The effects of gas adsorbates on the field emission of carbon nanotube arrays have been observed and studied experimentally (Lim et al. Adv. Mat. 2001). In order to gain an understanding of these effects at the molecular level, we performed a density functional theory study on the adsorption of N2, O2, H2, and H2O at capped and open-end tips of single wall carbon nanotubes. The current suppression at high voltage observed in many I-V experiments, which is causing the emission to deviate from Fowler-Nordheim curve, will be discussed in light of our results.
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