Options
et al.
Preferred name
et al.
Official Name
et al.
Research Output
Now showing 1 - 10 of 11
- PublicationTip-induced domain structures and polarization switching in ferroelectric amino acid glycine(American Institute of Physics, 2015)
; ; ; ; Bioorganic ferroelectrics and piezoelectrics are becoming increasingly important in view of their intrinsic compatibility with biological environment and biofunctionality combined with strong piezoelectric effect and a switchable polarization at room temperature. Here, we study tip-induced domain structures and polarization switching in the smallest amino acid b-glycine, representing a broad class of non-centrosymmetric amino acids. We show that b-glycine is indeed a roomtemperature ferroelectric and polarization can be switched by applying a bias to non-polar cuts via a conducting tip of atomic force microscope (AFM). Dynamics of these in-plane domains is studied as a function of an applied voltage and pulse duration. The domain shape is dictated by polarization screening at the domain boundaries and mediated by growth defects. Thermodynamic theory is applied to explain the domain propagation induced by the AFM tip. Our findings suggest that the properties of b-glycine are controlled by the charged domain walls which in turn can be manipulated by an external bias.399Scopus© Citations 23 - PublicationReal space mapping of polarization dynamics and hysteresis loop formation in relaxor-ferroelectric PbMg1/3Nb2/3O3-PbTiO3 solid solutionsPolarization switching in ergodic relaxor and ferroelectric phases in the PbMg1/3Nb2/3O3-PbTiO3 (PMN-PT) system is studied using piezoresponse force microscopy, single point electromechanical relaxation measurements, and voltage spectroscopy mapping. The dependence of relaxation behavior on voltage pulse amplitude and time is found to follow a universal logarithmic behavior with a nearly constant slope. This behavior is indicative of the progressive population of slow relaxation states, as opposed to a linear relaxation in the presence of a broad relaxation time distribution. The role of relaxation behavior, ferroelectric nonlinearity, and the spatial inhomogeneity of the tip field on hysteresis loop behavior is analyzed in detail. The hysteresis loops for ergodic PMN-10\%PT are shown to be kinetically limited, while in PMN with larger PT content, true ferroelectric hysteresis loops with low nucleation biases are observed. (C) 2010 American Institute of Physics. [doi:10.1063/1.3474961]
570Scopus© Citations 45 - PublicationLocal piezoresponse and polarization switching in nucleobase thymine microcrystals(American Institute of Physics, 2015)
; ; ; ; Thymine (2-oxy-4-oxy-5 methyl pyrimidine) is one of the four nucleobases of deoxyribonucleic acid (DNA). In the DNA molecule, thymine binds to adenine via two hydrogen bonds, thus stabilizing the nucleic acid structure and is involved in pairing and replication. Here, we show that synthetic thymine microcrystals grown from the solution exhibit local piezoelectricity and apparent ferroelectricity, as evidenced by nanoscale electromechanical measurements via Piezoresponse Force Microscopy. Our experimental results demonstrate significant electromechanical activity and polarization switchability of thymine, thus opening a pathway for piezoelectric and ferroelectric-based applications of thymine and, perhaps, of other DNA nucleobase materials. The results are supported by molecular modeling of polarization switching under an external electric field.630Scopus© Citations 12 - PublicationQuantitative determination of tip parameters in piezoresponse force microscopy(American Institute of Physics, 2007-05-24)
; ; ; One of the key limiting factors in the quantitative interpretation of piezoresponse force microscopy (PFM) is the lack of knowledge on the effective tip geometry. Here the authors derive analytical expressions for a 180 degrees domain wall profile in PFM for the point charge, sphere plane, and disk electrode models of the tip. An approach for the determination of the effective tip parameters from the wall profile is suggested and illustrated for several ferroelectric materials. The calculated tip parameters can be used self-consistently for the interpretation of PFM resolution and spectroscopy data, i.e., linear imaging processes.438Scopus© Citations 29 - PublicationInterface and thickness dependent domain switching and stability in Mg doped lithium niobate(American Institute of Physics, 2015-12-08)
; ; ; ; Controlling ferroelectric switching in Mg doped lithium niobate (Mg:LN) is of fundamental importance for optical device and domain wall electronics applications that require precise domain patterns. Stable ferroelectric switching has been previously observed in undoped LN layers above proton exchanged (PE) phases that exhibit reduced polarization, whereas PE layers have been found to inhibit lateral domain growth. Here, Mg doping, which is known to significantly alter ferroelectric switchingproperties including coercive field and switching currents, is shown to inhibit domain nucleation and stability in Mg:LN above buried PE phases that allow for precise ferroelectric patterning via domain growth control. Furthermore, piezoresponse force microscopy(PFM) and switching spectroscopy PFM reveal that the voltage at which polarization switches from the 'up' to the 'down' state increases with increasing thickness in pure Mg:LN, whereas the voltage required for stable back switching to the original 'up' state does not exhibit this thickness dependence. This behavior is consistent with the presence of an internal frozen defect field. The inhibition of domain nucleation above PE interfaces, observed in this study, is a phenomenon that occurs in Mg:LN but not in undoped samples and is mainly ascribed to a remaining frozen polarization in the PE phase that opposes polarization reversal. This reduced frozen depolarization field in the PE phase also influences the depolarization field of the Mg:LN layer above due to the presence of uncompensated polarization charge at the PE-Mg:LN boundary. These alterations in internal electric fields within the sample cause long-range lattice distortions in Mg:LN via electromechanical coupling, which were corroborated with complimentary Raman measurements.485Scopus© Citations 11 - PublicationInfluence of annealing on the photodeposition of silver on periodically poled lithium niobate(American Institute of Physics, 2016-02-07)
