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- Atomic force microscopy (1)
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Articles 1 - 30 of 72
Full-Text Articles in Physics
Domain Wall Saddle Point Morphology In Ferroelectric Triglycine Sulfate, C. J. Mccluskey, A. Kumar, Alexei Gruverman, I. Luk’Yanchuk, J. M. Gregg
Domain Wall Saddle Point Morphology In Ferroelectric Triglycine Sulfate, C. J. Mccluskey, A. Kumar, Alexei Gruverman, I. Luk’Yanchuk, J. M. Gregg
Alexei Gruverman Publications
Ferroelectric domain walls, across which there is a divergence in polarization, usually have enhanced electrical conductivity relative to bulk. However, in lead germanate, head-to-head and tail-to-tail walls are electrically insulating. Recent studies have shown that this is because, when oppositely oriented domains meet, polar divergence is obviated by a combination of domain bifurcation and suspected local dipolar rotation. To explore the uniqueness, or otherwise, of this microstructure, we have used tomographic piezoresponse force microscopy to map three-dimensional domain morphologies in another uniaxial ferroelectric system: triglycine sulfate. This mapping reveals an abundance of domain wall saddle points, which are characteristic of …
Ultra-High Carrier Mobilities In Ferroelectric Domain Wall Corbino Cones At Room Temperature, Conor J. Mccluskey, Matthew G. Colbear, James P.V. Mcconville, Shane J. Mccartan, Jesi R. Maguire, Michele Conroy, Kalani Moore, Alan Harvey, Felix Trier, Ursel Bangert, Alexei Gruverman, Manuel Bibes, Amit Kumar, Raymong G.P. Mcquaid, J. Marty Gregg
Ultra-High Carrier Mobilities In Ferroelectric Domain Wall Corbino Cones At Room Temperature, Conor J. Mccluskey, Matthew G. Colbear, James P.V. Mcconville, Shane J. Mccartan, Jesi R. Maguire, Michele Conroy, Kalani Moore, Alan Harvey, Felix Trier, Ursel Bangert, Alexei Gruverman, Manuel Bibes, Amit Kumar, Raymong G.P. Mcquaid, J. Marty Gregg
Alexei Gruverman Publications
Recently, electrically conducting heterointerfaces between dissimilar band-insulators (such as lanthanum aluminate and strontium titanate) have attracted considerable research interest. Charge transport has been thoroughly explored and fundamental aspects of conduction firmly established. Perhaps surprisingly, similar insights into conceptually much simpler conducting homointerfaces, such as the domain walls that separate regions of different orientations of electrical polarisation within the same ferroelectric band-insulator, are not nearly so well-developed. Addressing this disparity, we herein report magnetoresistance in approximately conical 180° charged domain walls, which occur in partially switched ferroelectric thin film single crystal lithium niobate. This system is ideal for such measurements: firstly, …
Ferroelectric Domain Wall Memristor, James P. V. Mcconville, Haidong Lu, Bo Wang, Yueze Tan, Charlotte Cochard, Michele Conroy, Kalani Moore, Alan Harvey, Ursel Bangert, Long-Qing Chen, Alexei Gruverman, J. M. Gregg
Ferroelectric Domain Wall Memristor, James P. V. Mcconville, Haidong Lu, Bo Wang, Yueze Tan, Charlotte Cochard, Michele Conroy, Kalani Moore, Alan Harvey, Ursel Bangert, Long-Qing Chen, Alexei Gruverman, J. M. Gregg
Alexei Gruverman Publications
A domain wall-enabled memristor is created, in thin film lithium niobate capacitors, which shows up to twelve orders of magnitude variation in resistance. Such dramatic changes are caused by the injection of strongly inclined conducting ferroelectric domain walls, which provide conduits for current flow between electrodes. Varying the magnitude of the applied electric-field pulse, used to induce switching, alters the extent to which polarization reversal occurs; this systematically changes the density of the injected conducting domain walls in the ferroelectric layer and hence the resistivity of the capacitor structure as a whole. Hundreds of distinct conductance states can be produced, …
