We have studied the effects of focused-ion-beam (FIB) irradiation and prestraining on the mechanical properties of nearly defect-free Au microparticles on a sapphire substrate. The Au microparticles, which were produced by a solid-state diffusion dewetting technique, were FIB-irradiated and/or prestrained, the latter using a nanoindenter with a flat ended punch operating under a nanohammering mode. Also, the prestrained Au microparticles were exposed to FIB to examine the effects of ion-beam damage on the properties of crystals containing mobile dislocations. We found that both FIB irradiation and prestraining reduced the yield strength of pristine Au microparticles significantly and made the stress–strain curves jerky. However, FIB irradiation does not affect the mechanical properties of prestrained Au microparticles very significantly. Once a microparticle contains mobile dislocations, its mechanical properties are not influenced much by the defects generated by FIB irradiation, even at the submicrometer scale.

Despite extensive research, the understanding of the fundamental processes governing yielding and plastic flow in metallic glasses remains poor. This is due to experimental difficulties in capturing plastic flow as a result of a strong localization in space and time by the formation of shear bands at low homologous temperatures. Unveiling the mechanism of shear banding is hence key to developing a deeper understanding of plastic deformation in metallic glasses. We will compile recent progress in studying the dynamics of shear-band propagation from serrated flow curves. We will also take a perspective gleaned from stick-slip theory and show how the insights gained can be deployed to explain fundamental questions concerning the origin, mechanism, and characteristics of flow localization in metallic glasses.

In this article, scanning nonlinear dielectric microscopy (SNDM) with atomic resolution is reviewed. First, experimental results on the detection of ferroelectric domains are shown following a presentation about the theory and principle of SNDM. Next, a three-dimensional (3D) type of SNDM for measuring the 3D distribution of ferroelectric polarization and noncontact scanning nonlinear dielectric microscopy (NC-SNDM) are proposed. Using NC-SNDM under ultrahigh vacuum conditions, we clearly resolve the electric dipole moment distribution of Si atoms on a Si(111)7 × 7 surface. We also succeeded to resolve a fullerene (C60) molecule. Since the technique is applicable not only to semiconductors but also to both polar and non-polar dielectric materials, SrTiO3 and TiO2 surfaces were observed by NC-SNDM. Finally, we characterize an ultrahigh-density ferroelectric data storage system using SNDM as a pickup device and a congruent lithium tantalate single crystal as a ferroelectric recording medium.

The amorphous Si–B–C–N ceramics with a similar Si/C/N atomic ratio and various boron contents of 3.7 and 6.0 at.% B were synthesized and then isothermally annealed at temperatures ranging from 1550 to 1775 °C. The course of crystallization for the modifications of Si3N4 was examined by quantitative analysis of the corresponding x-ray diffraction patterns. Additionally, recent results of similar investigations on the ceramic with 8.3 at.% B were also considered. The kinetic analysis demonstrates that the controlling mechanisms of the Si3N4 crystallization, continuous nucleation and diffusion-controlled growth, are independent of the boron content. Nevertheless, the estimated activation energy of the crystallization significantly increases from 7.8 to 11.5 eV with the amount of boron ranging from 3.7 to 8.3 at.%. It is concluded that the role of boron in the crystallization kinetics is mainly due to the effect of boron on the nucleation process. Beside the kinetic analysis, the correlation between the boron content and the Si3N4 crystallite size has been discussed.

Device and sensor miniaturization has enabled extraordinary functionality and sensitivity enhancements over the last decades while considerably reducing fabrication costs and energy consumption. The traditional materials and process technologies used today will, however, ultimately run into fundamental limitations. Combining large-scale directed assembly methods with high-symmetry low-dimensional carbon nanomaterials is expected to contribute toward overcoming shortcomings of traditional process technologies and pave the way for commercially viable device nanofabrication. The purpose of this article is to review the guided dielectrophoretic integration of individual single-walled carbon nanotube (SWNT)- and graphene-based devices and sensors targeting continuous miniaturization. The review begins by introducing the electrokinetic framework of the dielectrophoretic deposition process, then discusses the importance of high-quality solutions, followed by the site- and type-selective integration of SWNTs and graphene with emphasis on experimental methods, and concludes with an overview of dielectrophoretically assembled devices and sensors to date. The field of dielectrophoretic device integration is filled with opportunities to research emerging materials, bottom–up integration processes, and promising applications. The ultimate goal is to fabricate ultra-small functional devices at high throughput and low costs, which require only minute operation power.

