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Stretchable electronics, i.e. elastic electronics that can be bent and stretched, is a new, emerging class of electronics, based on building electronic circuits or devices on stretchable substrates. The potential applications range from fully conformable, stretchable, skin sensors for robotic devices, wearable electronic devices, to flesh-like biodevices. One of the challenges in the development of stretchable electronics is to retain full functionality under high external strains in stretching. In this paper, we review a few approaches recently developed for stretchable electronics and highlight recent research efforts on multi-directional writing for stretchable, three-dimensional structures.

We report variations in the currents of CdZnTe semiconductor crystals during exposure to a series of light emitting diodes of various wavelengths ranging from 470 to 950 nm. The changes in the steady-state current of one CdZnTe crystal with and without illumination along with the time dependence of the illumination effects are discussed. Analysis of the de-trapping and transient bulk currents during and after optical excitation yield insight into the behaviour of charge traps within the crystal. Similar behaviour is observed for illumination of a second CdZnTe crystal suggesting that the overall illumination effects are not crystal dependent.

A new cost-effective and efficient approach is proposed for texturing the crystalline silicon using the gas-lift effect (GLE). The advantages of this approach over the conventional ones are that significantly lower amounts of IPA is used and much shorter etching time is required to achieve the same reflectivity. GLE is generated by taking advantage of the hydrogen bubbles evolved between the silicon wafer being etched and a glass plate, placed in parallel, creating a gap of 1–2 mm. This effect then acts as a pumping mechanism detaching more bubbles from the silicon surface, accelerating them to the top and out of the system, as quickly as they are generated. Experiments were carried out with various combinations of TMAH/IPA concentrations for two different GLE conditions to analyse and determine their influence on etching time, etching rate, surface morphology and reflectivity of the textured silicon surface. The use of this new approach in surface texturing, allowed the reduction of the required IPA by 50% and etching time by more than 60% to achieve the same reflectivity. This can ultimately lead to a significant reduction in cost by increasing the efficiency of the texturing process. A combination of 3.5% IPA and 2 mm GLE resulted in a textured silicon surface having a low specular solar-weighted reflectivity of 0.15%.

Femtosecond laser–metal interaction in air and the resultant early plasma evolution are investigated by a two-dimensional comprehensive hydrodynamic model in this paper. The model comprises a two-temperature model and a hydrodynamic model supplemented with a quotidian equation of state model, considering the relevant multiphysical phenomena during the laser–metal interaction. The experimental measurements for plasma expansion were carried out to validate the simulation results, using a shadowgraph technique and direct fluorescence measurement. The evolution of both the early plasma and plume plasma is investigated by the model. The early plasma is proved to be generated by electron emission and ambient gas ionization and splits into several portions during its expansion due to different mechanisms. The plume plasma comes from the target material ejection. The photoelectric emission is revealed to be the dominant electron emission mechanism at high laser intensities, while thermal emission is more important at low laser intensities. The electron emission process and early stage plasma are critical to ultrashort laser–metal interaction, especially at high laser intensities. Without considering this, the electron temperature can be overestimated by as much as 70%.

Optically active Au : TiO₂ nanocomposite thin films with an amount of gold of about 15 at% were prepared by dc reactive magnetron sputtering. After the deposition, the samples were annealed in vacuum at different constant temperatures between 200 and 800 °C. Depending on the annealing temperature, considerable changes have been found in the films' crystalline structure and for the number, the shape and the dimensions of the Au clusters. Modulated IR Radiometry (MIRR), a non-contact, non-destructive modulation-frequency-dependent photothermal measurement technique, was used for the characterization of the thermo-optical depth profiles of the as-deposited and annealed samples. Based on the results of MIRR, it was possible to establish correlations of the measured thermo-optical depth profiles with various effects: the heat treatment induced progress of crystallization of the TiO₂ matrix, the evolution of Au nanoparticles and strong subsurface heat sources related to the surface plasmon resonance (SPR) effect. For the annealing temperature of 800 °C, a diffusion and accumulation of gold just at the surface was found, which contributes to limit the subsurface heat sources and the SPR effect.

