Anisotropic properties of carbonaceous material produced in arc discharge

A helium-pressure influence on the structure and properties of carbonaceous material from the inner part of a deposit forming in an arc discharge has been studied. At the helium pressure of about 150 Torr and higher, the material was found to have a layered texture, which is perpendicular to the deposit growth axis. Electron microscopy measurements showed that a sample produced in He gas of 800 Torr consists of ∼80% carbon nanotubes having predominant orientation in the layers. Electric conductivity along and perpendicular to the samples’ surface have been measured from 4.2 to 500 K. The samples synthesised at higher helium pressures have significant anisotropy of conductivity, increasing with the carbon nanotubes content rise. X-ray fluorescence spectra represented the angle dependence that is caused by the anisotropy of chemical bonding in the carbon nanotubes. The valence π- and σ-bands for the carbonaceous material were separated. Received: 26 November 1999 / Accepted: 20 April 2000 / Published online: 10 January 2001