The present invention provides stretchable, and optionally printable, semiconductors and electronic circuits capable of providing good performance when stretched, compressed, flexed or otherwise deformed. Stretchable semiconductors and electronic circuits of the present invention preferred for some applications are flexible, in addition to being stretchable, and thus are capable of significant elongation, flexing, bending or other deformation along one or more axes. Further, stretchable semiconductors and electronic circuits of the present invention may be adapted to a wide range of device configurations to provide fully flexible electronic and optoelectronic devices.

http://science.sciencemag.org/content/sci/311/5758/208.full.pdf

Stretchable form of single crystal silicon for high performance electronics on rubber substrates

There are growing concerns over the environmental, climate, and health impacts caused by using non-renewable fossil fuels. The utilization of green energy, including solar and wind power, is believed to be one of the most promising alternatives to support more sustainable economic growth. In this regard, lithium-ion batteries (LIBs) can play a critically important role. To further increase the energy and power densities of LIBs, silicon anodes have been intensively explored due to their high capacity, low operation potential, environmental friendliness, and high abundance. The main challenges for the practical implementation of silicon anodes, however, are the huge volume variation during lithiation and delithiation processes and the unstable solid-electrolyte interphase (SEI) films. Recently, significant breakthroughs have been achieved utilizing advanced nanotechnologies in terms of increasing cycle life and enhancing charging rate performance due partially to the excellent mechanical properties of nanomaterials, high surface area, and fast lithium and electron transportation. Here, the most recent advance in the applications of 0D (nanoparticles), 1D (nanowires and nanotubes), and 2D (thin film) silicon nanomaterials in LIBs are summarized. The synthetic routes and electrochemical performance of these Si nanomaterials, and the underlying reaction mechanisms are systematically described.

Silicon-based Nanomaterials for Lithium-Ion Batteries - A Review

In recent years, near-nano (submicron) and nanostructured materials have attracted increasingly more attention from the materials community. Nanocrystalline materials are characterized by a microstructural length or grain size of up to about 100 nm. Materials having grain size of ∼0.1 to 0.3 μm are classified as submicron materials. Nanocrystalline materials exhibit various shapes or forms, and possess unique chemical, physical or mechanical properties. When the grain size is below a critical value (∼10–20 nm), more than 50 vol.% of atoms is associated with grain boundaries or interfacial boundaries. In this respect, dislocation pile-ups cannot form, and the Hall–Petch relationship for conventional coarse-grained materials is no longer valid. Therefore, grain boundaries play a major role in the deformation of nanocrystalline materials. Nanocrystalline materials exhibit creep and super plasticity at lower temperatures than conventional micro-grained counterparts. Similarly, plastic deformation of nanocrystalline coatings is considered to be associated with grain boundary sliding assisted by grain boundary diffusion or rotation. In this review paper, current developments in fabrication, microstructure, physical and mechanical properties of nanocrystalline materials and coatings will be addressed. Particular attention is paid to the properties of transition metal nitride nanocrystalline films formed by ion beam assisted deposition process.

/pdf/nanocrystalline-materials-and-coatings-1pj6y7x45z.pdf

Nanocrystalline materials and coatings

Silver has been prepared as triangular nanoplates with sharp corners and thin nanobelts by refluxing an aqueous dispersion of spherical colloids of silver with an average diameter of 3.5 nm. The spherical colloids of silver were, in turn, generated by reducing silver nitrate with sodium borohydride in the presence of poly(vinyl pyrrolidone) (PVP) and sodium citrate. Our studies indicate that the light present in an ordinary chemical laboratory was sufficiently strong to transform some spherical nanoparticles into small triangular nanoplates. Refluxing provided the driving force to facilitate the Ostwald ripening process−growth of these plate-like seeds at the expense of spherical nanoparticles. In addition, refluxing might also selectively disrupt the organic layers on the surfaces of the small triangular nanoplates, driving these plates to assemble into thin nanobelts due to the strong dipole−dipole interaction between adjacent plates. These nanostructures of silver with unique planar shapes might find u...

Transformation of Silver Nanospheres into Nanobelts and Triangular Nanoplates through a Thermal Process

This paper summarizes some of the essential aspects of silicon-nanowire growth and of their electrical properties. In the first part, a brief description of the different growth techniques is given, though the general focus of this work is on chemical vapor deposition of silicon nanowires. The advantages and disadvantages of the different catalyst materials for silicon-wire growth are discussed at length. Thereafter, in the second part, three thermodynamic aspects of silicon-wire growth via the vapor–liquid–solid mechanism are presented and discussed. These are the expansion of the base of epitaxially grown Si wires, a stability criterion regarding the surface tension of the catalyst droplet, and the consequences of the Gibbs–Thomson effect for the silicon wire growth velocity. The third part is dedicated to the electrical properties of silicon nanowires. First, different silicon nanowire doping techniques are discussed. Attention is then focused on the diameter dependence of dopant ionization and the influence of interface trap states on the charge carrier density in silicon nanowires. It is concluded by a section on charge carrier mobility and mobility measurements.