We investigate the connectivity between aeration voids (radius 200–300 µm) and pores (radius 20 µm) in aerated gypsum plaster using two-dimensional (2D) nuclear magnetic resonance T₂–T₂ relaxation time exchange experiments. These measurements provide an estimate of diffusive exchange rates for water molecules moving between environments differentiated by relaxation time. Aerated gypsum is a lightweight material manufactured by the inclusion of voids to reduce the bulk density. Such materials exhibit a multi-modal distribution of pore and void sizes and are associated with novel water imbibition processes. Here, we use T₂–T₂ exchange experiments to characterize the extent of fluid communication between the voids and pores to better understand the structure–transport relationships in these systems. In turn, this will aid the design of gypsum plasters with improved physical and mechanical properties. Utilizing an analytical model based on diffusion-driven exchange, we extract exchange times and hence diffusive length-scales, which are equivalent to the pore diameter. Overall, we conclude that the voids and pores are well connected. This confirms our previous hypothesis that water uptake occurs via capillary-driven imbibition through a continuum of voids and pores in aerated gypsum.

The influence of SiO₂ and Si₃N₄ dielectric matrices on the structural, phonon, luminescence and thermal properties of Ge quantum dots (QDs) has been experimentally investigated. Compared with the case of QDs in SiO₂ layers, Si₃N₄ matrix imposes large interfacial surface energy on QDs and enhances their Ostwald ripening rate, appearing to be conducive for an improvement in crystallinity and a morphology change to a more perfectly spherical shape of Ge QDs. Quantum confinement induced electronic structure modulation for Ge QDs is observed to be strongly influenced not only by the QD size but also by the embedded matrix. Both matrix and surface effects offer additional mechanisms to QD itself for controlling the optical and thermal properties of the QDs.

The mechanism of light leakage in the dark state of a blue phase liquid crystal display cell which has protruded electrodes was investigated. We have performed a hybrid numerical simulation by combining the geometrical optics with the extended Jones matrix method. The light leakage in the cell was caused by changes in the polarization state which has been explained by the asymmetric amplitude change of transverse electric and transverse magnetic fields at the oblique interface and the change in an effective angle between crossed polarizers by the light path refraction. Based on our analysis, light leakage can be suppressed by the matching of the refractive indices of adjacent materials to the interface of the protruded electrodes whose surfaces are not parallel to the substrate.

The ternary ceramics of Pb(Yb_1/2Nb_1/2)O₃–Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ (PYMNT) solid solution system is prepared by a two-step synthetic process. Its structure and electrical properties are studied. All the obtained ceramics have pure perovskite structure. It is noted that the morphotropic phase boundary (MPB) of the PYMNT ternary system is not a linear region which is between the MPB compositions of PMNT and PYNT binary systems. The Curie temperature T_C of the ternary system varies in the range 165–370 °C and the piezoelectric coefficient d₃₃ varies in the range 335–505 pC N⁻¹. With increasing PYNT content, the dielectric constants ε' decrease and the coercive field E_c increases. Therefore, the electric properties and T_C can be adjusted by selection of composition. The results show that the PYMNT ceramic exhibits higher Curie temperature, larger coercive field and good piezoelectric properties, making it a promising material for high-power electromechanical transducers that can operate in a large temperature range.

We report on experiments conducted on single-walled carbon nanotube bundles aligned in chains and connected through a natural contact barrier. The dependence upon the temperature of the transport properties is investigated for samples having different characteristics. Starting from two bundles separated by one barrier deposited over four-contact probes, we extend the study of the transport properties to samples formed by chains of several bundles. The systematic analysis of the properties of these aggregates shows the existence of two conduction regimes in the barrier. We show that an electrical circuit taking into account serial and parallel combinations of voltages generated at the junctions between bundles can model the samples consistently.

Atomic force microscopy, wavelength-dispersive x-ray spectroscopy and photoemission electron microscopy were used to study the contact formation of Au/V/Al/V-based contacts on n-type GaN. After a rapid thermal annealing contact formation step, we find that the surface is composed of dendritic structures. The dendrites are Au-rich, while the voids between the branches of the dendrites are V-rich, and cracks in the voids are Ga-rich. A detailed model of the chemical structure and morphology of V-based contacts on n-GaN is given and discussed in view of the ohmic-like behaviour of such contacts.