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Switchable tribological properties of ferroelectrics offer an alternative route to visualize and control ferroelectric domains. Here, we observe the switchable friction and wear behavior of ferroelectrics using a nanoscale scanning probe—down domains have lower friction coefficients and show slower wear rates than up domains and can be used as smart masks. This asymmetry is enabled by flexoelectrically coupled polarization in the up and down domains under a sufficiently high contact force. Moreover, we determine that this polarization-sensitive tribological asymmetry is widely applicable across various ferroelectrics with different chemical compositions and crystalline symmetry. Finally, using this switchable tribology and multi-pass patterning with a domain-based dynamic smart mask, we demonstrate three-dimensional nanostructuring exploiting the asymmetric wear rates of up and down domains, which can, furthermore, be scaled up to technologically relevant (mm–cm) size. These findings demonstrate that ferroelectrics are electrically tunable tribological materials at the nanoscale for versatile applications. The interaction of flexoelectric polarization arising from strain gradients with ferroelectricity impacts tribological properties and facilitates fine physical lithography without masks or chemicals, with potential applications in various fields. [ABSTRACT FROM AUTHOR]

The well‐known ferromagnetic oxide, NiFe2O4, was studied as a potential candidate for room‐temperature Type II magnetoelectrics. A spin canting as one of the essential requirements for Type II multiferroics was induced by breaking the stoichiometry, that is, intentionally subtracting Fe ions. We observed that Fe ions were first subtracted exclusively from the tetrahedral sites, leading to an increase in the magnetoelectric coupling owing to an increasing degree of spin canting. The enhancement in the magnetoelectric coupling culminated beyond the subtraction level of ~30 at.%, at which Fe ions started to be removed from the octahedral sites. Alongside, we observed that the subtraction of Fe ions gives rise to a ferroelectricity due to the formation of defect complexes that establish an internal bias field. [ABSTRACT FROM AUTHOR]

Ferroelectricity in HfO2 thin films can be utilized for fast, power‐efficient, and highly scalable non‐volatile memories. However, the required wake‐up process for inducing ferroelectricity/ achieving higher polarization is one of the major hurdles that hinder HfO2‐based thin films from developing reliable electronic devices. The wake‐up effect is believed to originate from i) phase transformation from non‐ferroelectric to ferroelectric, ii) movement of defect entities (mainly oxygen vacancy defects) near the film‐electrode interface, and iii) heterogeneity of the electrode interfaces. In the present study, an experimental strategy is designed to overcome these sources of the wake‐up process. A multi‐step deposition and annealing process is carried out to induce wake‐up‐free ferroelectricity in Yttrium doped HfO2 (Y:HfO2) thin film directly grown on Si‐substrate. Furnace annealing is utilized instead of the standard rapid thermal annealing process to reduce the oxygen deficiencies and stimulate the direct growth of the polar Y:HfO2. The oxygen‐vacancy‐related defects are found to be the dominating source of wake‐up effect in Y‐doped HfO2 films. The step‐wise deposition and annealing in the oxygen atmosphere facilitate direct growth of the polar phase, reduce the oxygen vacancies, and induce wake‐up‐free ferroelectricity in Y:HfO2. [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]

A highly scalable synapse device based on a junctionless (JL) ferroelectric (FE) FinFET is presented for neuromorphic applications. The synaptic behaviors of the JL metal-ferroelectric-insulator-silicon FinFET were experimentally demonstrated after verifying the ferroelectric characteristics of the HfZrOX (HZO) film using a metal-ferroelectric-metal capacitor. The fabricated synapse showed distinguishable polarization switching behaviors with gradually controllable channel conductance. From neural network simulations using the proposed JL FE FinFET as synapses, the pattern recognition accuracy for hand-written digits was validated to be approximately 80% for neuromorphic applications. [ABSTRACT FROM AUTHOR]

Here, we demonstrate a novel process to convert TiO2 nanotubes into ferroelectric nanohoneycombs, comprised of vertically aligned PbTiO3 nanotubes. Tube bottom opening process enabled effective infiltration of lead acetate precursor into the nanotubes. Nanohoneycombs, which were converted via additional lead supplement process, showed uniform conversion and well-defined ferroelectric properties with the effective piezoelectric coefficient of approximately 20 pm/V, which was measured by piezoresponse force microscopy. [ABSTRACT FROM AUTHOR]

Nanoscale ferroelectric honeycombs, comprised of vertically aligned PbTiO3 nanotubes, are fabricated by vapor phase reaction between lead acetate-infiltrated TiO2 nanotubes and PbO vapor. PbTiO3 nanohoneycombs converted by vapor phase reaction at 550°C showed well-aligned nanoscale structure with alignment angle less than 1° and well-defined ferroelectric properties with the effective piezoelectric coefficient of 44 pm/V. This novel nanoscale structure is expected to facilitate high efficiency sensing of electromechanical and electrochemical stimuli. [ABSTRACT FROM AUTHOR]

Information storage system that has a potentially ultrahigh storage density based on the principles of atomic force microscopy (AFM) has been developed. Micro-electro-mechanical systems (MEMS) technology plays a major role in integration and miniaturization of the standard AFM. Its potential application for ultrahigh storage density has been demonstrated by AFM with a piezoresponse mode to write and read information bits in ferroelectric Pb(ZrxTi1−x)O3 films. With this technique, bits as small as 40 nm in diameter have been achieved, resulting in a data storage density of simply more than 200 Gb/in2. Retention loss phenomenon has also been observed and investigated by AFM in the piezoresponse mode. Finally, local piezoelectric measurements of PZT films by different processing technologies are discussed in detail. [Copyright &y& Elsevier]

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]

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]

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]

[Display omitted] • The effects of hydrophobicity and ferroelectricity of artificial SEIs were investigated. • Spin-coated P(VDF-TrFE) layer on a zinc metal anode inhibits zinc dendrite growth and side reactions. • The uniform Zn plating achieved by the P(VDF-TrFE) layer inhibits zinc dendrite growth. • Both symmetrical cells and Zn/MnO 2 full cells with P(VDF-TrFE)-coated Zn show stable electrochemical performance. Zn anodes are highly promising aqueous battery materials due to their abundant sources, environmental friendliness, and high theoretical capacity of 820 mAh/g. Nevertheless, Zn undergoes dendritic growth and side reactions in mildly acidic electrolytes, leading to shorter cycling lifetimes. Herein, a layer of poly(vinylidene fluoride- co -trifluoroethylene) (P(VDF-TrFE)) was spin-coated onto a Zn anode to address this issue. The coated layer physically and electrically blocked contact between the Zn surface and the electrolyte due to its hydrophobic nature. Additionally, the ferroelectric properties of crystalline P(VDF-TrFE) (c-P(VDF-TrFE)) facilitated mass transport and homogenized the electric field, resulting in consistent plating and stripping of Zn ions beneath the film. As a result, the c-P(VDF-TrFE) coating on the Zn symmetric cell led to a stable overpotential (<40 mV) and long cycling lifetimes of more than 350 h (1 mA cm−2, 0.5 mAh cm−2). Even with current conditions of 5 mA cm−2 and 0.5 mAh cm−2, the c-P(VDF-TrFE)-coated Zn symmetric cell demonstrated stable operation for over 600 h. Furthermore, a Zn||MnO 2 full cell exhibited high capacity retention after 1000 cycles. [ABSTRACT FROM AUTHOR]