Ch3Nh3Pbi3 Perovskites: Ferroelasticity Revealed, Evgheni Strelcov, Qingfeng Dong, Tao Li, Jungseok Chae, Yuchuan Shao, Yehao Deng, Alexei Gruverman, Jinsong Huang, Andrea Centrone
Ch3Nh3Pbi3 Perovskites: Ferroelasticity Revealed, Evgheni Strelcov, Qingfeng Dong, Tao Li, Jungseok Chae, Yuchuan Shao, Yehao Deng, Alexei Gruverman, Jinsong Huang, Andrea Centrone
Alexei Gruverman Publications
Ferroelectricity has been proposed as a plausible mechanism to explain the high photovoltaic conversion efficiency in organic-inorganic perovskites; however, convincing experimental evidence in support of this hypothesis is still missing. Identifying and distinguishing ferroelectricity from other properties, such as piezoelectricity, ferroelasticity, etc., is typically nontrivial because these phenomena can coexist in many materials. In this work, a combination of microscopic and nanoscale techniques provides solid evidence for the existence of ferroelastic domains in both CH3NH3PbI3 polycrystalline films and single crystals in the pristine state and under applied stress. Experiments show that the configuration of CH …
Anomalous Photovoltaic Effect In Organic-Inorganic Hybrid Perovskite Solar Cells, Yongbo Yuan, Tao Li, Qi Wang, Jie Xing, Alexei Gruverman, Jinsong Huang
Anomalous Photovoltaic Effect In Organic-Inorganic Hybrid Perovskite Solar Cells, Yongbo Yuan, Tao Li, Qi Wang, Jie Xing, Alexei Gruverman, Jinsong Huang
Alexei Gruverman Publications
Organic-inorganic hybrid perovskites (OIHPs) have been demonstrated to be highly successful photovoltaic materials yielding very-high-efficiency solar cells. We report the room temperature observation of an anomalous photovoltaic (APV) effect in lateral structure OIHP devices manifested by the device’s open-circuit voltage (VOC) that is much larger than the bandgap of OIHPs. The persistent VOC is proportional to the electrode spacing, resembling that of ferroelectric photovoltaic devices. However, the APV effect in OIHP devices is not caused by ferroelectricity. The APV effect can be explained by the formation of tunneling junctions randomly dispersed in the polycrystalline films, which allows …
Theoretical Approach To Electroresistance In Ferroelectric Tunnel Junctions, Sou-Chi Chang, Azad Naeemi, Dmitri E. Nikonov, Alexei Gruverman
Theoretical Approach To Electroresistance In Ferroelectric Tunnel Junctions, Sou-Chi Chang, Azad Naeemi, Dmitri E. Nikonov, Alexei Gruverman
Alexei Gruverman Publications
In this paper, a theoretical approach comprising the nonequilibrium Green’s function method for electronic transport and the Landau-Khalatnikov equation for electric polarization dynamics is presented to describe polarization-dependent tunneling electroresistance (TER) in ferroelectric tunnel junctions. Using appropriate contact, interface, and ferroelectric parameters, the measured current-voltage characteristic curves in both inorganic (Co/BaTiO3/La0.67Sr0.33MnO3) and organic (Au/PVDF/W) ferroelectric tunnel junctions can be well described by the proposed approach. Furthermore, under this theoretical framework, the controversy of opposite TER signs observed experimentally by different groups in Co/BaTiO3/La0.67Sr0.33MnO3 systems is …
Domain Wall Conductivity In Semiconducting Hexagonal Ferroelectric Tbmno3 Thin Films, D. J. Kim, J. G. Connell, S. S. A. Seo, Alexei Gruverman
Domain Wall Conductivity In Semiconducting Hexagonal Ferroelectric Tbmno3 Thin Films, D. J. Kim, J. G. Connell, S. S. A. Seo, Alexei Gruverman
Alexei Gruverman Publications
