Reference Work Entry

Springer Handbook of Nanotechnology

pp 99-146

Nanowires

  • Mildred S. DresselhausAffiliated withDepartment of Electrical Engineering and Computer Science and Department of Physics, Massachusetts Institute of Technology
  • , Yu-Ming LinAffiliated withDepartment of Electrical Engineering and Computer Science, Massachusetts Institute of Technology
  • , Oded RabinAffiliated withDepartment of Chemistry, Massachusetts Institute of Technology
  • , Marcie R. BlackAffiliated withDepartment of Electrical Engineering and Computer Science, Massachusetts Institute of Technology
  • , Gene DresselhausAffiliated withFrancis Bitter Magnet Laboratory, Massachusetts Institute of Technology

Abstract

Nanowires are especially attractive for nanoscience studies as well as for nanotechnology applications. Nanowires, compared to other low dimensional systems, have two quantum quantum confinement confined directions while still leaving one unconfined direction for electrical conduction. This allows them to be used in applications which require electrical conduction, rather than tunneling transport. Because of their unique density of electronic states, nanowires in the limit of small diameters are expected to exhibit significantly different optical, electrical, and magnetic properties from their bulk 3-D crystalline counterparts. Increased surface area, very high density of electronic states and joint density of states near the energies of their van Hove singularities, enhanced exciton binding energy, diameter-dependent bandgap, and increased surface scattering for electrons and phonons are just some of the ways in which nanowires differ from their corresponding bulk materials. Yet the sizes of nanowires are typically large enough (> 1 nm in the quantum confined direction) to have local crystal structures closely related to their parent materials, thereby allowing theoretical predictions about their properties to be made on the basis of an extensive literature relevant to their bulk properties.

Not only do nanowires exhibit many properties that are similar to, and others that are distinctly different from those of their bulk counterparts, nanowires have the advantage from an applications standpoint in that some of the materials parameters critical for certain properties can be independently controlled in nanowires but not in their bulk counterparts. Certain properties can also be enhanced nonlinearly in small diameter nanowires by exploiting the singular aspects of the 1-D electronic density of states. Furthermore, nanowires have been shown to provide a promising framework for applying the “bottom-up” approach [4.1] for the design of nanostructures for nanoscience investigations and for potential nanotechnology applications. Driven by: (1) these new research and development opportunities, (2) the smaller and smaller length scales now being used in the semiconductor, opto-electronics, and magnetics industries, and (3) the dramatic development of the biotechnology industry where the action is also at the nanoscale, the nanowire research field has developed with exceptional speed in the last few years. A review of the current status of nanowire research is therefore of significant broad interest at the present time. This review aims to focus on nanowire properties that differ from those of their parent crystalline bulk materials, with an eye toward possible applications that might emerge from the unique properties of nanowires and from future discoveries in this field.