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Piezoresponse force microscopy (PFM) has been widely used for the nanoscale analysis of piezoelectric properties and ferroelectric domains. Although PFM is useful because of its simple and nondestructive features, PFM measurements can be obscured by non-piezoelectric effects that could affect the PFM signals or lead to ferroelectric-like behaviors in non-ferroelectric materials. Many research studies have addressed related technical issues, but they have primarily focused on vertical PFM. Here, we investigate significant discrepancies in lateral PFM signals between the trace and the retrace scans, which are proportional to the scan angle and the cantilever lateral tilting discrepancy. The discrepancies in PFM signals are analyzed based on intrinsic and extrinsic components, including out-of-plane piezoresponse, electrostatic force, and other factors. Our research will contribute to the accurate PFM measurements for the visualization of ferroelectric in-plane polarization distributions. [ABSTRACT FROM AUTHOR]

This study investigates the impact of resonant acoustic powder mixing on the delay time of the W–KClO4–BaCrO4 (WKB) mixture and its potential implications for powder and material synthesis. Through thermal analysis, an inverse linear relationship was found between thermal conductivity and delay time, allowing us to use thermal conductivity as a reliable proxy for delay time. By comparing the thermal conductivity of WKB mixtures mixed manually and using an acoustic powder mixer, we found that acoustic powder mixing resulted in minimal deviations in thermal conductivity, proving more uniform mixing. Furthermore, differential scanning calorimeter analysis and Sestak–Berggren modeling demonstrated consistent reaction dynamics with a constant activation energy as the reaction progressed in samples mixed using acoustic waves. These findings underscore the critical role of uniform powder mixing in enhancing the thermodynamic quality of the WKB mixture and emphasize the importance of developing novel methods for powder and material synthesis. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HAp), a main constituent of the cortical bone, retains a large surface charge that plays a critical role in the regeneration of bones, whose source remains an enigma. Here, we used multi-eigenmode piezoresponse force microscopy via Pearson correlation and conducted multiscale material analysis to independently measure the piezoelectric coefficient and the surface charge density of HAp. Quantitative comparison was conducted between the measured surface charge density and the conceptual values computed for all possible candidates of the surface charging such as piezoelectricity, chemically induced surface charging, flexoelectricity, and defect dipole moment. The results presented Ca2+ ions released during local calcium orthophosphate phase transition at the surface as the main source of the surface charging. Further analysis showed that the ion concentration was modulable using a charged conductive tip, implying that the interstitial ions are mobile within the HAp matrix. In this work, we developed a novel method to measure the effective surface charge density of arbitrary material systems, thereby facilitating the investigation of biophysical phenomena related to surface electromechanics. Most importantly, the research promotes a new understanding of the origin of osteoconduction observed in past works conducted on HAp. [ABSTRACT FROM AUTHOR]

Piezoresponse force microscopy (PFM) uses a cantilever arm to track the electromechanical motion of the electric dipole moment to visualize the ferroelectric domain structure, which provides an important insight into the physics of switchable electric polarization—especially for memory devices and integrated microelectronics. Here, I provide a tutorial on single frequency vertical PFM, the most basic mode of PFM. I will start with the basic components of atomic force microscopy (AFM), including tip, cantilever, X–Y stage, Z actuator, and lock-in amplifier. Contact mode AFM will be briefly explained and discussed, where you can find two modes: constant deflection and constant height modes. Single-frequency vertical PFM splits the frequency domain of tip vibration into low and high frequencies and uses a low-pass filter to nullify any motion caused by topography (constant deflection). In contrast, the lock-in amplifier will pinpoint the vibration induced by the vertical piezoelectric strain along the sample's surface normal (constant height). This tutorial will provide an overall and detailed step by step instruction to conduct PFM imaging and piezoresponse hysteresis loop measurement using atomic force microscopy and a lock-in amplifier and teach how to interpret the PFM images and the piezoresponse hysteresis loops for various applications. [ABSTRACT FROM AUTHOR]

