Abstract Submitted to the NANOTUBE'02 Workshop:

Films of aligned multi-walled carbon nanotubes are grown by thermal chemical vapour deposition (CVD) on different substrates. The field emission measurements show that the films have excellent field emission properties with very high emission current densities and low turn-on and threshold fields. The results also show that the current density as a function of applied electric field (on multiple cycles) is reproducible up to a value around 1 mA/cm². Exceeding this value leads to light emission and irreversible changes occur in the nanotube film. Spectral measurements of this light shows a purely blackbody radiation effect with a temperature around 1550 K for the onset current density but temperatures over 2000 K are also seen for higher current densities. The correlation between the emission current and the light intensity provides convincing evidence for Joule heating as the source of the light emission. The onset of the light emission also occurs at approximately the same value as a noticeable change in the slope of the Fowler-Nordheim plot is seen. Scanning electron microscopy and Raman spectroscopy is used in order to determine the structure of the film before and after light emission has occurred.