Inside Front Cover: Self‐Assembly of SiO2 Nanowires and Si Microwires into Hierarchical Heterostructures on a Large Scale (Adv. Mater. 8/2005)

The inside cover shows a scanning electron micrograph of a novel hierarchical heterostructures, as reported by Hu and co‐workers on p. 971. The heterostructures are formed from Si core microwires covered by dense, aligned SiO₂ nanowires, thus forming multiple junctions to the cores. The inset shows a schematic of the Sn‐catalyzed vapor–liquid–solid growth mechanism. These materials are envisaged to become important for optical fibers, low‐dimensional waveguides, scanning near‐field optical microscopes and high‐bandwidth optical signal processing devices.     

Supercritical Fluid–Liquid–Solid (SFLS) Synthesis of Si and Ge Nanowires Seeded by Colloidal Metal Nanocrystals

Semiconductor nanowires, 5 to 20 nm in diameter and micrometers in length, appear to be promising candidates for a variety of new technologies, including computing, memory, and sensor applications. Suitable for these applications, silicon (Si) and germanium (Ge) nanowires ranging from 4 to 30 nm in diameter and micrometers in length can be produced in high temperature supercritical fluids by thermally degrading organosilane or organogermane precursors in the presence of organic‐monolayer‐protected gold nanocrystals. Although gas phase vapor–liquid–solid (VLS) methods can be used to produce a variety of different nanowire materials, high temperature supercritical fluids provide wire size control through nanocrystal size selection prior to synthesis, and high product yields due to the high precursor solubility.     

Cover Picture: Epitaxial Growth of Indium Arsenide Nanowires on Silicon Using Nucleation Templates Formed by Self‐Assembled Organic Coatings (Adv. Mater. 14/2007)

On p. 1801, Lars Samuelson and co‐workers report on InAs nanowires that are grown directly on Si substrates by employing self‐assembled organic coatings to create an oxide template which guides nanowire nucleation. The nanowires extend vertically from the Si(111) substrate (foreground). No metal catalysts are used, and the InAs crystal extends to the nanowire tip as shown in the atomically resolved transmission electron microscopy image (dome background). The reported method constitutes a promising approach to the integration of new components into existing Si technology.