A5071201153- Ferroelectric and Piezoelectric Materials
- Multiferroics and related materials
- Acoustic Wave Resonator Technologies
- Electronic and Structural Properties of Oxides
- Machine Fault Diagnosis Techniques
- Microwave Dielectric Ceramics Synthesis
- Neural Networks and Applications
- Magnetic and transport properties of perovskites and related materials
- Industrial Technology and Control Systems
- Dielectric properties of ceramics
- Advanced Memory and Neural Computing
- Perovskite Materials and Applications
- Organic Electronics and Photovoltaics
- Bone Tissue Engineering Materials
- Ferroelectric and Negative Capacitance Devices
- Advancements in Solid Oxide Fuel Cells
- Graphene research and applications
- Thin-Film Transistor Technologies
- Machine Learning in Materials Science
- Organic Light-Emitting Diodes Research
- Titanium Alloys Microstructure and Properties
- Transition Metal Oxide Nanomaterials
- Ultrasonics and Acoustic Wave Propagation
- Advanced Thermoelectric Materials and Devices
- Orthopaedic implants and arthroplasty
University of California, Berkeley
2015-2021
Lawrence Berkeley National Laboratory
2016-2019
University of California System
2018
Berkeley College
2018
University of Illinois Urbana-Champaign
2016
Indian Institute of Technology Kanpur
2012
Florida International University
2009-2011
Ferroelectrics, with their spontaneous switchable electric polarization and strong coupling between electrical, mechanical, thermal, optical responses, provide functionalities crucial for a diverse range of applications.Over the past decade, there has been significant progress in epitaxial strain engineering oxide ferroelectric thin films to control enhance nature order, alter susceptibilities, create new modes response which can be harnessed various applications.This review aims cover some...
Abstract Harvesting waste heat for useful purposes is an essential component of improving the efficiency primary energy utilization. Today, approaches such as pyroelectric conversion are receiving renewed interest their ability to turn wasted back into energy. From this perspective, need these approaches, basic mechanisms and processes underlying operation, material device requirements behind reviewed, potential advances in area also discussed.
Leveraging competition between energetically degenerate states to achieve large field-driven responses is a hallmark of functional materials, but routes such are limited. Here, new route effects involving domain-structure demonstrated, which arises from strain-induced spontaneous partitioning PbTiO3 thin films into nearly degenerate, hierarchical domain architectures coexisting c/a and a1 /a2 structures. Using band-excitation piezoresponse force microscopy, this study manipulates...
Abstract A range of modern applications require large and tunable dielectric, piezoelectric or pyroelectric response ferroelectrics. Such effects are intimately connected to the nature polarization how it responds externally applied stimuli. Ferroelectric susceptibilities are, in general, strongly temperature dependent, diminishing rapidly as one transitions away from ferroelectric phase transition ( T C ). In turn, researchers seek new routes manipulate simultaneously enhance broaden...
Abstract Deterministic creation of multiple ferroelectric states with intermediate values polarization remains challenging due to the inherent bi-stability switching. Here we show ability select any desired value via control switching pathway in (111)-oriented PbZr 0.2 Ti 0.8 O 3 films. Such phenomena are driven by kinetic volume fraction two geometrically different domain structures which generated distinct pathways: one direct, bipolar-like and another multi-step process formation a...
The lack of a means for $d\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}t$ characterization the pyroelectric and electrocaloric effects, particularly in ferroic thin films, limits our understanding electrothermal physics essential applying these materials areas such as energy conversion, solid state cooling, sensing. authors develop direct approach to probe polarization-heat interactions thin-film capacitors, including...
Temperature- and electric-field-induced structural transitions in a polydomain ferroelectric can have profound effects on its electrothermal susceptibilities. Here, the role of such ferroelastic domains pyroelectric electrocaloric response is experimentally investigated thin films tetragonal PbZr0.2 Ti0.8 O3 . By utilizing epitaxial strain, rich set states spanning broad thermodynamic phase space are stabilized. Using temperature-dependent scanning-probe microscopy, X-ray diffraction,...
Abstract The ability to manipulate domains underpins function in applications of ferroelectrics. While there have been demonstrations controlled nanoscale manipulation domain structures drive emergent properties, such approaches lack an internal feedback loop required for automatic manipulation. Here, using a deep sequence-to-sequence autoencoder we automate the extraction latent features ferroelectric switching from piezoresponse force spectroscopy tensile-strained PbZr 0.2 Ti 0.8 O 3 with...
