Electrical properties of individual Single-Walled Carbon Nanotube/rope in the configurations of 2-probe resistance, field
effect transistor (FET), and thermopower have been measured. It is shown that oxygen adsorption in SWNTs is indeed a
physisorption process. The p-type behavior of SWNTs in the ambient is believed to be due to the Fermi level pinning at
impurity states of O<sup>2-</sup> near the top of the valence band of the tube. Chemisorption processes involving ammonia and
nitrous oxide have been explored by studying FET properties. The thermoelectric power of individual ropes of SWNTs
is measured and related to the FET properties.