Although enhanced conductivity of ferroelectric domain boundaries has been found in BiFeO3 and Pb(Zr,Ti)O3 films as well as hexagonal rare-earth manganite single crystals, the mechanism of the domain wall conductivity is still under debate. Using conductive atomic force microscopy, we observe enhanced conductance at the electrically-neutral domain walls in semiconducting hexagonal ferroelectric TbMnO3 thin films where the structure and polarization direction are strongly constrained along the c-axis. This result indicates that domain wall conductivity in ferroelectric rare-earth manganites is not limited to charged domain walls. We show that the observed conductivity in the TbMnO3 films is …
Scaling Of Electroresistance Effect In Fully Integrated Ferroelectric Tunnel Junctions, Mohammad Abuwasib, Haidong Lu, Tao Li, Pratyush Buragohain, Hyungwoo Lee, Chang-Beom Eom, Alexei Gruverman, Uttam Singisetti
Scaling Of Electroresistance Effect In Fully Integrated Ferroelectric Tunnel Junctions, Mohammad Abuwasib, Haidong Lu, Tao Li, Pratyush Buragohain, Hyungwoo Lee, Chang-Beom Eom, Alexei Gruverman, Uttam Singisetti
Alexei Gruverman Publications
Systematic investigation of the scalability for tunneling electroresistance (TER) of integrated Co/BaTiO3/SrRuO3 ferroelectric tunnel junctions (FTJs) has been performed from micron to deep submicron dimensions. Pulsed measurements of the transient currents confirm the ferroelectric switching behavior of the FTJs, while the hysteresis loops measured by means of piezoresponse force microscopy verify the scalability of these structures. Fully integrated functional FTJ devices with the size of 300×300 nm2 exhibiting a tunneling electroresistance (TER) effect of the order of 2.7×104% have been fabricated and tested. Measured current density of 75 A/cm2 for the ON state …
Contact Resistance To Srruo3 And La0.67Sr0.33Mno3 Epitaxial Films, Mohammad Abuwasib, Hyungwoo Lee, Alexei Gruverman, Chang-Beom Eom, Uttam Singisetti
Contact Resistance To Srruo3 And La0.67Sr0.33Mno3 Epitaxial Films, Mohammad Abuwasib, Hyungwoo Lee, Alexei Gruverman, Chang-Beom Eom, Uttam Singisetti
Alexei Gruverman Publications
Contact resistance to the metallic oxide electrodes, SrRuO3 (SRO) and La0.67Sr0.33MnO3 (LSMO), is an important parameter that affects the ferroelectric tunnel junction (FTJ) device performance. We have systematically studied the contact resistance between metallic oxide electrodes (SRO, LSMO) and contact metal overlayers (Ti, Pt) after exposure to various processing environments. Specific contact resistivity (ρc) for Ti and Pt contact metals and the sheet resistance (Rsh) of the metallic oxides are measured after exposure to different reactive ion plasma process steps. Sheet resistance degradation was observed for both SRO and …
Electrostatic Charge On Flying Hummingbirds And Its Potential Role In Pollination, Marc Badger, Victor Manuel Ortega-Jimenez, Lisa Von Ribenau, Ashley Smiley, Robert Dudley, Alexei Gruverman , Editor
Electrostatic Charge On Flying Hummingbirds And Its Potential Role In Pollination, Marc Badger, Victor Manuel Ortega-Jimenez, Lisa Von Ribenau, Ashley Smiley, Robert Dudley, Alexei Gruverman , Editor
Alexei Gruverman Publications
Electrostatic phenomena are known to enhance both wind- and insect-mediated pollination, but have not yet been described for nectar-feeding vertebrates. Here we demonstrate that wild Anna's Hummingbirds (Calypte anna) can carry positive charges up to 800 pC while in flight (mean ± s.d.: 66 ± 129 pC). Triboelectric charging obtained by rubbing an isolated hummingbird wing against various plant structures generated charges up to 700 pC. A metal hummingbird model charged to 400 pC induced bending of floral stamens in four plants (Nicotiana, Hemerocallis, Penstemon, and Aloe spp.), and also attracted falling Lycopodium spores at distances of < 2 mm. Electrostatic forces may therefore influence pollen transfer onto nectar-feeding birds.