Epitaxial strain has been widely used to tune crystal and domain structures in ferroelectric thin films. New avenues of engineering based on varying the composition at nanometer scale have shown generate symmetry breaking large gradients culminating built-in potentials. In this work, we develop routes deterministically control these potentials by exploiting interplay between gradients, accommodation, formation compositionally graded PbZr1–xTixO3 heterostructures. We demonstrate that...
Solid-oxide fuel/electrolyzer cells are limited by a dearth of electrolyte materials with low ohmic loss and an incomplete understanding the structure-property relationships that would enable rational design better materials. Here, using epitaxial thin-film growth, synchrotron radiation, impedance spectroscopy, density-functional theory, impact structural parameters (i.e., unit-cell volume octahedral rotations) on ionic conductivity is delineated in La0.9 Sr0.1 Ga0.95 Mg0.05 O3-δ . As...
Pyroelectrics are a material class that undergoes change in polarization as the temperature of system is varied. This effect can be utilized for applications ranging from thermal imaging and sensing to waste-heat energy conversion thermally driven electron emission. Here, we review recent advances study utilization thin-film pyroelectrics. Leveraging modeling, synthesis, characterization has provided pathway forward one more poorly developed subfields ferroelectricity. We introduce complex...
Graphene's linear dispersion relation and the attendant implications for bipolar electronics applications have motivated a range of experimental efforts aimed at producing p-n junctions in graphene. Here we report electrical transport measurements graphene formed via simple modifications to PbZr$_{0.2}$Ti$_{0.8}$O$_3$ substrate, combined with self-assembled layer ambient environmental dopants. We show that substrate configuration controls local doping region, junction behavior can be...
The emergent ferroelectricity in HfO${}_{2}$-based systems now offers new possibilities beyond high-k dielectricity. In this study, the authors use field-dependent pyroelectric measurements to first prove polar and ferroelectric nature of material then elucidate role defect dipoles on wakeup phenomenon Si-doped HfO${}_{2}$ thin films. This study further reports first-ever direct electrocaloric effect systems. A four-fold larger response, comparison its thermodynamic converse,...
Despite extensive studies on the effects of epitaxial strain evolution lattice and properties materials, considerably less work has explored impact growth dynamics. In this work, we demonstrate a growth-mode transition from 2D-step flow to self-organized, nanoscale 3D-island formation in PbZr0.2Ti0.8O3/SrRuO3/SrTiO3 (001) heterostructures as kinetics process respond strain. With increasing heterostructure thickness misfit dislocation at buried interface, periodic, modulated field is...
Applications such as solid-state waste-heat energy conversion, infrared sensing, and thermally-driven electron emission rely on pyroelectric materials (a subclass of dielectric piezoelectrics) which exhibit temperature-dependent changes in polarization. Although enhanced piezoelectric responses are typically found at polarization instabilities temperature- chemically induced phase boundaries, large effects have been primarily limited study to temperature-induced boundaries. Here, we directly...
Abstract Many energy conversion, sensing, and microelectronic applications based on ferroic materials are determined by the domain structure evolution under applied stimuli. New hyperspectral, multidimensional spectroscopic techniques now probe dynamic responses at relevant length time scales to provide an understanding of how these nanoscale structures impact macroscopic properties. Such approaches, however, remain limited in use because difficulties that exist extracting visualizing...
Abstract The ability to produce atomically precise, artificial oxide heterostructures allows for the possibility of producing exotic phases and enhanced susceptibilities not found in parent materials. Typical ferroelectric materials either exhibit large saturation polarization away from a phase boundary or dielectric susceptibility near boundary. Both permittivity are attained wherein fully epitaxial (PbZr 0.8 Ti 0.2 O 3 ) n /(PbZr 0.4 0.6 2 ( = 2, 4, 6, 8, 16 unit cells) superlattices...
Sometimes worse is better – variations in the chemistry of BaTiO<sub>3</sub>can have unexpected effects on properties.
Domain walls separating regions of ferroelectric material with polarization oriented in different directions are crucial for applications ferroelectrics. Rational design materials requires the development a theory describing how compositional and environmental changes affect domain walls. To model wall systems, discrete microscopic Landau-Ginzburg-Devonshire (dmLGD) approach A- B-site cation displacements serving as order parameters is developed. Application dmLGD to classic BaTiO3 , KNbO3,...