Browsing by Author "Jesse, Stephen"

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Deep Data Analysis of Conductive Phenomena on Complex Oxide Interfaces: Physics from Data Mining
(2014-06-01)
Strelcov, Evgheni
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Belianinov, Alexei
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Hsieh, Ying-Hui
;
Jesse, Stephen
;
Baddorf, Arthur P.
Spatial variability of electronic transport in BiFeO3-CoFe2O4 (BFO-CFO) self-assembled heterostructures is explored using spatially resolved first-order reversal curve (FOR) current voltage (IV) mapping. Multivariate statistical analysis of FORC-IV data classifies statistically significant behaviors and maps characteristic responses spatially. In particular, regions of grain, matrix, and grain boundary responses are clearly identified, k-Means and Bayesian demixing analysis suggest the characteristic response be separated into four components, with hysteretic-type behavior localized at the BFO-CFO tubular interfaces. The conditions under which Bayesian components allow direct physical interpretation are explored, and transport mechanisms at the grain boundaries and individual phases are analyzed. This approach conjoins multivariate statistical analysis with physics-based interpretation, actualizing a robust, universal, data-driven approach to problem solving, which can be applied to exploration of local transport and other functional phenomena in other spatially inhomogeneous systems.
Enhanced electric conductivity at ferroelectric vortex cores in BiFeO(3)
(2012-01-01)
Balke, Nina
;
Winchester, Benjamin
;
Ren, Wei
;
Chu, Ying Hao
;
Morozovska, Anna N.
Topological defects in ferroic materials are attracting much attention both as a playground of unique physical phenomena and for potential applications in reconfigurable electronic devices. Here, we explore electronic transport at artificially created ferroelectric vortices in BiFeO(3) thin films. The creation of one-dimensional conductive channels activated at voltages as low as 1V is demonstrated. We study the electronic as well as the static and dynamic polarization structure of several topological defects using a combination of first-principles and phase-field modelling. The modelling predicts that the core structure can undergo a reversible transformation into a metastable twist structure, extending charged domain walls segments through the film thickness. The vortex core is therefore a dynamic conductor controlled by the coupled response of polarization and electron-mobile-vacancy subsystems with external bias. This controlled creation of conductive one-dimensional channels suggests a pathway for the design and implementation of integrated oxide electronic devices based on domain patterning.
Enhanced electric conductivity at ferroelectric vortex cores in BiFeO3
(2012-01-01)
Balke, Nina
;
Winchester, Benjamin
;
Ren, Wei
;
Chu, Ying Hao
;
Morozovska, Anna N.
Topological defects in ferroic materials are attracting much attention both as a playground of unique physical phenomena and for potential applications in reconfigurable electronic devices. Here, we explore electronic transport at artificially created ferroelectric vortices in BiFeO3 thin films. The creation of one-dimensional conductive channels activated at voltages as low as 1V is demonstrated. We study the electronic as well as the static and dynamic polarization structure of several topological defects using a combination of first-principles and phase-field modelling. The modelling predicts that the core structure can undergo a reversible transformation into a metastable twist structure, extending charged domain walls segments through the film thickness. The vortex core is therefore a dynamic conductor controlled by the coupled response of polarization and electron-mobile-vacancy subsystems with external bias. This controlled creation of conductive one-dimensional channels suggests a pathway for the design and implementation of integrated oxide electronic devices based on domain patterning.
High-Frequency Electromechanical Imaging of Ferroelectrics in a Liquid Environment
(2012-06-01)
Balke, Nina
;
Jesse, Stephen
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Chu, Ying-Hao
;
Kalinin, Sergei V.
