Piezoresponse force microscopy (PFM) has emerged as a powerful tool to characterize piezoelectric, ferroelectric, and multiferroic materials on the nanometer level. Much of the driving force for the broad adoption of PFM has been the intense research into piezoelectric properties of thin films, nanoparticles, and nanowires of materials as dissimilar as perovskites, nitrides, and polymers. Recent recognition of limitations of single-frequency PFM, notably topography-related cross-talk, has led to development of novel solutions such band-excitation (BE) methods. In parallel, the need for quantitative probing of polarization dynamics has led to emergence of complex time- and voltage spectroscopies, often based on acquisition and analysis of multidimensional datasets. In this perspective, we discuss the recent developments in multidimensional PFM, and offer several examples of spectroscopic techniques that provide new insight into polarization dynamics in ferroelectrics and multiferroics. We further discuss potential extension of PFM for probing ionic phenomena in energy generation and storage materials and devices.

Spatial fluctuations of the microstructure suggest possible self-organized criticality in the Portevin–Le Chatelier plastic instability occurring in age-hardenable alloys. The discontinuous yielding found in a supersaturated Al alloy can be characterized by a universal power-law spectrum that is independent of the experimental conditions. The result provides an explanation for the formation of unexpected detrimental strain localizations when samples are severely deformed, giving a framework for studying the simultaneous effects of solute atoms and precipitates in the decomposition of solid solutions.

Load-bearing, mechanically active tissues are routinely subjected to nonlinear mechanical deformations. Consequently, these tissues exhibit complex mechanical properties and unique tissue organizations. Successful engineering of mechanically active tissues relies on the integration of the mechanical sensing mechanism found in the native tissues into polymeric scaffolds. Intelligent biomaterials that closely mimic the structural organizations and multi-scale responsiveness of the natural extracellular matrices, when strategically combined with multipotent cells and dynamic culture devices that generate physiologically relevant physical forces, will lead to the creation of artificial tissues that are mechanically robust and biologically functional.

Polymeric nanostructures can be synthesized where the catalytic motif is covalently attached within the core domain and protected from the environment by a polymeric shell. Such nanoreactors can be easily recycled, and have shown unique properties when catalyzing reactions under pseudohomogeneous conditions. Many examples of how these catalytic nanostructures can act as nanosized reaction vessels have been reported in the literature. This prospective will focus on the exclusive features observed for these catalytic systems and highlight their potential as enzyme mimics, as well as the importance of further studies to unveil their full potential.

We report a breakthrough in the field of electrolyte additives for use in lithium ion batteries. Batteries containing maleimide (0.1 wt%) as an electrolyte additive absorbed moisture (H2O) from a high-humidity atmosphere. When compared with batteries without the maleimide and absorbed moisture, the capacity of batteries with the “binary additive” showed improvements of 7.4% and 5.2% in a 0.1C/0.1C cycle test, and 394% and 174% in high-power 3C rate tests conducted at room temperature and 55 °C, respectively. Thus, this innovative additive formation can effectively reduce the requirement for anhydrous conditions during the fabrication and operation of lithium ion batteries.

When ultrafine-grained (UFG) samples are deformed plastically, it is necessary to consider the role of grain boundaries even at the micrometer scale in sample size. We report here the occurrence of intensive grain boundary sliding (GBS) at room temperature in micro-pillars of a UFG aluminum alloy having an unusually high strain rate sensitivity. A consequence of this GBS is that the intermittent flow with detrimental strain avalanches characterizing micro-sized conventional crystals is not present in UFG materials, thereby illustrating a potential for effectively applying these UFG materials in micro-devices.

We report on the mechanical and electrical response of VO2 nanowires during the application of uniaxial tensile strain at room temperature. Stress–strain curves exhibit plateaus, which are characteristic of reversible transformations. The mechanical data are also discussed in terms of size effects, which is important for applications where the structural integrity is key to the performance of devices. Electrical measurements during straining show a distinct increase in resistivity at the M1–M2 transition, and a strong piezo-resistive effect for the M2 phase, disclosing new opportunities for future nanostructured devices. To our knowledge, this is the first time that piezoresistivity in the M2 phase has been reported.

