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.

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.

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.

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.

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.

We report an easy way to assemble porous one-dimensional (1D) Ni2P nanowires through phosphatization of a Ni(SO4)0.3(OH)1.4 nanobelt precursor. The peculiar synthetic process endows the Ni2P nanowires with large surface area, hierarchical porous structure and the ability to form closely connected network for transporting both electrons and electrolytes, which in conjunction with the high intrinsic electrocatalytic activity make it an excellent low-cost counter electrode material for dye-sensitized solar cells (DSSCs). Indeed, the first investigation of such novel counter electrode for DSSC presented superb photovoltaic performance rivaling the conventional Pt counter electrode.

A quantitative correlation between R-line luminescence at around 1.37 µm and {311} defect nature, size and concentration has been undertaken in silicon, following keV Si-implantation and subsequent annealing using photoluminescence spectroscopy and plan-view transmission electron microscopy. The formation and evolution of the rod-like defects were found to be dependent on annealing time at a temperature of 700 °C, but there was no simple correlation found between the density and size of those defects and the R-line intensity. In particular, whereas the presence of {311} defects is essential for observing R-line luminescence, both very small {311} defects at short annealing times and fully developed {311} defects at long annealing times do not contribute to such luminescence. We provide possible explanations for this behavior and suggest that the local (strain) environment around defects, the dopant level and impurities in the silicon substrate may all play a role in determining R-line intensity.

Quantum simulations of oxygen incorporation at a Σ5 grain boundary in yttria-stabilized zirconia (YSZ), a common solid oxide fuel cells (SOFCs) electrolyte, show that the incorporation energy is reduced compared with YSZ with no grain boundaries. The simulation results are supported by electrochemical impedance spectroscopy (EIS) measurements conducted on a single crystalline YSZ substrate with nanogranular interlayered YSZ. EIS results showed that single crystalline YSZ membranes with nanogranular surface (i.e., high grain boundary densities) exhibit small electrode impedances than the reference single crystalline YSZ. The 20-nm-thick nanogranular YSZ interlayer was fabricated by atomic layer deposition and the performance for SOFCs with nanograined interlayer was increased by factor of 2 at operating temperatures between 350 and 450 °C.

Biogenic minerals often contain inorganic and organic impurities that are believed to harden and toughen the material. However, because of the complexity of these systems, it is difficult to deconvolute the effect of each of these impurities on the hardness of the material. We have created single-crystal samples with a range of magnesium concentrations and measured their hardness while controlling for orientation. We find that hardness increases linearly with magnesium content and that magnesium impurities could account for ~20% of the increased hardness in biogenic calcite from the mollusk Atrina rigida when compared with pure geologic calcite.