Multiferroic Tunnel Junctions And Ferroelectric Control Of Magnetic State At Interface, Y. W. Yin, M. Raju, W. J. Hu, John D. Burton, Y.-M. Kim, A. Y. Borisevich, S. J. Pennycook, S. M. Yang, T. W. Noh, Alexei Gruverman, X. G. Li, Z. D. Zhang, Evgeny Y. Tsymbal, Qi Li
Multiferroic Tunnel Junctions And Ferroelectric Control Of Magnetic State At Interface, Y. W. Yin, M. Raju, W. J. Hu, John D. Burton, Y.-M. Kim, A. Y. Borisevich, S. J. Pennycook, S. M. Yang, T. W. Noh, Alexei Gruverman, X. G. Li, Z. D. Zhang, Evgeny Y. Tsymbal, Qi Li
Alexei Gruverman Publications
As semiconductor devices reach ever smaller dimensions, the challenge of power dissipation and quantum effect place a serious limit on the future device scaling. Recently, a multiferroic tunnel junction (MFTJ) with a ferroelectric barrier sandwiched between two ferromagnetic electrodes has drawn enormous interest due to its potential applications not only in multi-level data storage but also in electric field controlled spintronics and nanoferronics. Here, we present our investigations on four-level resistance states, giant tunneling electroresistance (TER) due to interfacial magnetoelectric coupling, and ferroelectric control of spin polarized tunneling in MFTJs. Coexistence of large tunneling magnetoresistance and TER has been observed …
Ferroelectric Switching In Epitaxial Gete Films, A. V. Kolobov, D. J. Kim, A. Giussani, P. Fons, J. Tominaga, R. Calarco, Alexei Gruverman
Ferroelectric Switching In Epitaxial Gete Films, A. V. Kolobov, D. J. Kim, A. Giussani, P. Fons, J. Tominaga, R. Calarco, Alexei Gruverman
Alexei Gruverman Publications
In this paper, using a resonance-enhanced piezoresponse force microscopy approach supported by density functional theory computer simulations, we have demonstrated the ferroelectric switching in epitaxial GeTe films. It has been shown that in films with thickness on the order of several nanometers reversible reorientation of polarization occurs due to swapping of the shorter and longer Ge-Te bonds in the interior of the material. It is also hinted that for ultra thin films consisting of just several atomic layers weakly bonded to the substrate, ferroelectric switching may proceed through exchange of Ge and Te planes within individual GeTe layers.
Mechanical Writing Of Ferroelectric Polarization, Haidong Lu, C.-W. Bark, D. Esque De Los Ojos, J. Alcala, Chang-Beom Eom, G. Catalan, Alexei Gruverman
Mechanical Writing Of Ferroelectric Polarization, Haidong Lu, C.-W. Bark, D. Esque De Los Ojos, J. Alcala, Chang-Beom Eom, G. Catalan, Alexei Gruverman
Alexei Gruverman Publications
Ferroelectric materials are characterized by a permanent electric dipole that can be reversed through the application of an external voltage, but a strong intrinsic coupling between polarization and deformation also causes all ferroelectrics to be piezoelectric, leading to applications in sensors and high-displacement actuators. A less explored property is flexoelectricity, the coupling between polarization and a strain gradient. We demonstrate that the stress gradient generated by the tip of an atomic force microscope can mechanically switch the polarization in the nanoscale volume of a ferroelectric film. Pure mechanical force can therefore be used as a dynamic tool for polarization control …
Complex Domain Structure In Relaxed Pbtio3 Thick Films Grown On (100)Csrruo3//(100)Srtio3 Substrates, Shintaro Yasui, Yoshitaka Ehara, Satoru Utsugi, Mitsumasa Nakajima, Hiroshi Funakubo, Alexei Gruverman
Complex Domain Structure In Relaxed Pbtio3 Thick Films Grown On (100)Csrruo3//(100)Srtio3 Substrates, Shintaro Yasui, Yoshitaka Ehara, Satoru Utsugi, Mitsumasa Nakajima, Hiroshi Funakubo, Alexei Gruverman
Alexei Gruverman Publications
Domain structures of epitaxial PbTiO3 films grown on (100)cSrRuO3//(100)SrTiO3 substrates by metalorganic chemical vapor deposition were investigated by x-ray diffraction (XRD) and piezoresponse force microscopy (PFM) techniques. It was found that with increasing film thickness, the domain structure changed from simple (001) polarization orientation to a complicated mixture of (001) and (100) orientations. PFM mappings showed that in the thicker films (~1100 nm), the zigzag (001)/(100) domain boundaries made an angle of approximately 87° instead of 90° typically observed in (001)/(100) domain patterns in thinner (<300 nm) films. Full-relaxed tilting angle θ1+ θ2+θ3 …