Section VI, page 7, paragraph 1, "...we get SB 0 sb = 587.1 I i C/cm SP 2 sp , which is remarkably close to the surface charge density given by our measurement = 530.2 ± 26.5 I i C/cm SP 2 sp ." should be changed to "we get SB 0 sb = 581.4 I i C/cm SP 2 sp , which is precisely within range of the surface charge density given by our measurement = 602.5 ± 37.7 I i C/cm SP 2 sp ." As such, the following change must be made to all related values: Section VI, page 7, paragraph 1, "L SB P sb = 14.97 nm" should be changed to "L SB P sb = 14.73 nm." Section VII, page 8, paragraph 2, " L SB P sb /L SB 0 sb = 0.6202" should be changed to " L SB P sb / L SB 0 sb = 0.6105.". [Extracted from the article]

Multiferroic nanocomposites, consisting of branched, ferrimagnetic CoFe2O4 filaments and large protruding PbTiO3 particles embedded in a piezoelectric PbTiO3 matrix, have been fabricated by co-deposition using metalorganic chemical vapor deposition. Branched CoFe2O4 filaments reduce the CoFe2O4/PbTiO3 interfacial strain and induce a perpendicular magnetic anisotropy. Three-dimensional characterizations reveal that in addition to the c-domain, grains with a second orientation in PbTiO3 particles contribute to an additional four apparent variants of polarization. In contrast, the PbTiO3 matrix exhibits only c-domain polarization with a smaller magnitude. The smaller piezoresponse results from the constraints imposed by the branched CoFe2O4 filaments. Three-dimensional microstructure and property analysis provide a comprehensive insight on the structure-property relationship of multiferroic nanocomposites grown by metalorganic chemical vapor deposition. [ABSTRACT FROM AUTHOR]

A 17 nm thick PbTiO3 (PTO) films were fabricated via PbO gas phase reaction with TiO2 starting layer in a sputtering chamber. The influence of deposition temperature of TiO2 on the piezoelectric properties of PTO thin films was investigated. The remnant piezoresponse of PTO films nonlinearly increased as a function of TiO2 deposition temperature, which is correlated with the increase in average grain diameter of PTO film. As grain size increases, the restriction on remnant piezoresponse imposed by the grain boundary via coupling between local strain and polarization becomes less pronounced, which results in the increase in remnant piezoresponse. Furthermore, we found that the vertical shift in piezoresponse hysteresis loops is closely related to the residual stress state. A strong correlation between the negative vertical shift and the residual tensile stress reveals that residual stress on the resulting PTO film contributed to the asymmetric piezoelectric property. [ABSTRACT FROM AUTHOR]

We have studied the effect of local surface potential distribution on its relaxation in the polycrystalline ferroelectric thin films. A lower surface potential region, i.e., potential pit, is generated near a grain boundary. The deep potential pit has a faster relaxation than the area far away from the potential pit due to the acceleration of the screen charge draining near the grain boundary and the domains formed by applying higher voltage have a faster relaxation due to the larger gradient of screen charge distribution. In addition, the surface potential and its relaxation depend on the sign of applying voltage. The result shows that the surface potential distribution may influence significantly to the reliability of bit signal on the memory devices. [ABSTRACT FROM AUTHOR]

We report the dependence of the ferroelectric domain configuration and switching behavior on the shape (square versus round) of epitaxial BiFeO3 (BFO) nanostructures. We fabricated (001) oriented BFO(120 nm)/SrRuO3(SRO,125 nm) film layers on (001) SrTiO3 single crystals by rf magnetron sputter deposition, and patterned them to square (500×500 nm2) and round (502 nm in diameter) shaped nanostructures by focused ion-beam lithography. The surface morphology and the crystalline structure of the nanostructures were characterized by scanning electron microscopy and x-ray diffraction, respectively, while the domain configuration was investigated using piezoelectric force microscopy. We found that the square-shaped nanostructures exhibit a single variant domain configuration aligned along the [111] direction, whereas the round-shaped nanostructures exhibit seven variants of domain configuration along the [111], [111], [111], [111], [111], [111], and [111] directions. Moreover, local d33 piezoelectric coefficient measurements showed hysteresis loops with a strong displacement in the voltage axis (strong imprint) for the square-shaped nanostructures, while the round-shaped ones exhibited more symmetric loops. These findings have critical implications for the development of nanocapacitors for gigabyte to terabyte nonvolatile ferroelectric memories. [ABSTRACT FROM AUTHOR]

