Gehui Wen

Ultra-small single-walled carbon nanotubes and their superconductivity properties

Abstract Ultra-small single-walled carbon nanotubes (SWNTs) are successfully fabricated in the channels of zeolite AlPO4-5 (AFI) single crystals by pyrolysis of tripropylamine molecules in the channels. These nanotubes have been observed directly by transmission electron microscopy, as well as by diffuse X-ray scattering and micro-Raman measurements of the nanotube breathing mode. The data consistently indicate a nanotube diameter of as small as 0.4xa0nm, probably at or close to the theoretical limit. These mono-sized small nanotubes perhaps constitute the best example of one-dimensional (1-D) quantum wires. They show novel electronic properties. Investigation of the magnetic and transport properties of single-walled small diameter carbon nanotubes embedded in a zeolite matrix revealed that at temperatures below 20xa0K, 0.4xa0nm tubes exhibit superconducting behavior manifest as an anisotropic Meissner effect, with a superconducting gap and fluctuation super-current. The measured superconducting characteristics display smooth temperature variations owing to 1-D fluctuations, with a mean field superconducting transition temperature of 15xa0K.

Fabrication of mesoscopic devices using atomic force macroscopic electric field induced oxidation

We demonstrate the fabrication of mesoscopic devices on aluminum, titanium, and silicon-on-insulator thin films by using atomic force microscopic electric field induced oxidation together with selective wet etching. The fabricated device structure is a percolating network consisting of conducting dots (50–100 nm in diameter) randomly distributed within an area of 1×1 μm2. Details on how to fabricate the network structure and the making of electrical contacts to the device will be focused upon. Good agreement between results from transport measurement of an aluminum test sample we made and data from the literature warrants reliability of our sample fabrication technique.