http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Kalinin, Sergei V,Kim, Yunseok,Fong, Dillon D,Morozovska, Anna N IOP 2018 Reports on progress in physics Vol.81 No.3
<P>For over 70 years, ferroelectric materials have been one of the central research topics for condensed matter physics and material science, an interest driven both by fundamental science and applications. However, ferroelectric surfaces, the key component of ferroelectric films and nanostructures, still present a significant theoretical and even conceptual challenge. Indeed, stability of ferroelectric phase <I>per se</I> necessitates screening of polarization charge. At surfaces, this can lead to coupling between ferroelectric and semiconducting properties of material, or with surface (electro) chemistry, going well beyond classical models applicable for ferroelectric interfaces. In this review, we summarize recent studies of surface-screening phenomena in ferroelectrics. We provide a brief overview of the historical understanding of the physics of ferroelectric surfaces, and existing theoretical models that both introduce screening mechanisms and explore the relationship between screening and relevant aspects of ferroelectric functionalities starting from phase stability itself. Given that the majority of ferroelectrics exist in multiple-domain states, we focus on local studies of screening phenomena using scanning probe microscopy techniques. We discuss recent studies of static and dynamic phenomena on ferroelectric surfaces, as well as phenomena observed under lateral transport, light, chemical, and pressure stimuli. We also note that the need for ionic screening renders polarization switching a coupled physical–electrochemical process and discuss the non-trivial phenomena such as chaotic behavior during domain switching that stem from this.</P>
Chang, Hye Jung,Kalinin, Sergei V.,Morozovska, Anna N.,Huijben, Mark,Chu, Ying‐,Hao,Yu, Pu,Ramesh, Ramamoorthy,Eliseev, Evgeny A.,Svechnikov, George S.,Pennycook, Stephen J.,Borisevich, Albina Y WILEY‐VCH Verlag 2011 Advanced Materials Vol.23 No.21
<P><B>Direct atomic displacement mapping at ferroelectric interfaces</B> by aberration corrected scanning transmission electron microscopy(STEM) (a‐STEM image, b‐corresponding displacement profile) is combined with Landau‐Ginsburg‐Devonshire theory to obtain the complete interface electrostatics in real space, including separate estimates for the polarization and intrinsic interface charge contributions. </P>
Nanosculpting of complex oxides by massive ionic transfer
Seol, Daehee,Jesse, Stephen,Park, Sang-Joon,Lee, Woo,Kalinin, Sergei V,Kim, Yunseok IOP 2016 Nanotechnology Vol.27 No.50
<P>Scanning probe microscopy (SPM)-based approaches have been extensively studied as methods to control the structure and properties of materials on the nanoscale. In many cases, the SPM probe is physically utilized to control structure and properties. In addition to physical modulation, it has been reported that voltage can be effectively used to modulate electrochemical phenomena on the sample surface. These studies suggest that electrochemical modulation of the structure and properties is possible by applying a voltage. Herein, in order to demonstrate voltage induced modulation of surface structure, we explored surface nanosculpting by creating electrochemically induced pits on the surface of TiO<SUB>2</SUB> thin films through the application of voltage using the atomic force microscope tip. Using a unipolar negative voltage sweep, pits were successfully generated. Further, the electric potential distribution was simulated to unravel the relationship between the pit volume and the magnitude of the applied voltage. Finally, surface protrusion induced by positive voltage sweep was also observed to elucidate the complete process of electrochemically induced surface modulation. These results can offer fundamental information for understanding how surface structure can be modulated by electrochemical phenomena.</P>
Nanoparticle Shape Evolution and Proximity Effects During Tip-Induced Electrochemical Processes
Yang, Sang Mo,Paranthaman, Mariappan Parans,Noh, Tae Won,Kalinin, Sergei V.,Strelcov, Evgheni American Chemical Society 2016 ACS NANO Vol.10 No.1
<P>Voltage spectroscopies in scanning probe microscopy (SPM) techniques are widely used to investigate the electrochemical processes in nanoscale volumes, which are important for current key applications, such as batteries, fuel cells, catalysts, and memristors. The spectroscopic measurements are commonly performed on a grid of multiple points to yield spatially resolved maps of reversible and irreversible electrochemical functionalities. Hence, the spacing between measurement points is an important parameter to be considered, especially for irreversible electrochemical processes. Here, we report nonlocal electrochemical dynamics in chains of Ag particles fabricated by the SPM tip on a silver ion solid electrolyte. When the grid spacing is small compared with the size of the formed Ag particles,, anomalous chains of unequally sized particles with double periodicity evolve. This behavior is ascribed to a proximity effect during the tip-induced electrochemical process, specifically, size-dependent silver particle growth following the contact between the particles. In addition, fractal shape evolution of the formed Ag structures indicates that the growth-limiting process changes from Ag+/Ag redox reaction to Ag+-ion diffusion with the increase in the applied voltage and pulse duration. This study shows that characteristic shapes of the electrochemical products are good indicators for determining the underlying growth-limiting process, and emergence of complex phenomena during spectroscopic mapping of electrochemical functionalities.</P>