; ; ; ; The preferential deposition of metal nanoparticles onto periodically poled lithium niobate surfaces, whereby photogenerated electrons accumulate in accordance with local electric fields and reduce metal ions from solution, is known to depend on the intensity and wavelength of the illumination and the concentration of the solution used. Here, it is shown that for identical deposition conditions (wavelength, intensity, concentration), post-poling annealing for 10 h at 200°C modifies the surface reactivity through the reorientation of internal defect fields. Whereas silver nanoparticles deposit preferentially on the +z domains on unannealed crystals, the deposition occurs preferentially along 180° domain walls for annealed crystals. In neither case is the deposition selective; limited deposition occurs also on the unannealed –z domain surface and on both annealed domain surfaces. The observed behavior is attributed to a relaxation of the poling-induced defect frustration mediated by Li+ ion mobility during annealing, which affects the accumulation of electrons, thereby changing the surface reactivity. The evolution of the defect field with temperature is corroborated using Raman spectroscopy.623Scopus© Citations 10 - PublicationBubble polarization domain patterns in periodically ordered epitaxial ferroelectric nanodot arraysIn this work, bubble polarization domains in periodically ordered ferroelectric Pb(Zr(0.4)Ti(0.6))O(3) nanodot arrays and their formation mechanisms have been investigated by piezoresponse force microscopy (PFM) and Monte-Carlo simulations. The PFM observations reveal the coexistence of single domain and apparent bubble domain patterns within the same nanodot array, which also exhibit dissimilar polarization reversal processes. The formation of various polarization configurations can be accounted for by the interplay of various factors, such as polarization anisotropy and depolarization field. Using Monte-Carlo simulation, we are able to reproduce bubble and single domains and further predict that these patterns can be tailored by varying the nanodot parameters, including dot height, aspect ratio, etc. (C) 2011 American Institute of Physics.
344Scopus© Citations 13 - PublicationElectromechanical imaging of biological systems with sub-10 nm resolutionElectromechanical imaging of tooth dentin and enamel has been performed with sub-10 nm resolution using piezoresponse force microscopy. Characteristic piezoelectric domain size and local protein fiber ordering in dentin have been determined. The shape of a single protein fibril in enamel is visualized in real space and local hysteresis loops are measured. Because of the ubiquitous presence of piezoelectricity in biological systems, this approach is expected to find broad application in high-resolution studies of a wide range of biomaterials. (c) 2005 American Institute of Physics.
427Scopus© Citations 87 - PublicationThickness, humidity, and polarization dependent ferroelectric switching and conductivity in Mg doped lithium niobate(American Institute of Physics, 2015-12-28)
; ; ; ; Mg doped lithium niobate (Mg:LN) exhibits several advantages over undoped LN such as resistance to photorefraction, lower coercive fields, and p-type conductivity that is particularly pronounced at domain walls and opens up a range of applications, e.g., in domain wall electronics. Engineering of precise domain patterns necessitates well founded knowledge of switching kinetics, which can differ significantly from that of undoped LN. In this work, the role of humidity and sample composition in polarization reversal has been investigated under application of the same voltage waveform. Control over domain sizes has been achieved by varying the sample thickness and initial polarization as well as atmospheric conditions. In addition, local introduction of proton exchanged phases allows for inhibition of domain nucleation or destabilization, which can be utilized to modify domain patterns. Polarization dependent current flow, attributed to charged domain walls and band bending, demonstrates the rectifying ability of Mg:LN in combination with suitable metal electrodes that allow for further tailoring of conductivity.432Scopus© Citations 17 - PublicationDirect studies of domain switching dynamics in thin film ferroelectric capacitorsAn experimental approach for direct studies of the polarization reversal mechanism in thin film ferroelectric capacitors based on piezoresponse force microscopy (PFM) in conjunction with pulse switching capabilities is presented. Instant domain configurations developing in a 3x3 mu m(2) capacitor at different stages of the polarization reversal process have been registered using step-by-step switching and subsequent PFM imaging. The developed approach allows direct comparison of experimentally measured microscopic switching behavior with parameters used by phenomenological switching models. It has been found that in the low field regime (just above the threshold value) used in the present study, the mechanism of polarization reversal changes during the switching cycle from the initial nucleation-dominated process to the lateral domain expansion at the later stages. The classical nucleation model of Kolmogorov-Avrami-Ishibashi (KAI) provides reasonable approximation for the nucleation-dominated stage of switching but is inapplicable to the slow switching stage. It has been suggested that the switching dynamics can be approximated by averaging the KAI model over a broad distribution of switching times. (c) 2005 American Institute of Physics.
560Scopus© Citations 211