reversible changes in surface topography. These observations provide insight into the mechanisms of tip-induced ferroelastic domain control and suggest that formation of topological defect states under the action of local defect- and tip-induced fields is much more common than previously believed.
Exploring Topological Defects in Epitaxial BiFeO3 Thin Films
(2011-02-01)
Vasudevan, Rama K.
;
Chen, Yi-Chun
;
Tai, Hsiang-Hua
;
Balke, Nina
;
Wu, Pingping
Using a combination of piezoresponse force microscopy (PFM) and phase-field modeling, we demonstrate ubiquitous formation of center-type and possible ferroelectric closure domain arrangements during polarization switching near the ferroelastic domain walls in (100) oriented rhombohedral BiFeO3. The formation of these topological defects is determined from the vertical and lateral PFM data and confirmed from the reversible changes in surface topography. These observations provide insight into the mechanisms of tip-induced ferroelastic domain control and suggest that formation of topological defect states under the action of local defect- and tip-induced fields is much more common than previously believed.
Orthorhombic BiFeO3
(2012-12-14)
Yang, J. C.
;
He, Q.
;
Suresha, S. J.
;
Kuo, C. Y.
;
Peng, C. Y.
A new orthorhombic phase of the multiferroic BiFeO3 has been created via strain engineering by growing it on a NdScO3(110)(o) substrate. The tensile-strained orthorhombic BiFeO3 phase is ferroelectric and antiferromagnetic at room temperature. A combination of nonlinear optical second harmonic generation and piezoresponse force microscopy revealed that the ferroelectric polarization in the orthorhombic phase is along the in-plane < 110 >(pc) directions. In addition, the corresponding rotation of the antiferromagnetic axis in this new phase was observed using x-ray linear dichroism. DOI: 10.1103/PhysRevLett.109.247606