Tunnel Electroresistance In Junctions With Ultrathin Ferroelectric Pb(Zr0.2ti0.8)O3 Barriers, Daniel Pantel, Haidong Lu, Silvana Goetze, Peter Werner, Dong Jik Kim, Alexei Gruverman, Dietrich Hesse, Marin Alexe
Tunnel Electroresistance In Junctions With Ultrathin Ferroelectric Pb(Zr0.2ti0.8)O3 Barriers, Daniel Pantel, Haidong Lu, Silvana Goetze, Peter Werner, Dong Jik Kim, Alexei Gruverman, Dietrich Hesse, Marin Alexe
Alexei Gruverman Publications
In ferroelectric tunnel junctions, the ferroelectric polarization state of the barrier influences the quantum-mechanical tunneling through the junction, resulting in tunnel electroresistance (TER). Here, we investigate tunnel electroresistance in Co/PbZr0.2Ti0.8O3/La0.7Sr0.3MnO3 tunnel junctions. The ferroelectric polarization in tunnel junctions with 1.2-1.6 nm (three to four unit cells) PbZr0.2Ti0.8O3 thickness and an area of 0.04 μm2 can be switched by about 1 V yielding a resistive ON/OFF-ratio of about 300 at 0.4 V. Combined piezoresponse force microscopy and electronic transport investigations of these junctions reveal …
Electric Modulation Of Magnetization At The Batio3/La0.67sr0.33mno3 Interfaces, H. Lu, Thomas A. George, Yong Wang, Ihor Ketsman, John D. Burton, C.-W. Bark, Sangjin Ryu, Dong Jik Kim, J. Wang, Christian Binek, Peter A. Dowben, Andrei Sokolov, C. B. Eom, Evgeny Y. Tsymbal, Alexei Gruverman
Electric Modulation Of Magnetization At The Batio3/La0.67sr0.33mno3 Interfaces, H. Lu, Thomas A. George, Yong Wang, Ihor Ketsman, John D. Burton, C.-W. Bark, Sangjin Ryu, Dong Jik Kim, J. Wang, Christian Binek, Peter A. Dowben, Andrei Sokolov, C. B. Eom, Evgeny Y. Tsymbal, Alexei Gruverman
Alexei Gruverman Publications
We report large (>10%) magnetization modulation by ferroelectric polarization reversal in the ferroelectric-ferromagnetic BaTiO3/La0.67Sr0.33MnO3 (BTO/LSMO) heterostructures. We find that the electrically induced change in magnetization is limited to the BTO/LSMO interface but extends about 3 nm deep into the LSMO layer—far beyond the expected screening length of metallic LSMO. It is suggested that this effect is due to a metal-insulator transition occurring at the BTO/LSMO interface as a result of electrostatic doping.
Mesoscale Flux-Closure Domain Formation In Single-Crystal Batio3, R. G.P. Mcquaid, L. J. Mcgilly, Pankaj Sharma, Alexei Gruverman, J. M. Gregg
Mesoscale Flux-Closure Domain Formation In Single-Crystal Batio3, R. G.P. Mcquaid, L. J. Mcgilly, Pankaj Sharma, Alexei Gruverman, J. M. Gregg
Alexei Gruverman Publications
Over 60 years ago, Charles Kittel predicted that quadrant domains should spontaneously form in small ferromagnetic platelets. He expected that the direction of magnetization within each quadrant should lie parallel to the platelet surface, minimizing demagnetizing fields, and that magnetic moments should be configured into an overall closed loop, or flux-closure arrangement. Although now a ubiquitous observation in ferromagnets, obvious flux-closure patterns have been somewhat elusive in ferroelectric materials. This is despite the analogous behaviour between these two ferroic subgroups and the recent prediction of dipole closure states by atomistic simulations research. Here we show Piezoresponse Force Microscopy images of …
Anisotropy Of Domain Growth In Epitaxial Ferroelectric Capacitors, D. Wu, I. Vrejoiu, M. Alexe, Alexei Gruverman
Anisotropy Of Domain Growth In Epitaxial Ferroelectric Capacitors, D. Wu, I. Vrejoiu, M. Alexe, Alexei Gruverman
Alexei Gruverman Publications