Pb(Zr[sub 0.52]Ti[sub 0.48])O[sub 3] (PZT) thin films were fabricated on Pt( 111)/TiO[sub x]/SiO[sub 2]/Si substrates at 375°C by radio frequency magnetron sputtering. A mixture of (110) and (100) orientations was found in all the PZT thin films. However, the in-plane grain size increased with an increase in film thickness, all films had smooth surfaces, and the root mean square roughness of the PZT films was in the range of 1-1.5 nm. As the film thickness increased, a decrease in residual stress and volume density of the PZT films was observed. PZT films become poorly crystallized with a decrease in film thickness. The magnitude of the maximum displacement from atomic force microscopy in local piezoresponse hysteresis mode increased from 187.25 ± 9.363 in 40 nm to 418.5 ± 20.925 in 152 nm. We suggest that the degradation in piezoelectric properties with a decrease in film thickness resulted from degradation of the crystallinity observed using transmission electron microscopy analysis, size effects derived from the grain size, and the residual stress evaluated using a laser reflectance method. [ABSTRACT FROM AUTHOR]

The contrast mechanisms of domain imaging experiments assisted by atomic force microscope (AFM) have been investigated by model experiments on nonpiezoelectric (silicon oxide) and piezoelectric [Pb(Zr,Ti)O[sub 3]] thin films. The first step was to identify the electrostatic charge effects between the tip, the cantilever, and the sample surface. The second step was to explore the tip-sample piezoelectric force interaction. The static deflection of the cantilever was measured as a function of dc bias voltage (V[sub dc]) applied to the bottom electrode (n-type Si wafers) for noncontact and contact modes. In addition, a small ac voltage (V[sub ac] sin ωt) was applied to the tip to measure the amplitude (A[sub ω]) and phase (Φ[sub ω]) of the first harmonic (ω) signal as a function of V[sub dc]. By changing from the noncontact to the contact mode, a repulsive contribution to the static deflection was found in addition to the attractive one and a 180° phase shift in Φ[sub ω] was observed. These results imply that in the contact mode the cantilever buckling is induced by the capacitive force between the cantilever and the sample surface. This interaction adds to the tip-sample piezoelectric interaction thereby overlapping the obtained tip vibration signal. Therefore, the antiparallel ferroelectric domain images obtained at zero dc bias voltage will show a variation in A[sub ω] but a negligible one in Φ[sub ω]. The capacitive force contribution to the tip vibration signal was further verified in piezoelectric hysteresis loop measurement assisted by the AFM. The observed vertical offset of the loops was explained by the contact potential difference between the cantilever and the bottom electrode. The shape of the curve could be explained by the capacitive force interaction combined with the tip-sample piezoelectric interaction. The experimental results obtained in this study support the interpretation of the ... [ABSTRACT FROM AUTHOR]

(c) A simple topography composed of two sinusoidal components where the red curve represents the high frequency variation in topography whereas the blue curve represents the low frequency one. (b) The temporal evolution of AFM tip vibration during the scan shown in (a). (d) Temporal evolution plots of AFM tip vibration for low-frequency and high-frequency components. [Extracted from the article]

Presents a study which focused on YBa[sub2]Cu[sub3]O[sub7-x] superconductor thin films, which were deposited on LaAlO[sub3](100) single crystal substrates using a metalorganic chemical vapor deposition method. Condition in which the critical characteristics of the bridge-type junctions decreased; Description of an X-ray diffraction pattern of thin films deposited on the single crystal substrate; Composition of the diffraction pattern.

