Peptide nanotubes based on short dipeptide diphenylalanine (FF) attract a lot of attention due to their unique physical properties ranging from strong piezoelectricity to extraordinary mechanical rigidity. In this work, we present the results of high-resolution Piezoresponse Force Microscopy (PFM) measurements in FF microtubes prepared from the solution. First in-situ temperature measurements show that the effective shear piezoelectric coefficient d15 (proportional to axial polarization) significantly decreases (to about half of the initial value) under heating up to 100 oC. The piezoresponse becomes inhomogeneous over the surface being higher in the center of the tubes. Further, PFM study of a composite consisting of FF microtubes and reduced graphene oxide (rGO) was performed. We show that piezoelectric properties of peptide microtubes are significantly modified and radial (vertical) piezoresponse appears in the presence of rGO as confirmed via PFM analysis. The results are rationalized in terms of molecular approach in which π – π molecular interaction between rGO and dipeptide is responsible for the appearance of radial component of polarization in such hybrid structures.

Since the discovery of the piezoelectric character of bone, the suitability of some piezoelectric materials have been studied for bone repair; they are thought to act like transducers converting the mechanical energy of skeletal deformation in electrical stimuli capable of controlling osteogenic growth. The mechanisms underlying this process are far from being understood and systematic studies at a local scale are required. Atomic force microscopy (AFM) is a unique way to observe phenomena at the nanoscale and liquid imaging provides a unique tool to assess biological phenomena at the nanoscale. So in this study, aiming at a better understanding of the role of piezoelectricity in the osteogenic growth, the interaction between a poled piezoelectric material, in this case poly (L-lactic) acid and an adhesion promoting protein, the fibronectin, and bone-like cells is evaluated by scanning probe microscopy and confocal laser scanning microscopy (CLSM).

The phenomenon of electron tunneling has been known since the advent of quantum mechanics, but continues to enrich our understanding of many fields of physics, as well as creating sub-fields on its own. Spin-dependent tunneling in magnetic tunnel junctions has aroused considerable interest and development. In parallel with this endeavor, recent advances in thin-film ferroelectrics have demonstrated the possibility of achieving stable and switchable ferroelectric polarization in nanometer-thick films. This discovery opened the possibility of using thin-film ferroelectrics as barriers in magnetic tunnel junctions, thus merging the fields of magnetism, ferroelectricity, and spin-polarized transport into an exciting and promising area of novel research. Nowadays, this research has become an important constituent of a broader effort in multiferroic materials and heterostructures that involves rich fundamental science and offers a potential for applications in novel multifunctional devices. The purpose of this article is to review recent developments in ferroelectric and multiferroic tunnel junctions. Starting from the concept of electron tunneling, we first discuss the key properties of magnetic tunnel junctions and then assess key functional characteristics of ferroelectric and multiferroic tunnel junctions. We discuss the recent demonstrations of giant resistive switching observed in ferroelectric tunnel junctions and the new concept of electrically controlling the spin polarization in magnetic tunnel junctions with a ferroelectric tunnel barrier.

No compositional variations of periodically poled lithium niobate (PPLN) (period of ~28 μm) are found using spatially resolved near edge X-ray adsorption fine structure (XANES) spectra taken at the Nb K-edge. The periodicity the ferroelectric domain patterns can be imaged using piezoresponse force microscopy (PFM) and atomic force microscopy (AFM) and the periodic variations in the optical properties of PPLN result in a nonlinear optical response in the IR region at a fixed scattering angle.

Piezoresponse force microscopy (PFM) is a powerful method widely used for nanoscale studies of the electromechanical coupling effect in various materials systems. Here, we review recent progress in this field that demonstrates great potential of PFM for the investigation of static and dynamic properties of ferroelectric domains, nanofabrication and lithography, local functional control, and structural imaging in a variety of inorganic and organic materials, including piezoelectrics, semiconductors, polymers, biomolecules, and biological systems. Future pathways for PFM application in high-density data storage, nanofabrication, and spectroscopy are discussed.

A novel approach for nanoscale imaging and characterization of the orientation dependence of electromechanical properties—vector piezoresponse force microscopy (Vector PFM)—is described. The relationship between local electromechanical response, polarization, piezoelectric constants, and crystallographic orientation is analyzed in detail. The image formation mechanism in vector PFM is discussed. Conditions for complete three-dimensional (3D) reconstruction of the electromechanical response vector and evaluation of the piezoelectric constants from PFM data are set forth. The developed approach can be applied to crystallographic orientation imaging in piezoelectric materials with a spatial resolution below 10 nm. Several approaches for data representation in 2D-PFM and 3D-PFM are presented. The potential of vector PFM for molecular orientation imaging in macroscopically disordered piezoelectric polymers and biological systems is discussed.