Piezoresponse force microscopy (PFM) has been applied to investigate the switching kinetics in microscale epitaxial Pb(Zr,Ti)O3 capacitors. It is shown that transition from low to high field range brings about a qualitative change in domain growth kinetics, namely, laterally isotropic growth in the high fields as opposed to highly anisotropic growth in the low fields. It is suggested that anisotropy of domain growth can be attributed to orientational variations in the activation energy due to film microstructure. Fitting the switching kinetics using the Kolmogorov–Avrami–Ishibashi model shows excellent agreement with the PFM experimental data and yields the integer values of …
Spatial Variations In Local Switching Parameters Of Ferroelectric Random Access Memory Capacitors, D. Wu, I. Kunishima, S. Roberts, Alexei Gruverman
Spatial Variations In Local Switching Parameters Of Ferroelectric Random Access Memory Capacitors, D. Wu, I. Kunishima, S. Roberts, Alexei Gruverman
Alexei Gruverman Publications
Spatially resolved studies of the switching behavior of micrometer scale Pb(Zr,Ti)O3 capacitors have been performed by piezoresponse force microscopy (PFM). PFM spectroscopy and bias-dependent imaging of domain patterns have been used to investigate variability in local switching parameters and address the capacitor scaling effect on switching. It was found that average coercive voltage and imprint bias are independent of capacitor size and are similar to the corresponding parameters obtained by polarization hysteresis measurements. This can be attributed to the slow switching kinetics during quasistatic PFM measurements. The obtained results demonstrate a possibility of testing the submicron capacitors in real …
Nanoscale Insight Into The Statics And Dynamics Of Polarization Behavior In Thin Film Ferroelectric Capacitors, Alexei Gruverman
Nanoscale Insight Into The Statics And Dynamics Of Polarization Behavior In Thin Film Ferroelectric Capacitors, Alexei Gruverman
Alexei Gruverman Publications
In this study, we review recent advances in PFM studies of micrometer scale ferroelectric capacitors, summarize the experimental PFM-based approach to investigation of fast switching processes, illustrate what information can be obtained from PFM experiments on domains kinetics, and delineate the scaling effect on polarization reversal mechanism. Particular attention is given to PFM studies of mechanical stress effect on polarization stability.
Imaging Mechanism Of Piezoresponse Force Microscopy In Capacitor Structures, Sergei V. Kalinin, Brian J. Rodriguez, Seung-Hyun Kim, Suk-Kyoung Hong, Alexei Gruverman, Eugene E. Eliseev
Imaging Mechanism Of Piezoresponse Force Microscopy In Capacitor Structures, Sergei V. Kalinin, Brian J. Rodriguez, Seung-Hyun Kim, Suk-Kyoung Hong, Alexei Gruverman, Eugene E. Eliseev
Alexei Gruverman Publications
The image formation mechanism in piezoresponse force microscopy (PFM) of capacitor structures is analyzed. We demonstrate that the spatial resolution is a bilinear function of film and top electrode thicknesses and derive the corresponding analytical expressions. For many perovskites, the opposite contributions of d31 and d33 components can result in anomalous domain wall profiles. This analysis establishes the applicability limits of PFM for polarization dynamics studies in capacitors and applies them to other structural probes, including focused x-ray studies of capacitor structures.
Piezoresponse Force Microscopy Studies Of Switching Behavior Of Ferroelectric Capacitors On A 100-Ns Time Scale, Alexei Gruverman, D. Wu, J. F. Scott
Piezoresponse Force Microscopy Studies Of Switching Behavior Of Ferroelectric Capacitors On A 100-Ns Time Scale, Alexei Gruverman, D. Wu, J. F. Scott
Alexei Gruverman Publications
Piezoresponse force microscopy is a powerful technique for nm-scale studies but is usually limited by response time. In this Letter, we report the first direct studies of ferroelectric capacitor switching on a submicrosecond time scale. Simultaneous domain imaging and sub-µs transient current measurements establish a direct relationship between polarization P(t) and domain kinetics. Switching times scale with capacitor size over an order of magnitude. Small capacitors, where polarization reversal is dominated by domain wall motion, switch faster at high fields but more slowly at low fields while larger capacitors do the reverse.
