Browsing by Author "Melville, A."

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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.
Photovoltaic effects in BiFeO(3)
(2009-08-10)
Yang, S. Y.
;
Martin, L. W.
;
Byrnes, S. J.
;
Conry, T. E.
;
Basu, S. R.
We report a photovoltaic effect in ferroelectric BiFeO(3) thin films. The all-oxide heterostructures with SrRuO(3) bottom and tin doped indium oxide top electrodes are characterized by open-circuit voltages similar to 0.8-0.9 V and external quantum efficiencies up to similar to 10% when illuminated with the appropriate light. Efficiencies are at least an order of magnitude larger than the maximum efficiency under sunlight (AM 1.5) thus far reported for ferroelectric-based devices. The dependence of the measured open-circuit voltage on film thickness suggests contributions to the large open-circuit voltage from both the ferroelectric polarization and band offsets at the BiFeO(3)/tin doped indium oxide interface.
Photovoltaic effects in BiFeO3
(2009-08-10)
Yang, S. Y.
;
Martin, L. W.
;
Byrnes, S. J.
;
Conry, T. E.
;
Basu, S. R.
We report a photovoltaic effect in ferroelectric BiFeO3 thin films. The all-oxide heterostructures with SrRuO3 bottom and tin doped indium oxide top electrodes are characterized by open-circuit voltages similar to 0.8-0.9 V and external quantum efficiencies up to similar to 10% when illuminated with the appropriate light. Efficiencies are at least an order of magnitude larger than the maximum efficiency under sunlight (AM 1.5) thus far reported for ferroelectric-based devices. The dependence of the measured open-circuit voltage on film thickness suggests contributions to the large open-circuit voltage from both the ferroelectric polarization and band offsets at the BiFeO3/tin doped indium oxide interface.