Three behavioral states observed in field emission from single-walled carbon nanotubes

We observe three distinct behavioral states in field emission from single-w alled carbon nanotubes between temperatures of 300 and 1800 K. At room temp erature, nanotubes emit through adsorbate states correlated to the presence of water. These states are removed above 900 K. After adsorbate removal, t he apparently clean nanotube state shows lower emission current and substan tially reduced emission noise. Current-temperature measurements identify a deviation from metallic tunneling behavior. Nanotube field emission undergo es a second, field-stabilized transition at high temperatures which reduces the current by as much as five orders of magnitude relative to the room te mperature current. This current decrease is 100% recoverable. In addition, the stable behavior of clean nanotube states breakdown at extremely high cu rrents and temperatures. Rings form around the field emission images, simil ar to those observed in metals at extreme current densities. Under these ex treme conditions, we also find evidence for the rearrangement of atoms on t he nanotube caps. (C) 1999 American Vacuum Society. [S0734-211X(99)07205-4] .