Experimental Evidence Of Strain Relaxed Domain Structure In (100)/(001)-Oriented Epitaxial Lead Titanate Thick Films Grown By Metal Organic Chemical Vapor Deposition, Hiroshi Nakaki, Yong Kwan Kim, Shintaro Yokoyama, Rikyu Ikariyama, Hiroshi Funakubo, S. K. Streiffer, Ken Nishida, Keisuke Saito, Alexei Gruverman
Experimental Evidence Of Strain Relaxed Domain Structure In (100)/(001)-Oriented Epitaxial Lead Titanate Thick Films Grown By Metal Organic Chemical Vapor Deposition, Hiroshi Nakaki, Yong Kwan Kim, Shintaro Yokoyama, Rikyu Ikariyama, Hiroshi Funakubo, S. K. Streiffer, Ken Nishida, Keisuke Saito, Alexei Gruverman
Alexei Gruverman Publications
Epitaxial (100)/(001)-oriented PbTiO3 films with thickness of 2.8 μm were grown on Nb-doped (100) SrTiO3 substrates by pulsed metal organic chemical vapor deposition. Complex domain structures consisting of c-domains (c1) and three types of a-domains (a1, a2, and a3) were observed by piezoresponse force microscopy in conjunction with high-resolution x-ray diffraction analysis. The obtained results suggest that (a2/a3) and (a1/c1) domain configurations represent mostly strain-relaxed structures. This conclusion is in good agreement with theoretical predictions made for thick films [Phys. State., Solidi 37, 329 (1976)].
Peculiar Effect Of Mechanical Stress On Polarization Stability In Micrometer-Scale Ferroelectric Capacitors, Alexei Gruverman, J. S. Cross, W.S. Oates
Peculiar Effect Of Mechanical Stress On Polarization Stability In Micrometer-Scale Ferroelectric Capacitors, Alexei Gruverman, J. S. Cross, W.S. Oates
Alexei Gruverman Publications
Piezoresponse force microscopy (PFM) has been used to study the polarization stability in micrometer size Pb(Zr,Ti)O3 capacitors. It is shown that the top electrode thickness has a profound effect on the equilibrium polarization state of poled capacitors triggering spontaneous polarization backswitching in the absence of an applied electric field and leading to the formation of an abnormal domain pattern. PFM examination of poled capacitors with thick (250 nm) top electrodes reveals domain patterns with the central regions always oriented in the direction opposite to the applied field. It is suggested that the driving force behind the observed effect is …
Nanodomain Faceting In Ferroelectrics, J. F. Scott, Alexei Gruverman, D. Wu, M. Alexe
Nanodomain Faceting In Ferroelectrics, J. F. Scott, Alexei Gruverman, D. Wu, M. Alexe
Alexei Gruverman Publications
We show that after long times (24 h), individual circular domains in 50 nm thick [0 0 1] epitaxial films of ferroelectric lead zirconate titanate (PZT) develop facets due to the crystalline anisotropy, e.g. along [1 0 0] directions. This appears to be a creep process (Tybell et al. 2002 Phys. Rev. Lett. 89 097601; Paruch et al. 2006 J. Appl. Phys. 100 051608) and was first seen in a nanoarray of 180° domains (Ganpule et al. 2002 Phys. Rev. B 65 014101). The effect is independent of polarity and thus rules out any electronic dependence on different work functions …
Vortex Ferroelectric Domains, Alexei Gruverman, D. Wu, H.-J. Fan, I. Vrejoiu, M. Alexe, R. J. Harrison, J. F. Scott
Vortex Ferroelectric Domains, Alexei Gruverman, D. Wu, H.-J. Fan, I. Vrejoiu, M. Alexe, R. J. Harrison, J. F. Scott
Alexei Gruverman Publications
We show experimental switching data on microscale capacitors of lead–zirconate–titanate (PZT), which reveal time-resolved domain behavior during switching on a 100 ns scale. For small circular capacitors, an unswitched domain remains in the center while complete switching is observed in square capacitors. The observed effect is attributed to the formation of a vortex domain during polarization switching in small circular capacitors. This dynamical behavior is modeled using the Landau–Lifshitz–Gilbert equations and found to be in agreement with experiment. This simulation implies rotational motion of polarization in the xy plane, a Heisenberg-like result supported by the recent model of Naumov and …