We investigated the surface potential of TiO2 single crystals using scanning probe microscopy (SPM) under different gas environment. The SPM tip-induced electrical stress resulted in reversal in the surface potential, Vsurf, polarity only in H2/Ar (ΔVsurf = 0.30 eV) and not in Ar and O2. Quantitative measurement of the influence of ambient gas on the surface potential led us to develop a model where the adsorbed oxygen molecules and oxygen vacancies interact to change their relative concentration leading to different surface potential in TiO2. These results will give us insights into ambient-dependent physical phenomena in oxide thin film nanostructures. [ABSTRACT FROM AUTHOR]

Mechanical behavior of micron-scale cantilevers with a distributed, flexible proof mass is investigated to understand proof mass size effects on the performance of microelectromechanical system energy harvesters. Single-crystal silicon beams with proof masses of various lengths were fabricated using focused ion beam milling and tested using atomic force microscopy. Comparison of three different modeling results with measured data reveals that a 'two-beam' method has the most accurate predictive capability in terms of both resonant frequency and strain. Accurate strain prediction is essential because energy harvested scales with strain squared and maximum strain will be a design limit in fatigue. [ABSTRACT FROM AUTHOR]

A simple quantitative measurement procedure of in-plane cantilever torsion for calibrating lateral piezoresponse force microscopy is presented. This technique enables one to determine the corresponding lateral inverse optical lever sensitivity (LIOLS) of the cantilever on the given sample. Piezoelectric coefficient, d31 of BaTiO3 single crystal (-81.62 ± 40.22 pm/V) which was calculated using the estimated LIOLS was in good agreement with the reported value in literature. [ABSTRACT FROM AUTHOR]

We investigated the effect of charged domain boundaries (CDBs) on the coercive voltage (Vc) in polycrystalline Pb(Zr0.25Ti0.75)O3 (PZT) thin films using angle-resolved piezoresponse force microscopy (AR-PFM). By using the AR-PFM technique, we could observe the detailed domain structure with various degrees of CDBs including neutral domain boundaries in the PZT thin films. We found that the Vc increases at CDBs induced by polarization discontinuities. We attribute the change in Vc to the built-in field created by uncompensated polarization charges at the CDBs in the PZT thin films. [ABSTRACT FROM AUTHOR]

Here, we present a direct observation of fatigue phenomena in epitaxially grown Pb(Zr0.2Ti0.8)O3 (PZT) thin films using second harmonic piezoresponse force microscopy (SH-PFM). We observed strong correlation between the SH-PFM amplitude and phase signals with the remnant piezoresponse at different switching cycles. The SH-PFM results indicate that the average fraction of switchable domains decreases globally and the phase delays of polarization switching differ locally. In addition, we found that the fatigue developed uniformly over the whole area without developing region-by-region suppression of switchable polarization as in polycrystalline PZT thin films. [ABSTRACT FROM AUTHOR]

We report an elastic relaxation and increase in local strain variation correlated with ferroelectric domains within epitaxial BiFeO3 thin film nanostructures fabricated by combined electron-beam and focused ion-beam nanolithography. Nano-focused x-ray diffraction microscopy provided new insights into the relationship between film strain and ferroelectric domains in nanostructures, namely: (i) an out-of-plane (C-axis) elastic relaxation of as much as -1.8% Δc/c in a BFO film-based nanostructure relative to the planar film lattice constant; (ii) an out-of-plane rotation trending from the center towards all released edges of the nanostructure; and (iii) an increase of inter-domain strain variation within the nanostructure of approximately 10 times the inter-domain variation found within the planar film, correlated with ferroelectric domain boundaries as confirmed by piezoresponse-force microscopy. These results indicate that the release of in-plane BFO/SRO mismatch strain in a planar film is taken up by the local ferroelectric domain structure after patterning, resulting in greatly increased mechanical strain gradients within the structure. [ABSTRACT FROM AUTHOR]

