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

Lithium batteries, as a main power source or back-up power source for mobile communication devices, portable electronic devices and the like, have attracted much attention in the scientific and industrial fields due to their high electromotive force andhigh energy density. Tomeet the demand for batteries having higher energy density and improved cycle characteristics, in recent years, a great deal of attempt has been made to develop new electrode materials or design new structures of electrode materials. For anode materials, among them, some elementary substances such as silicon (Si), germanium (Ge), or tin (Sn) provide promising alternative to conventional carbonaceous anode active materials, because they are capable of alloying with more lithium and thus leading to the extreme high initial capacity density. For example, metallic tin has recently been widely concerned as one of the promising anode materials for lithium batteries due to the following reasons. Firstly, its theoretical specific capacity (Li4.4Sn, 992mAhg ) ismuchhigher than that of conventional graphite (LiC6, 372 mA h g ). Secondly, the tin anode has higher operating voltage than graphite, so it is less reactive and the safety of batteries during rapid charge/discharge cycle could be improved. Furthermore, a significant advantage of metallic tin over graphite is that it does not encounter solvent intercalationwhich causes irreversible charge losses at all. Unfortunately, the biggest challenge for employing metallic tin as applicable active anode materials is that it is suffering from huge volume variation during Liþ insertion/extraction cycle, which leads to pulverization of the electrode and very rapid capacity decay. Without appropriate structure design, the tin electrode typically fails after only a few discharge/charge cycles. It is therefore very desirable to design a new tinbased materials mainly composed of metallic tin with high specific capacity as well as good cycle performance. Some metal/oxides and carbon nanocomposites have been reported with high capacity and capacity retention when used as anodematerials, because the carbon shell has itself good electronic conductivity and prevents the aggregation of active materials, and especially thin carbon shell has good elasticity to effectively accommodate the strain of volume change during Liþ insertion/extraction. Very recently, tin-encapsulated spherical hollow carbon was synthesized by the pyrolysis of tin-containing organic precursors have exhibited higher capacity and better cycle performance than unencapsulated mixture materials, in which the content of tin active substance was only 24 wt%. Nanostructured tin dispersed in a carbonmatrix and carbon-encapsulated hollow tin nanopartides were also reported as superior anode materials. These studies showed that both coating tin nanomaterials with carbon layer and dispersing tin nanoparticles in carbon matrix are effective to improve their electrochemical properties in lithium ion batteries. It is obvious that thehigher content of and smaller size of tin, as well as the thinner carbon coating will greatly contribute to the further enhancement of material performance since the lithium storage density in tin ismuch higher than that in carbon. Meanwhile, this tin-based anode material has to be designed to own enough void volume to compensate the volume expansion during Liþ insertion, which is important to improve its cycle performance. In the presentwork,we therefore designed anewapproach to synthesize tin nanoparticles encapsulated elastic hollow carbon spheres (TNHCs) with uniform size, in which multiple tin nanoparticles with a diameter of less than 100 nm were encapsulated inone thin hollow carbon spherewith a thickness of only about 20 nm, thus leading to both the content of Sn up to over 70% by weight and the void volume in carbon shell as high as about 70–80%by volume. This void volume and the elasticity of thin carbon spherical shell efficiently accommodate the volume change of tin nanoparticles due to theLi-Sn alloying-dealloying reactions, and thus prevent the pulverization of electrode. As a result, this type of tin-based nanocomposites have very high specific capacity of >800 mA h g 1 in the initial 10 cycles, and >550mAh g 1 after the 100th cycle, as well as excellent cycling [*] Prof. L.-J. Wan, W.-M. Zhang, Dr. J.-S. Hu, Prof. Y.-G. Guo, S.-F. Zheng, L.-S. Zhong, Prof. W.-G. Song Beijing National Laboratory for Molecular Sciences Institute of Chemistry Chinese Academy of Sciences (CAS) Beijing 100080 (P.R. China) E-mail: wanlijun@iccas.ac.cn

Tin-Nanoparticles Encapsulated in Elastic Hollow Carbon Spheres for High-Performance Anode Material in Lithium-Ion Batteries†

SnO2: A comprehensive review on structures and gas sensors

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.

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

One-dimensional nanostructures of SnO2 with a ribbonlike morphology have been prepared in large scale via rapid oxidation of elemental tin at 1080 °C. The products were characterized with scanning electron microscopy, X-ray powder diffraction, transmission electron microscopy, Raman scattering, and photoluminescence spectroscopy. The as-synthesized SnO2 nanoribbons appeared to be single crystals and had preferred [110] and [203] growth directions. The lengths of the nanoribbons were up to several hundreds of micrometers, and the typical width and thickness were in the range of 30−150 nm and 10−30 nm, respectively. The strong photoluminescence of the nanoribbons in the visible region suggested possible applications in nanoscaled optoelectronic devices. A possible growth mechanism for the SnO2 nanoribbons was proposed.

Large scale rapid oxidation synthesis of sno2 nanoribbons

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

Large-Scale Rapid Oxidation Synthesis of SnO2 Nanoribbons.

Multi-tip cones induced by ion-bombardment

A method and an apparatus have been developed to fabricate large area uniform silicon cone arrays using different kinds of ion-beam sputtering methods. The apparatus includes silicon substrate as the silicon source, and metal foils are used as catalyst. Methods of surface modification of the as-synthesized silicon cones for field emission application have also been developed, including hydrofluoric acid etching, annealing and low work-function metal coating. Nano-structure modification based on silicon cones takes advantage of the fact that the cone tip consists of metal/metal siliside, which can be used as catalyst and template for nanowires growth. A method and an apparatus have been developed to grow silicon oxide/silicon nanowires on tips of the silicon cones.

Naigui Shang

Papers

Large scale rapid oxidation synthesis of sno2 nanoribbons

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

Large-Scale Rapid Oxidation Synthesis of SnO2 Nanoribbons.

Multi-tip cones induced by ion-bombardment

Large area silicon cone arrays fabrication and cone based nanostructure modification