Abnormal Domain Switching In Pb(Zr, Ti)O3 Thin Film Capacitors, Aiying Wu, Paula Vilarinho, Dong Wu, Alexei Gruverman
Abnormal Domain Switching In Pb(Zr, Ti)O3 Thin Film Capacitors, Aiying Wu, Paula Vilarinho, Dong Wu, Alexei Gruverman
Alexei Gruverman Publications
Observation of abnormal (against the applied electric field) domain switching in Pb(ZrxTi1−x)O3 films by piezoresponse force microscopy is reported. In some grains polarization orients opposite to the external field in the presence of the applied field, while the rest of the film volume switches in a normal way. This effect is observed in thin film capacitors which excludes charge injection effect and spontaneous backswitching due the built-in field, which is the possible reason for this behavior. The abnormal switching behavior is attributed to the charge compensation effect at the boundaries of the grains with rhombohedral …
Peritubular Dentin Lacks Piezoelectricity, S. Habelitz, B. J. Rodriguez, S. J. Marshall, G. W. Marshall, Sergei V. Kalinin, Alexei Gruverman
Peritubular Dentin Lacks Piezoelectricity, S. Habelitz, B. J. Rodriguez, S. J. Marshall, G. W. Marshall, Sergei V. Kalinin, Alexei Gruverman
Alexei Gruverman Publications
Dentin is a mesenchymal tissue, and, as such, is based on a collagenous matrix that is reinforced by apatite mineral. Collagen fibrils show piezoelectricity, a phenomenon that is used by piezoresponse force microscopy (PFM) to obtain high-resolution images. We applied PFM to image human dentin with 10-nm resolution, and to test the hypothesis that zones of piezoactivity, indicating the presence of collagen fibrils, can be distinguished in dentin. Piezoelectricity was observed by PFM in the dentin intertubular matrix, while the peritubular dentin remained without response. High-resolution imaging of chemically treated intertubular dentin attributed the piezoelectric effect to individual collagen fibrils …
Probing Intrinsic Polarization Properties In Bismuth-Layered Ferroelectric Films, Takayuki Watanabe, Hiroshi Funakubo, Minoru Osada, Hiroshi Uchida, B. J. Rodriguez, Alexei Gruverman
Probing Intrinsic Polarization Properties In Bismuth-Layered Ferroelectric Films, Takayuki Watanabe, Hiroshi Funakubo, Minoru Osada, Hiroshi Uchida, B. J. Rodriguez, Alexei Gruverman
Alexei Gruverman Publications
The authors report on an approach to establish intrinsic polarization properties in bismuth-layered ferroelectric films by piezoelectric coefficient and soft-mode spectroscopy, as well as by a direct polarization–electric field hysteresis. In epitaxially grown (Bi4−xNdx)Ti3O12 (0≤x≤0.73) films, they show that these complementary characterizations can phenomenologically and thermodynamically represent the intrinsic polarization states in (Bi4−xNdxTi3O12 films, and the intrinsic Ps of 67 μC/cm2 is estimated for pure Bi4Ti3O12, superior to 50 μC/cm2 in bulk single crystal. Their …
Electromechanical Behavior In Biological Systems At The Nanoscale, Alexei Gruverman, Brain J. Rodriguez, Sergei Kalinin
Electromechanical Behavior In Biological Systems At The Nanoscale, Alexei Gruverman, Brain J. Rodriguez, Sergei Kalinin
Alexei Gruverman Publications
Hierarchical structure of connective and calcified tissues from the macro- to nanoscale level determines the mechanical and biological functionality of biological materials and has been the focus of numerous recent studies. Further progress in this field requires development of microscopic techniques capable of probing materials properties, including local composition, crystallographic orientation, and mechanical properties on the nanometer-length scale. Here, we describe a piezoresponse force microscopy (PFM) approach to high-resolution imaging of biological systems, based on detection of the local piezoelectric response. Samples include human tooth, femoral cartilage, deer antler, and butterfly wing scales. PFM allows differentiation between organic and mineral …