Expanded graphite/cobalt ferrite/polyaniline (EG/CF/PANI) ternary composites were obtained by a two-step process. The intercalation compound, CF embedded in EG, was synthesized by a coprecipitation method. PANI could then be coated on the surface of the EG/CF microparticles by in-situ polymerization to form ternary composites of EG/CF/PANI. The results indicate that the electrical and magnetic performance of EG/CF and EG/CF/PANI composites are related to their composition. The EG/CF composite with mass ratio of 1.0 has the maximal conductivity (833.33 S·cm−1) among the binary composites. Saturation magnetizations (Ms) of the EG/CF composite with mEG/mCF of 0.8 is the largest among EG/CF composites, the ternary composites of EG/CF/PANI were prepared from the EG/CF composite at this mass ratio. The electromagnetic wave absorbing property of all ternary composites excelled those of EG/CF composites, and the sample with 40 wt% of PANI has the best absorption properties in the range of 8–18 GHz frequency.

The poly (vinylidene difluoride) (PVDF) has been of great interest for energy conversion of microelectromechanical system devices. A semicrystalline polymer, the PVDF has five crystallographic forms, α, β, γ, δ, and ε. The latter four structures exhibit a permanent dipole moment. In this research, we investigated effects of microstructures of the PVDF on its piezoelectricity for energy harvesting. Using various experimental techniques, we observed the power density generated by a mechanical force that was correlated with the phase transformation between amorphous, α, β, and γ phases. The transformation was time-dependent in a nonlinear manner. Such transformation influences the energy transition and storage of small devices.

Shape memory alloys (SMA) undergo reversible martensitic transformation in response to changes in temperature or applied stress, resulting in the properties of superelasticity and shape memory. At present, there is high scientific and technological interest to develop these properties at small scales and apply SMA as sensors and actuators in microelectromechanical system technologies. To study the thermomechanical properties of SMA at micro and nanoscales, instrumented nanoindentation is widely used to conduct nanopillar compression tests. By using this technique, superelasticity and shape memory at the nanoscale have been demonstrated in micro and nanopillars of Cu–Al–Ni SMA. However, the martensitic transformation seems to exhibit different behavior at small scales, and a size effect on superelasticity has been recently reported. In this study, we provide an overview of the thermomechanical properties of Cu–Al–Ni SMA at the nanoscale, with special emphasis on size effects. Finally, these size effects are discussed in light of the microscopic mechanisms controlling the martensitic transformation at the nanoscale.

Single-crystal silicon test specimens, fabricated by lithography and deep reactive ion etching (DRIE), were used to measure microscale deformation and fracture properties. The mechanical properties of two specimen geometries, both in the form of a Greek letter Θ (theta), were measured using an instrumented indentation system. The DRIE process generated two different surface structures leading to two strength distributions that were specimen geometry independent: One distribution, centered about 2.1 GPa, was controlled by 35 nm surface roughness of scallops; the second distribution, centered about 1.4 GPa, was controlled by larger, 150 nm, pitting defects. Finite element analyses (FEA) converted measured loads into strengths; tensile elastic measurements validated the FEA. Fractographic observations verified failure locations. The theta specimen and testing protocols are shown to be extremely effective at testing statistically relevant (hundreds) numbers of samples to establish processing–structure–property relationships at ultrasmall scales and for determining design parameters for components of microelectromechanical systems.

Using scanning near-field lithography (SNP), it is possible to pattern molecules at surfaces with a resolution as good as 9 nm [M. Montague, R. E. Ducker, K. S. L. Chong, R. J. Manning, F. J. M. Rutten, M. C. Davies and G. J. Leggett, Langmuir23 (13), 7328–7337 (2007)]. However, in common with other scanning probe techniques, SNP has previously been considered a serial process, hindering its use in many applications. IBM’s “Millipede” addresses this problem by utilizing an array of local probes operating in parallel. Here, we describe the construction of two instruments (Snomipedes) that integrate near-field optical methods into the parallel probe paradigm and promise the integration of top–down and bottom–up fabrication methods over macroscopic areas. Both are capable of performing near-field lithography with 16 probes in parallel spanning approximately 2 mm. The instruments can work in both ambient and liquid environments, key to many applications in nanobiology. In both, separate control of writing is possible for each probe. We demonstrate the deprotection of self-assembled monolayers of alkylsilanes with photocleavable protecting groups and subsequent growth of nanostructured polymer brushes from these nanopatterned surfaces by atom-transfer radical polymerization.

