Nanowire
A nanowire is a fine, elongated piece of metal, semi-metal or compound semiconductor having a diameter in the range up to 100 nanometers ( 0.1 micrometers = 0.0001 mm).
A frequently used in research methods for the preparation of the embedded nanowires, or free, the electrochemical deposition of the desired metal into suitable nano- pores and then leaching. Suitable, for example, the pores of alumina, which can be dissolved with a strong base or with hydrofluoric acid.
Another frequently used, method is the direct growth in a vapor-liquid -solid process. This is both for growth on a substrate, as well as for preparing non- nanowires, which are removed with the gas flow through the reactor, can be used. The diameter of the nanowires thus produced depends on the droplet size of the catalyst used. The production of metal droplets in the nanometer range is difficult, because they are not thermodynamically stable.
Conductive metallic carbon nanotubes can be also referred to as nano- wire in the sense of an electrical conductor.
In the semiconductor technology, nanowires are fabricated using lithographic processes that are particularly complex, in this case, since the desired structures are smaller than the wavelength of visible light. One must, therefore, apply special procedures and work with short-wavelength light such as UV light (eg laser light with 193 nm wavelength). Meanwhile chips can be made with a wire width of 32 nm ( as of 2011).
New research also deal with the production of nanowires based on DNA. In this case, DNA strands are metallized to increase the conductivity. During metallization with, for example, silver, there is at the same time a cross-linking of adjacent strands. In a second metallization gold can be deposited from a solution of the silver particles. The duration of the deposition of gold, the diameter of the nanowires can be varied. With the new method, we obtain micrometer- long, electrically contactable nanowires that have the potential for the production of miniaturized circuits.