Nonlithographic nano-wire arrays: fabrication, physics, and device applications

A novel system of nanostructures is described consisting of nonlithographically produced arrays of nano-wires directly electrodeposited into porous anodic aluminum oxide templates. Using this method regular and uniform arrays of metal or semiconductor nano-wires or nano-dots can be created with diameters ranging from ~5 nm to several hundred nanometers and with areal pore densities in the ~10⁹-10¹¹ cm^-2 range. We report on the present state of their fabrication, properties, and prospective device applications. Results of X-ray diffraction, Raman and magnetic measurements on metal (Ni, Fe) and semiconductor (CdS, CdSe, CdS_x Se_1-x, Cd_xZn_1-xS and GaAs) wires are presented. The I-V characteristics of two terminal devices made from the nano-arrays are found to exhibit room temperature periodic conductance oscillations and Coulomb-blockade like current staircases. These observations are likely associated with the ultra-small tunnel junctions that are formed naturally in the arrays. Single-electron tunneling (SET) In the presence of interwire coupling in these arrays is shown to lead to the spontaneous electrostatic polarization of the wires. Possible device applications such as magnetic memory or sensors, electroluminescent flat-panel displays, and nanoelectronic and single-electronic devices are also discussed