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材料科學與工程學系
The coupling between electrical and mechanical phenomena is a ubiquitous feature of many information and energy storage materials and devices. In addition to involvement in performance and degradation mechanisms, electromechanical effects underpin a broad spectrum of nanoscale imaging and spectroscopies including piezoresponse force and electrochemical strain microscopies. Traditionally, these studies are conducted under ambient conditions. However, applications related to imaging energy storage and electrophysiological phenomena require operation in a liquid phase and therefore the development of electromechanical probing techniques suitable to liquid environments. Due to the relative high conductivity of most liquids and liquid decomposition at low voltages, the transfer of characterization techniques from ambient to liquid is not straightforward. Here we present a detailed study of ferroelectric domain imaging and manipulation in thin film BiFeO3 using piezoresponse force microscopy in liquid environments as model systems for electromechanical phenomena in general. We explore the use of contact resonance enhancement and the application of multifrequency excitation and detection principles to overcome the experimental problems introduced by a liquid environment. Understanding electromechanical sample characterization in liquid is a key aspect not only for ferroelectric oxides but also for biological and electrochemical sample systems.
Nanoscale Control of Phase Variants in Strain-Engineered BiFeO(3)
(2011-08-01)
Vasudevan, Rama K.
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Liu, Yunya
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Li, Jiangyu
;
Liang, Wen-I
;
Kumar, Amit
Development of magnetoelectric, electromechanical, and photovoltaic devices based on mixed-phase rhombohedral-tetragonal (R-T) BiFeO(3) (BFO) systems is possible only if the control of the engineered R phase variants is realized. Accordingly, we explore the mechanism of a bias induced phase transformation in this system. Single point spectroscopy demonstrates that the T -> R transition is activated at lower voltages compared to T -> - T polarization switching. With phase field modeling, the transition is shown to be electrically driven. We further demonstrate that symmetry of formed R-phase rosettes can be broken by a proximal probe motion, allowing controlled creation of R variants with defined orientation. This approach opens a pathway to designing next-generation magnetoelectronic and data storage devices in the nanoscale.
Nanoscale Control of Phase Variants in Strain-Engineered BiFeO3
(2011-08-01)
Vasudevan, Rama K.
;
Liu, Yunya
;
Li, Jiangyu
;
Liang, Wen-I
;
Kumar, Amit
Development of magnetoelectric, electromechanical, and photovoltaic devices based on mixed-phase rhombohedral-tetragonal (R-T) BiFeO3 (BFO) systems is possible only if the control of the engineered R phase variants is realized. Accordingly, we explore the mechanism of a bias induced phase transformation in this system. Single point spectroscopy demonstrates that the T -> R transition is activated at lower voltages compared to T -> - T polarization switching. With phase field modeling, the transition is shown to be electrically driven. We further demonstrate that symmetry of formed R-phase rosettes can be broken by a proximal probe motion, allowing controlled creation of R variants with defined orientation. This approach opens a pathway to designing next-generation magnetoelectronic and data storage devices in the nanoscale.
Probing Local Electromechanical Effects in Highly Conductive Electrolytes
(2012-11-01)
Balke, Nina
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Tselev, Alexander
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Arruda, Thomas M.
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Jesse, Stephen
;
Chu, Ying-Hao
The functionality of a variety of materials and devices is strongly coupled with electromechanical effects which can be used to characterize their functionality. Of high interest is the investigation of these electromechanical effects on the nanoscale which can be achieved by using scanning probe microscopy. Here, an electrical bias is applied locally to the scanning probe tip, and the mechanical sample response is detected. In some applications with electromechanical phenomena, such as energy storage or for biological samples, a liquid environment is required to provide full functionality and sample stability. However, electromechanical sample characterization has mostly been applied in air or under vacuum due to the difficulties of applying local electric fields in a conductive environment. Here, we present a detailed study of piezoresponse force microscopy of ferroelectric samples in liquid environments as a model system for electromechanical effects in general. The ionic strength of the liquid is varied, and possibilities and limitations of the technique are explored. Numerical simulations are used to explain the observed phenomena and used to suggest strategies to work in liquid environments with high ionic strength.