The Cu precipitation in a quench-aged high-strength low-alloy steel is studied at the atomic scale by atom probe tomography and high-resolution transmission electron microscopy. The results indicate that the Cu precipitates greatly correlate with carbides in the aspect of distributional character, i.e., the two phases are prone to coprecipitate on the dislocations and/or interfaces (low angle boundaries of the martensite laths). The crystallographic defects have a significant effect on the sizes, morphology and composition of Cu precipitates with Ni and Mn segregation shell.

Nanoindentation-induced phase transformations in both crystalline silicon (c-Si) (100) and ion-implanted amorphous silicon have been studied at temperatures up to 200 °C. The region under the indenter undergoes rapid volume expansion at temperatures above 125 °C during unloading, which is indicated by “bowing” behavior in the load–displacement curve. Polycrystalline Si-I is the predominant end phase for indentation in crystalline silicon whereas high-pressure Si-III/Si-XII phases are the result of indentation in amorphous silicon. We suggest that the Si-II phase is unstable in a c-Si matrix at elevated temperatures and can directly transform to Si-I during the early stages of unloading.

By chemical vapor deposition, aligned single wall carbon nanotubes (SWNTs) and a network of SWNTs are simultaneously grown as the channel and the source–drain electrodes of thin film transistors (TFTs). The increase of aligned SWNTs increases the channel conductance without changing the contact resistance. However, the increase of network-type SWNTs from 19 to 32.5 (SWNTs/μm) decreases the contact resistance fivefold. The contact resistance of all-SWNT TFT is three times lower compared with that of an SWNT TFT using metal electrodes. The all-SWNT TFTs transferred on polyethylene terephthalate (PET) show a transparency of >80% in the visible range of wavelengths.

Recently, we reported on the facile synthesis of a number of two-dimensional early transition metal carbides and nitrides, derived from the MAX phases, that we labeled MXenes. Herein, we report on the electronic and elastic properties—investigated by first principles calculations utilizing the generalized gradient approximation within the density functional theory—of the following two-dimensional transition metal carbides: Ti2C, Ti3C2, Ti4C3, V2C, Cr2C, Zr2C, Hf2C, and Ta2C, Ta3C2, and Ta4C3. Similar to the MAX phases, the MXenes are found to be metallic and possess high elastic moduli when stretched along the basal planes.

We study strain fields and deformation patterns produced by wedge indentation of metals using high-resolution imaging, image correlation and simulation. A long-standing problem associated with simulation of narrow angle wedge indentation is overcome by introducing a weak form of the symmetry boundary conditions. The simulated deformation fields show good agreement with experiment. Based on strain localization, three distinct modes of deformation largely cover the range of wedge angles. Importantly, narrow angle wedge indentation is characterized by intense strain localization at points close to the free surface and thus offers a possible new tool to probe strain gradient effects.

We report on the synthesis of unique tetragonal nanostructures from porous anodic aluminum oxide that enables geometrical three-dimensional (3D) microdesign of the porous surfaces. Scanning electron microscopy study revealed self-organization of hollow oxide nanostructures into hierarchical arrays. The formation of these structures has a localized nature and is associated with local electrical break-down during hard anodization of aluminum in oxalic acid solution. Moreover, in this communication we propose the mechanism of the nucleation and growth of complex 3D structures from porous anodic alumina.