Nonlinear Phenomena in Multiferroic Nanocapacitors: Joule Heating and Electromechanical Effects
Kim, Yunseok,Kumar, Amit,Tselev, Alexander,Kravchenko, Ivan I.,Han, Hee,Vrejoiu, Ionela,Lee, Woo,Hesse, Dietrich,Alexe, Marin,Kalinin, Sergei V.,Jesse, Stephen American Chemical Society 2011 ACS NANO Vol.5 No.11
<P>We demonstrate an approach for probing nonlinear electromechanical responses in BiFeO<SUB>3</SUB> thin film nanocapacitors using half-harmonic band excitation piezoresponse force microscopy (PFM). Nonlinear PFM images of nanocapacitor arrays show clearly visible clusters of capacitors associated with variations of local leakage current through the BiFeO<SUB>3</SUB> film. Strain spectroscopy measurements and finite element modeling point to significance of the Joule heating and show that the thermal effects caused by the Joule heating can provide nontrivial contributions to the nonlinear electromechanical responses in ferroic nanostructures. This approach can be further extended to unambiguous mapping of electrostatic signal contributions to PFM and related techniques.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-11/nn203342v/production/images/medium/nn-2011-03342v_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn203342v'>ACS Electronic Supporting Info</A></P>
Yang, Sang Mo,Strelcov, Evgheni,Paranthaman, M. Parans,Tselev, Alexander,Noh, Tae Won,Kalinin, Sergei V. American Chemical Society 2015 NANO LETTERS Vol.15 No.2
<P>Scanning probe microscopy (SPM) is a powerful tool to investigate electrochemistry in nanoscale volumes. While most SPM-based studies have focused on reactions at the tip–surface junction, charge and mass conservation requires coupled and intrinsically nonlocal cathodic and anodic processes that can be significantly affected by ambient humidity. Here, we explore the role of water in both cathodic and anodic processes, associated charge transport, and topographic volume changes depending on the polarity of tip bias. The first-order reversal curve current–voltage technique combined with simultaneous detection of the sample topography, referred to as FORC-IVz, was applied to a silver solid ion conductor. We found that the protons generated from water affect silver ionic conduction, silver particle formation and dissolution, and mechanical integrity of the material. This work highlights the dual nature (simultaneously local and nonlocal) of electrochemical SPM studies, which should be considered for comprehensive understanding of nanoscale electrochemistry.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2015/nalefd.2015.15.issue-2/nl5040286/production/images/medium/nl-2014-040286_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl5040286'>ACS Electronic Supporting Info</A></P>
Morozovska, Anna N.,Eliseev, Eugene A.,Genenko, Yuri A.,Vorotiahin, Ivan S.,Silibin, Maxim V.,Cao, Ye,Kim, Yunseok,Glinchuk, Maya D.,Kalinin, Sergei V. American Physical Society 2016 Physical Review B Vol.94 No.17
<P>We explore the role of flexoelectric effect in functional properties of nanoscale ferroelectric films with mixed electronic-ionic conductivity. Using a coupled Ginzburg-Landau model, we calculate spontaneous polarization, effective piezoresponse, elastic strain and compliance, carrier concentration, and piezoconductance as a function of thickness and applied pressure. In the absence of flexoelectric coupling, the studied physical quantities manifest well-explored size-induced phase transitions, including transition to paraelectric phase below critical thickness. Similarly, in the absence of external pressure flexoelectric coupling affects properties of these films only weakly. However, the combined effect of flexoelectric coupling and external pressure induces polarizations at the film surfaces, which cause the electric built-in field that destroys the thickness-induced phase transition to paraelectric phase and induces the electretlike state with irreversible spontaneous polarization below critical thickness. Interestingly, the built-in field leads to noticeable increase of the average strain and elastic compliance in this thickness range. We further illustrate that the changes of the electron concentration by several orders of magnitude under positive or negative pressures can lead to the occurrence of high-or low-conductivity states, i.e., the nonvolatile piezoresistive switching, in which the swing can be controlled by the film thickness and flexoelectric coupling. The obtained theoretical results can be of fundamental interest for ferroic systems, and can provide a theoretical model for explanation of a set of recent experimental results on resistive switching and transient polar states in these systems.</P>