Electrical Properties of Nanowires and Nanofibers

Abstract

This chapter focuses on the electrical properties of nanowires, nanofibers, and nanotubes made from a variety of materials. First a short review of their morphologies and composition is presented, emphasizing the wide variety of elements and compounds able to be fabricated as long-aspect ratio nanomaterials. Research of nanowires and nanofibers indicates that depending on their composition and dimensions, they can either be insulating, semiconducting, metallic, or superconducting. Several interesting effects appearing at nanoscale are discussed, among which proximity-induced superconductivity in wires made of nonsuperconducting materials due to superconducting electrodes, a switch in electrical behavior from metallic to semiconducting with chirality of carbon nanotubes, and metallicity of one-dimensional materials confined inside nanotubes that are semiconducting in bulk. Due to their small dimensions, nanowires and nanofibers present new challenges regarding their electrical properties. Small amounts of bending strains induce a semiconductor-metal transition in small diameter semiconducting nanowires. Their encapsulation in stronger nanotubes offers advantages, such as increase their mechanical strength and protect them from interacting with the atmosphere. Some materials fabricated as nanowires, while nonsuperconducting in bulk form, show superconductivity only on the nanowire surface. Last but not least, the toxic effects on humans due to handling nanowires and nanofibers are emphasized.