Ion-track nanotechnology at GSI

Nanowires and nanotubes are very interesting objects due to their novel properties and promising applications in various fields such as electronics, photonics, thermoelectrics, and sensorics. The properties of nanoscale materials, and thus their suitability and efficiency towards device implementation, depend strongly on the nanostructure’s geometrical and crystallographic characteristics. In this talk, the fabrication of nanowires and nanotubes in etched ion-track membranes will be presented. The potential of this technique to fabricate large arrays of micro- and nanowires rendering excellent control on wire size (diameter and length), morphology, crystalline structure, and composition will be discussed in detail. Ion-track technology makes use of high-energy heavy ions (MeV to GeV) to produce ion tracks in foils of insulating material (e.g. polymers, mica). The tracks consist of straight cylinders of damage with a width of a few nanometers that can be preferentially dissolved in an appropriate chemical solution, and subsequently enlarged to pores. Compared to other templates, ion-track membranes offer well-controlled pore diameter (between ~ 15 nm and few m), an extremely high length-to-diameter ratio (>103), as well as the possibility to adjust number density and relative orientation of the pores via the irradiation conditions. By electrochemical deposition, micro- and nanowires of different materials such as gold, copper, bismuth compounds, nickel, platinum, or zinc oxide are synthesized in the channels, mostly at ambient temperatures. Composition and crystallographic characteristics are successfully controlled by the deposition parameters. Finally, several examples will be presented to illustrate how size effects can tune the electrical, optical, or thermal properties of nanowires of various materials.