Probing Local Ionic Dynamics in Functional Oxides at the Nanoscale
(2013-08-01)
Strelcov, Evgheni
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Kim, Yunseok
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Jesse, Stephen
;
Cao, Ye
;
Ivanov, Ilia N.
A scanning probe microscopy technique for probing local ionic dynamics in electrochemically active materials based on the first-order reversal curve current-voltage (FORC-IV) method is presented. FORC-IV imaging mode is applied to a Ca-substituted bismuth ferrite (Ca-BFO) system to separate the electronic and ionic phenomena in this material and visualize the spatial variability of these behaviors. The variable-temperature measurements further demonstrate the interplay between the thermally and electric-field-driven resistance changes in Ca-BFO. The FORC-IV is shown to be a simple, powerful, and flexible method for studying electrochemical activity of materials at the nanoscale and, in conjunction with the electrochemical strain microscopy, it can be used for differentiating ferroelectric and ionic behaviors.
Space- and Time-Resolved Mapping of Ionic Dynamic and Electroresistive Phenomena in Lateral Devices
(2013-08-01)
Strelcov, Evgheni
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Jesse, Stephen
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Huang, Yen-Lin
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Teng, Yung-Chun
;
Kravchenko, Ivan I.
A scanning probe microscopy-based technique for probing local ionic and electronic transport and their dynamic behavior on the 10 ms to 10 s scale is presented. The time-resolved Kelvin probe force microscopy (tr-KPFM) allows mapping of surface potential in both space and time domains, visualizing electronic and ionic charge dynamics and separating underlying processes based on their time responses. Here, tr-KPFM is employed to explore the interplay of the adsorbed surface ions and bulk oxygen vacancies and their role in the resistive switching in a Ca-substituted bismuth ferrite thin film.
Ultrathin limit and dead-layer effects in local polarization switching of BiFeO3
(2012-01-31)
Maksymovych, Peter
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Huijben, Mark
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Pan, Minghu
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Jesse, Stephen
;
Balke, Nina
Using piezoresponse force microscopy in an ultrahigh vacuum, polarization switching has been detected and quantified in epitaxial BiFeO3 films from 200 to about 4 unit cells thick. Local remnant piezoresponse was utilized to probe both ferroelectric properties and effects of imperfect electrical contacts. It was found that the shape of electromechanical hysteresis loops is strongly influenced by an extrinsic dielectric gap, primarily through the suppressing effect of the depolarizing field on the spontaneous polarization in the ultrathin films. Furthermore, statistical analysis of the hysteresis loops has revealed lateral variation of the extrinsic dielectric gap with sub-10-nm resolution. Robust and reproducible ferroelectric properties of nanoscale BiFeO3 indicate its potential for nanoscale applications in information storage and spintronics.
Unraveling Deterministic Mesoscopic Polarization Switching Mechanisms: Spatially Resolved Studies of a Tilt Grain Boundary in Bismuth Ferrite
(2009-07-10)
Rodriguez, Brian J.
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Choudhury, Samrat
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Chu, Y. H.
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Bhattacharyya, Abhishek
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Jesse, Stephen
The deterministic mesoscopic mechanism of ferroelectric domain nucleation is probed at a single atomically-defined model defect: an artificially fabricated bicrystal grain boundary (GB) in an epitaxial bismuth ferrite film. Switching spectroscopy piezoresponse force microscopy (SS-PFM) is used to map the variation of local hysteresis loops at the GB and in its immediate vicinity. It is found that the the influence of the GB on nucleation results in a slight shift of the negative nucleation bias to larger voltages. The mesoscopic mechanisms of domain nucleation in the bulk and at the GB are studied in detail using phase-field modeling, elucidating the complex mechanisms governed by the interplay between ferroelectric and ferroelastic wall energies, depolarization fields, and interface charge. The combination of phase-field modeling and SS-PFM allows quantitative analysis of the mesoscopic mechanisms for polarization switching, and hence suggests a route for unraveling the mechanisms of polarization switching at a single defect level and ultimately optimizing materials properties through microstructure engineering.