The development, operation and applications of a novel continuous chemical reactor system are described. The system, known as a Multiple Stream Mixer/Reactor (or MMR), produces nanoparticles by direct precipitation from two or more reactant solution streams in an extreme energy density, ultraturbulent, collision reaction region. Sensors and a control system are employed to assure constant mixing conditions and desired stoichiometry in the reaction region. The interaction chamber is designed to allow macro-, meso- and micromixing during processing. This allows control of product purity, yield, size, size distribution, and phase purity. Typical nanoparticle diameters in the one to ten nanometer range are often achievable, with tight size distribution. The MMR can be scaled from development quantities to tons/hour for production applications.

Piezoresponse scanning force microscopy (PFM) was applied to study the nanoscale mechanism of retention loss in SrBi2Ta2O9 (SBT) thin films. Experiments were conducted by performing local polarization reversal within an individual grain with subsequent imaging of a resulting domain structure at different time intervals. The retention behavior of the films was studied as a function of switching conditions and electrode material. SFM was also used for nanoscale mapping of leakage current sites and investigation of electrical conduction mechanism at these sites. For the first time, the development of dielectric breakdown in SBT films was directly observed at nanoscale.

The science and technology of ferroelectric thin films is currently attracting worldwide attention because of its application to a new generation of novel devices. Prime, among these applications are nonvolatile ferroelectric random-access memories (NVFRAMs), which have high speed and extended endurance. The core of an NVFRAM is a capacitor with a ferroelectric film sandwiched between two electrode layers. The polarization of the ferroelectric layer in two possible opposite directions, upon application of an electric field between the two electrodes, provides the logic “1” and “0” states needed for binary-code memory. In spite of the advances in the science and technology of ferroelectric thin films and their integration into ferroelectric capacitors, some materials-related integration strategies as well as manufacturability issues have delayed commercialization of NVFRAMs. High-density memories require storage elements that approach submicron lateral dimensions. Thus, improved understanding of the materials properties and polarization phenomena is needed in conjunction with the development of new characterization tools that can enable such an understanding. For example, a fundamental issue in ferroelectric thin-film capacitors is the exact nature of the complex domain structure in the polarizable ferroelectric layer and its dynamics under high-speed switching conditions. The miniaturization of NVFRAMs requires understanding of granularity in polarization reversal dynamics, fatigue, and retention characteristics. In this respect, theoretical models and electrical measurements (e.g., polarization hysteresis loops and transient currents) have provided substantial insights into the nature of the switching processes. However, the models (phenomenological in nature) and the electrical measurements provide only a global or macroscopic view of the switching process.

Scanning force microscopy (SFM) was applied to direct nanoscale investigation of the mechanism of retention loss in ferroelectric thin films. Experiments were conducted by performing local polarization reversal within an individual grain with subsequent imaging of a resulting domain structure at various time intervals. A conductive SFM tip was used for domain switching and imaging in the SFM piezoresponse mode.

Crystallization behavior, defects, and interface structures of sol-gel derived LiNbO3 films on three kinds of substrates were examined. The nucleation was found to occur epitaxially at the interface between the film and the substrate. The continuous film is formed by coalescence of the island-like crystallites. When sapphire substrate is used, which has large lattice mismatch with the LiNbO3, the resulting film contains a large amount of micropores, twin structures, and misfit dislocations. On the other hand, while LiTaO3 and 5% MgO-doped LiNbO3 substrates with smaller mismatch are used as substrates, the films show no evidence of the formation of dislocations and twins. The film on 5% MgO-doped LiNbO3 substrate shows better optical waveguiding property.

An atomic force microscope is used for visualization and control of domain structure in the ferroelectric crystal guanidinium aluminum sulfate hexahydrate (GASH). Large built-in domains are delineated due to the tip-sample electrostatic interaction by the force microscope operating in friction mode. It is found that an applied voltage of a particular sign created new domains whereas a potential of opposite sign erased these domains. Domains created by an external electric field are visualised in topography mode due to piezoelectric deformation of the crystal. The dynamics of domain lateral growth has been directly observed with nanoscale resolution.