In situ small-angle x-ray scattering (SAXS) is used to investigate the electrochemical durability of Pt-Metal (Pt-M) catalysts sputtered onto nitrogen-modified high surface area carbon powder. The results demonstrate that nitrogen modification promotes catalyst durability through reduction of nanoparticle dissolution and coarsening. Although particle sizes of Pt-M on high surface area carbon supports can be difficult to determine with transmission electron microscopy (TEM), a novel SAXS method has been employed to calculate particle size. SAXS analysis shows that the Pt-M nanoparticle size distribution remained stable for 3000 electrochemical cycles after nitrogen modification, whereas the unmodified support material leads to Pt-M nanoparticle instabilities. These results for industrial-relevant catalyst/support architectures underscore the potential of nitrogen-modified carbon support structures for enhanced Pt-M catalyst durability.

Intrinsic energy resolution in γ-radiation detectors is limited by nonlinear quenching that varies as the second or third power of local excitation density. Using a numerical model for local light yield depending on measured quenching rates, kinetic order, and carrier mobilities, we employ Monte Carlo simulations of energy deposited at each local excitation density to calculate electron energy response that can be directly compared with Compton coincidence and K-dip experiments. Agreement is found for NaI:Tl and SrI2:Eu using thermalized carrier diffusion and linear quenched fraction deduced from total light yield. This lays the groundwork for testing refinements with recent hot-electron extensions of the model.

We observed the formation of dominant shear bands in model ZrCuAl metallic glass (MG) nanowires (18-nm-long) in molecular dynamics simulations, which implies size-independent incipient plasticity in MG materials. The MG nanowires were prepared using the simulated casting technique to ensure proper relaxation of sample surfaces. Under uniaxial compression, shear bands initiate at the surfaces and lead to reduced icosahedral short-range order. The shear band formation is sensitive to sample thermal history, which calls for careful consideration of sample preparation effects in both experimental and numerical studies of size effect in MG samples.

Applying a first-principles computational approach, we study the electronic and charge transport properties of the interfaces between metals and capped carbon nanotubes (CNTs) with various arrangements of topological defects. Observing the length scaling of resistance, we first show that capped CNTs exhibit only one CNT-body-determined low-slope scaling and the resulting very low long-length-limit resistance. The intrinsically low resistance (absence of Schottky-barrier-dominated high-slope scaling) of capped CNTs is next analyzed by the local density of states, which shows the formation of unusual propagating-type metal-induced gap states originating from the topological defect states that are well connected with CNT edge and body states.

Silver nanoparticle inks printed on temperature-sensitive substrates can be converted into structures with high electrical conductivities within fractions of a second by photonic flash sintering. The key principle is the selective heating of the ink by the absorption of strongly focused pulsed light for which the substrate is transparent. The influence of process parameters like intensity and flashing frequency on the sintering speed is investigated. Furthermore, a setup is demonstrated for monitoring the temperature development in an ink during flash sintering, revealing that the substrate's glass transition point is exceeded only for very short time intervals, which prevents deformation.

Ultrafast differential transmission spectroscopy was employed to study the carrier dynamics in InGaN/GaN multiple quantum wells with high inverted hexagonal pits density due to threading dislocation. By monitoring the temporal evolution of the excitonic absorption spectrum, a reduction of the quantum-confinement Stark shift was observed due to the photo-induced in-well field screening at low carrier densities and excitonic absorption quenching at high carrier densities. By comparing the differential absorption spectra at various injected carrier densities, the in-well field screening effect was distinguished from excitonic bleaching.

Novel fluorine-doped zinc tin oxide (ZTO:F) thin-film transistors (TFTs) have been fabricated using an aqueous solution process. Exploiting hydrolysis and condensation reactions in an aqueous solution process, organic-free ZTO:F thin films were fabricated at a low temperature of 250 °C. The fabricated TFT device shows a field-effect mobility of 2.85 cm2/V s, on-to-off current ratios exceeding 107, and sub-threshold swings of 0.83 V/dec. The ZTO:F TFT also displays high operational stability of ΔVth = 1.73 V despite incorporation of a large amount of fluorine and use of a low-temperature annealing process. This is attributed to effective passivation of oxygen vacancy diffusion by metal fluoride bonds at the ZTO:F channel/gate dielectric interface.