Here we introduce angle-resolved piezoresponse force microscopy (AR-PFM), whereby the sample is rotated by 30° increments around the surface normal vector and the in-plane PFM phase signals are collected at each angle. We obtained the AR-PFM images of BaTiO3 single crystal and cube-on-cube epitaxial (001) BiFeO3 (BFO) thin film on SrRuO3/SrTiO3 substrate, and confirmed that the AR-PFM provides more unambiguous information on the in-plane polarization directions than the conventional PFM method. Moreover, we found eight additional in-plane polarization variants in epitaxial BFO thin films, which are formed to mitigate highly unstable charged domain boundaries. [ABSTRACT FROM AUTHOR]

Systematic studies are presented on the effects of cantilever buckling in vector piezoresponse force microscopy (V-PFM) imaging of polarization domains in thin-film based (001)-oriented BiFeO3 nanostructures, as observed through the coupling of out-of-plane and in-plane PFM images. This effect is a strong function of the laser spot position on the cantilever, being strongest at the free end, and insignificant at 60% of the cantilever length from the pivot point. This finding provides a unique approach to V-PFM imaging of ferroelectric polarization domains, yielding three dimensional PFM images without sample rotation in the plane. [ABSTRACT FROM AUTHOR]

Using Kelvin force microscopy, the authors have investigated the potential distribution on ferroelectric films. The local distribution of potential was observed on downward, prepoled areas. The polarity of the potential corresponds to the screen charge. It was found that the electrical properties of the grain boundary affect the potential distribution. Most of the grain boundaries show a lower potential than the area inside the grain. The authors identified certain regions at the grain boundary with a very low potential. Such potential pits may act as efficient screen charge draining paths and may lead to important perturbations on the device level. [ABSTRACT FROM AUTHOR]

The authors have investigated the polarization reversal on ferroelectric thin films caused by a grounded tip on 50-nm-thick Pb(Zr,Ti)O3 films. Backswitching occurred when the grounded tip recontacted a “freshly” switched area. It is believed that the upper part of the film switches back due to the field between the grounded tip and previously injected charges. During dynamic operation, partial backswitching was observed during pulsed writing using pulse widths of 1 ms. The results show that polarization reversal is an issue, which has to be addressed in the writing scheme of future probe-based storage devices. [ABSTRACT FROM AUTHOR]

We studied polarization switching of 295 nm thick 〈111〉-oriented-Pb(Zr[SUB0.45]Ti[SUB0.55])O[SUB3] (PZT) thin-film capacitors through a polarization hysteresis loop and piezoelectric force microscopy (PFM) on top of the Pt electrode. Positive voltage pulses of 450 kV/cm and 2.5 ms were applied to the top as a poling pulse. Negative pulses ranging from -45 to -60 kV/cm at an interval of 3 kV/cm were applied to the top electrode. After each pulse, we performed PFM imaging by applying 17 kHz ac voltage of 1 V peak to peak to the bottom electrode while grounding the top one and the tip. The first-harmonic amplitude and phase of the tip vibration signal were mapped over the scanned area of 10 × 10μm[SUP2]. Subsequently, we measured the polarization hysteresis curve at 100 Hz after each domain image acquisition to estimate the volume fraction of switched polarization induced by the positive voltage pulses. We analyzed the areal fraction of switched domains as a function of pulse voltage from phase images and compared it with the volume fraction obtained from the hysteresis loops. Based on the evolution of domain images and the comparison plots of the areal and volume fractions of switched domains, we conclude that forward domain growth is a rate-limiting step during polarization reversal in 〈111〉-oriented-PZT thin-film capacitors. [ABSTRACT FROM AUTHOR]

We introduce a method to investigate the domain stability issue based on piezoresponse microscopy. The switching and back-switching processes of sol-gel derived (Pb[sub 0.76]Ca[sub 0.24])TiO[sub 3] thin films were investigated by comparing the local piezoelectric hysteresis loops in continuous mode and pulse mode. It was found that the local hysteresis loops acquired by the pulse mode in shorter pulse width were dominated by the back-switching process while the continuous mode piezoelectric hysteresis loop provides information on the domain switching process. [ABSTRACT FROM AUTHOR]

