August 22, 2011 — Nanowires tend to grow in unruly tangles, but a new structured substrate from the Weizmann Institute of Science is producing long, straight, aligned semiconductor nanowires for semiconductors like LEDs and transistors, photovoltaics, lasers, storage media, and other applications.
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| Figure 1. Nanowires growing along nanogrooves. |
Prof. Ernesto Joselevich, Ph.D., of the Weizmann Institute’s Chemistry Faculty, Ph.D. student David Tsivion and postdoctoral fellow Mark Schvartzman of the Materials and Interfaces Department grew nanowires made of gallium nitride (GaN), using a sapphire base. Instead of growing nanowires vertically (which become tangled when manipulated into arrays), the researchers cut the sapphire along different planes of the crystal, creating a nanoscale step pattern with accordion-like, V-shaped grooves in which nanowires grew horizontally. The team therefore combined synthesis and assembly of the nanowires.
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| Figure 2.Top view of the nanowires, scanning electron microscopy (SEM). |
The surface steps and grooves guide mm-long nanowire arrays to grow along their edges and within the depressions of the grooves. Optical and electronic properties were as good or better than those of vertically grown nanowires, without the defects that Joselevich expected horizontal growth to induce. The team credits its vertical-growth process, tuned to produce horizontal growth, for this high quality, though more research is needed to better understand what’s happening.
The results are published in Science at http://www.sciencemag.org/content/333/6045/1003.short
Learn more at the Weizmann Institute of Science, http://wis-wander.weizmann.ac.il/ (English)