Synopsis: Self-Elongating Nanowires

A new self-assembly process creates nanowires of germanium without the metal catalyst required in earlier experiments.
Synopsis figure
J. J. Zhang et al., Phys. Rev. Lett. (2012)

Traditional “top-down” methods for fabricating nanodevices are hampered by defects and other irregularities. Growing interest has therefore centered on bottom-up strategies that involve the self-assembly of individual components. As part of this trend, scientists have developed a novel method for producing germanium nanowires that, unlike previous efforts, can be grown directly on a microchip during fabrication without the need of any metal catalyst to drive the self-assembly.

Bottom-up fabrication is highly precise and reproducible, since the desired component is essentially built atom by atom. Semiconductor nanowires, for example, grow incrementally, like tiny plant shoots, with the help of metal nanostructures that concentrate the semiconductor material and then extrude it in a single direction. One drawback of this method is that the metal catalyst can contaminate the wire. Another is that integration of such vertically grown wires into silicon technology is extremely challenging.

To avoid this problem, Jianjun Zhang of the Leibniz Institute for Solid State and Materials Research in Dresden, Germany, and his colleagues developed a catalyst-free way to make nanowires on a flat surface. Using molecular beam epitaxy, they deposited a thin layer of germanium on a silicon substrate. They then annealed their samples at 560C. The germanium first collected into well-known tent-shaped islands called “hut clusters.” But after a few hours, these islands stretched out to a few microns in length, while maintaining a height of roughly three unit cells (or about 2 nanometers). Theoretical modeling showed that the wires grew because the tent shape reduces the surface energy of the germanium layer. The small and uniform cross section of the nanowires could make them ideal for certain devices, such as those that control the spin of the charge carriers. – Michael Schirber


More Announcements »

Subject Areas

NanophysicsMaterials Science

Previous Synopsis

Next Synopsis

Related Articles

Focus: Complex Crystals Form from Heterogeneous Particles
Materials Science

Focus: Complex Crystals Form from Heterogeneous Particles

A suspension containing particles with wide-ranging diameters can crystallize into multiple ordered structures. Read More »

Synopsis: Glassy Fingerprints
Condensed Matter Physics

Synopsis: Glassy Fingerprints

The local structure of glasses and other disordered materials could be extracted from diffraction patterns, according to a proposal for a new technique. Read More »

Synopsis: Electron–Phonon Affair Comes to Light
Condensed Matter Physics

Synopsis: Electron–Phonon Affair Comes to Light

Photoelectron spectroscopy reveals the details of the interaction between electronic and vibrational excitations in a molecular material. Read More »

More Articles