Direct observation of polarization distribution at nanoscale by scanning force microscopy across partially etched Pb(Zr, Ti)O[sub 3] film ferroelectric capacitors with size 2 × 3 µm and preferential orientation (111) has revealed an anomalous polarization pattern characterized by polarization inversion in the center of the capacitor. This self-structured pattern is reproducible and independent on the spontaneous polarization orientation, but strongly influenced by the film texture and capacitor size. In particular, capacitors of the same texture with size 0.5 × 0.5 µm as well as capacitors with (100) preferential orientation of any size did not exhibit such anomalous polarization distribution. A tentative explanation consistent with the essential features of the observed polarization behavior in terms of strain-induced phase transition is discussed. [ABSTRACT FROM AUTHOR]

We performed piezoelectric force microscopy (PFM) measurements on arrays of poled nanosize domains in 150 nm thick (111) preferentially oriented Pb(Zr[sub 0.4]Ti[sub 0.6])O[sub 3] films grown by chemical solution deposition. Each domain of arrays was characterized by dot, egg, and ring structures depending on the pulse width ranging from 1 to 5 ms. The PFM measurements were followed by heat treatments at successively higher temperatures of 100 °C, 130 °C, and 160 °C for 30 min with rapid cooling down to room temperature before each measurement. The retention loss phenomena of the bits were characterized by measuring the number and dimension change of the remaining data bits. It was concluded that the ring-structured bit arrays, which represent fully penetrating domains through the film thickness, were the most stable form in terms of retention loss characteristics. [ABSTRACT FROM AUTHOR]

We report visualization of three-dimensional domain structures in ferroelectric PbTiO3 (PTO) nanotubes (NTs) using piezoresponse force microscopy (PFM). The domain distributions of the x, y, and z-axes in PTO NTs were separately measured out-of and in-planes at angles of 0° and 90° by vertical and lateral PFM. The separately obtained PFM images were combined to reconstruct the complex domain structures based on some basic assumptions and finite element modeling. The cross-sectional domain configurations of the PTO NTs were visualized by the proposed approach. The results can provide insight into complex domain configurations of ferroelectric nanostructures. [ABSTRACT FROM AUTHOR]

A correction to the article "Direct observation of fatigue in epitaxially grown Pb(Zr, Ti)O3 thin films using second harmonic piezoresponse force microscopy," that was published in the 2010 issue is presented.

The size, shape, and polarization orientation of fatigued areas formed during the suppression of the switchable polarization (P[sub r][sup s]) (fatigue) in Pt–PZT–Pt ferroelectric capacitors (FECAPs), were observed by means of atomic force microscopy and by imaging the phase of the piezoelectric vibration induced by a low ac field applied between the top and bottom electrodes. In the virgin state (FECAP as prepared), the pattern of the polarization domains with opposite orientation was randomly distributed with typical sizes of 1–3 μm. The application of a dc field larger than the coercive field (E[sub c]) enabled to fully orient the polarization of the regions in either directions. During the initial fatigue (<35% of suppressed P[sub r][sup s]), polarized regions with frozen orientation and size ranging between 100 nm and 1 μm became visible. In the fatigued state (>65% of suppressed P[sub r][sup s]), two main configurations of the frozen polarization domains were distinguished. One was characterized by a strong preferential direction (top to bottom electrode) and the other by randomly distributed regions of opposite oriented frozen polarization. The degrees of fatigue obtained by analyzing the vibration phase images are in good agreement with those obtained by standard polarization measurements. It is concluded that the P[sub r][sup s] suppression (fatigue) is due to “region by region” or “grain by grain” freezing of P[sub r][sup s] and that the frozen P[sub r][sup s] can have a preferential orientation. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]