Three-dimensional image-based modeling is used to investigate the correlations between crystallographic orientation and mechanical response in a body-centered cubic (BCC) β-titanium microstructure. Statistical significance is achieved by combining the simulation data of multiple image-based crystal plasticity models. Each individual model contains ∼100 grains and is subjected to uniaxial and biaxial tensile loading conditions. Although the use of smaller sub-volumes instead of a single large representative volume may preclude accurate prediction of the global stress–strain response of the material, it is demonstrated here that the microstructural and mechanical information at the local (grain) scale can be used to establish statistically significant microstructure–property correlations. It is shown that grains with <100> orientations aligned with the loading axis experienced much smaller effective stresses and strains than those with <110> and <111> orientations aligned with the loading axis under both types of loading conditions.

Substrate influence is a common problem when using instrumented indentation (also known as nano-indentation) to evaluate the elastic modulus of thin films. Many have proposed models to be able to extract the film modulus (Ef) from the measured substrate-affected modulus, assuming that the film thickness (t) and substrate modulus (Es) are known. Existing analytic models work well if the film is more compliant than the substrate. However, no analytic model accurately predicts response when the modulus of the film is more than double the modulus of the substrate. In this work, a new analytic model is proposed. This new model is shown by finite-element analysis to be able to accurately predict composite response over the domain 0.1 < Ef/Es < 10. Finally, the new model is used to analyze experimental data for compliant films on stiff substrates and stiff films on compliant substrates.

The effect of layer thickness on the hardness of nanometallic material composites with both coherent and incoherent interfaces was investigated using nanoindentation. Then, atomistic simulations were performed to identify the critical deformation mechanisms and explain the macroscopic behavior of the materials under investigation. Nanocomposites of different individual layer thicknesses, ranging from 1–30 nm, were manufactured and tested in nanoindentation. The findings were compared to the stress–strain curves obtained by atomistic simulations. The results reveal the role of the individual layer thickness as the thicker structures exhibit somehow different behavior than the thinner ones. This difference is attributed to the motion of the dislocations inside the layers. However, in all cases the hybrid structure was the strongest, implying that a particular improvement to the mechanical properties of the coherent nanocomposites can be achieved by adding a body-centered cubic layer on top of a face-centered cubic bilayer.

Miniaturization of components and devices calls for an increased effort on physically motivated continuum theories, which can predict size-dependent plasticity by accounting for length scales associated with the dislocation microstructure. An important recent development has been the formulation of a Continuum Dislocation Dynamics theory (CDD) that provides a kinematically consistent continuum description of the dynamics of curved dislocation systems [T. Hochrainer, et al., Philos. Mag.87, 1261 (2007)]. In this work, we present a brief overview of dislocation-based continuum plasticity models. We illustrate the implementation of CDD by a numerical example, bending of a thin film, and compare with results obtained by three-dimensional discrete dislocation dynamics (DDD) simulation.

Enthalpies of high-temperature phase transitions and fusion in lanthanum oxide (La2O3) were directly measured for the first time. Three samples were prepared by laser melting, sealed in tungsten crucibles, and heated in a differential thermal analyzer calibrated by melting Al2O3. Transformation enthalpy of La2O3 from A to H phase is 23 ± 5 kJ/mol at 2046 ± 5 °C and from H to X phase is 17 ± 5 kJ/mol at 2114 ± 5 °C. Lanthanum oxide melts at 2301 ± 10 °C, with enthalpy of fusion of 78 ± 10 kJ/mol.

Predicting the dislocation nucleation rate as a function of temperature and stress is crucial for understanding the plastic deformation of nanoscale crystalline materials. However, the limited time scale of molecular dynamics simulations makes it very difficult to predict the dislocation nucleation rate at experimentally relevant conditions. We recently develop an approach to predict the dislocation nucleation rate based on the Becker–Döring theory of nucleation and umbrella sampling simulations. The results reveal very large activation entropies, which originated from the anharmonic effects, that can alter the nucleation rate by many orders of magnitude. Here we discuss the thermodynamics and algorithms underlying these calculations in greater detail. In particular, we prove that the activation Helmholtz free energy equals the activation Gibbs free energy in the thermodynamic limit and explain the large difference in the activation entropies in the constant stress and constant strain ensembles. We also discuss the origin of the large activation entropies for dislocation nucleation, along with previous theoretical estimates of the activation entropy.