/pdf/silicon-nanowires-a-review-on-aspects-of-their-growth-and-20jrcf5p99.pdf

Silicon Nanowires: A Review on Aspects of their Growth and their Electrical Properties

Silicon is one of the most important electronic materials. Its nanoscale forms, such as nanocrystals, porous silicon, quantum wells, and nanowires, have stimulated great interest among scientists because of their peculiar physical properties, such as light emission, field emission, and quantum confinement effects. The progress made in the synthesis of silicon nanostructures and nanowires in recent years has attracted considerable attention. Today, large quantities of silicon nanowires can be produced by the laser ablation of metalor SiO2-containing silicon targets, [8] and a few properties, such as electric and thermal conductivity and optical properties, have also been studied. However, the experimental characterization and application of silicon nanowires, for example, the measurement of the elastic properties, the realization of efficient field emission of nanoscale silicon, and the fabrication of nanometer field effect transistors and planar displays, have been hampered so far because of the difficulty in growing oriented silicon nanowires. As a result, the production of highly oriented and very long silicon nanowires is a very important and challenging issue. In this communication, we report the successful synthesis of highly oriented, largescale, and very long silicon nanowires on flat silicon substrates by thermal evaporation of silicon monoxide (SiO). The growth mechanism and optical properties of the oriented silicon nanowires are also discussed. To the best of our knowledge, the synthesis of oriented silicon nanowires has not yet been reported. The equipment used for the present work is similar to that described previously. An alumina tube was mounted inside a tube furnace. The SiO powders (Gooodfellow, 99.95 %) were placed near the middle of the high-temperature zone of the furnace. The polished silicon (100) substrates about 5 mm in width and 50 mm in length were ultrasonically cleaned in acetone, ethanol, and deionized water for 20 min each, dipped in 20 % HF for 20 min, and finally rinsed in deionized water for 20 min before they were placed abreast at one end of the alumina tube. The tube had previously been evacuated to a base pressure of 10 torr by a mechanical pump before the starting materials were heated. The carrier gas of argon mixed with 5 % H2 admitted at the other end of the alumina tube flowed at 50 sccm (standard cubic centimeters per minute) at 400 torr. The temperature of the furnace was increased to 1300 C at 6 C/min and kept at this temperature for 7 h. The temperature of the silicon substrate surface where the oriented silicon nanowires grew was found to be approximately 930 C, which differed from that at the center due to the temperature gradient within the tube. The product was first directly examined by scanning electron microscopy (SEM, Philips XL 30 FEG). Microstructural characterization was carried out in a conventional Philips CM 20 transmission electron microscope (TEM) at 200 kV. The high-resolution transmission electron microscopy (HRTEM) study was performed in a Philips CM200 FEG transmission electron microscope, operated at 200 kV accelerating voltage at room temperature. The chemical compositions of the samples were determined by an energy dispersive X-ray (EDX) spectrometer attached to both the SEM and HRTEM instruments. Raman scattering spectra were measured with a Renishaw micro-Raman spectrometer at room temperature. Excitation was by means of the 514 nm line of an Ar laser, and the Raman signals were measured in a backscattering geometry with a spectral resolution of 1.0 cm. The deposited silicon nanowire product is light yellow in color. SEM images at different magnifications of a typical sample in Figures 1a, 1b, 1c, and 1d clearly show the large area of highly oriented nanowires on the surface of the silicon substrate. The low magnification SEM image (Fig. 1a) shows that the area of highly oriented silicon nanowires is about 2 mm ́ 3 mm and the lengths of individual nanowires are up to 1.5±2 mm. The thickness of the oriented nanowire product was about 10 lm, as estimated from the cross-sectional image (Fig. 1d) of the sample prepared by focused ion beam cutting. The highly oriented array of Si nanowires can also be observed from the cross-sectional image. The EDX results show that the nanowires are composed of silicon and oxygen. No metal was found in the sample. Such results are consistent with our previous theory that silicon nanowire growth is enhanced by silicon oxide instead of a metal particle catalyst. Because of local charging effects, the diameters observed from SEM images appear larger than the actual wire diameters. More information about the morphology of silicon nanowires is given by the following TEM characterization Small pieces of oriented silicon nanowire samples were peeled off from a silicon substrate and mounted on a folding grid for TEM and HRTEM observations. Figure 2 shows the typical morphology of silicon nanowires. As reported previously, these nanowires show a better orientation than those synthesized by laser ablation. Silicon nanowires as observed by TEM are quite clean, with very few particles attached to their surfaces, and are relatively homogeneous. Analysis of a number of nanowires shows that the diameters of these silicon nanowires vary from 18 to 46 nm, and the mean value is about 30 nm. The selected-area electron dif-

/pdf/synthesis-of-large-areas-of-highly-oriented-very-long-2c1fjamrcx.pdf

Synthesis of Large Areas of Highly Oriented, Very Long Silicon Nanowires

Silicon carbide (SiC) nanowires were synthesized at 900°C by the laser ablation technique. The growth morphology, microstructure, and defects in SiC nanowires were characterized by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The Raman scattering study indicated that the Raman peaks corresponding to the TO and LO phonon modes of the SiC nanowires had larger red shifts compared to those of bulk SiC material. The red shift, broadening peak, and the asymmetry of the Raman peak could be explained by the size confinement effect in the radial and growth directions. The growth mechanism of SiC nano-wires was discussed based on the vapor–liquid–solid reaction.

Laser Ablation Synthesis and Optical Characterization of Silicon Carbide Nanowires

Free-standing single crystal silicon nanoribbons.

http://lbmd.coe.pku.edu.cn/PDF/2000CPL-(GaN).pdf

Hongying Peng

Papers

Synthesis of Large Areas of Highly Oriented, Very Long Silicon Nanowires

Laser Ablation Synthesis and Optical Characterization of Silicon Carbide Nanowires

Free-standing single crystal silicon nanoribbons.

Bulk-quantity GaN nanowires synthesized from hot filament chemical vapor deposition

Thin β-SiC nanorods and their field emission properties