Effect of adsorbates on field emission from flame-synthesized carbon nanotubes.

We report the influence of adsorbates on field emission from flame-synthesized patterned carbon nanotubes (CNTs) by varying current-voltage sweep operational modes (continuous and pulsed) and vacuum pressure. Based on the gas adsorption and desorption effect, three distinguishable emission regimes--intrinsic adsorption, field-induced adsorption enhanced and current-induced desorption regimes--were proposed to interpret the nonlinearity of Fowler-Nordheim plots. The field-emission current versus applied voltage curves exhibited distinctive vacuum-pressure- and sweep-speed-dependent hysteresis upon a loop of anode voltage. This hysteresis was attributed to the absorption-desorption of adsorbates due to the large surface defects of the flame-synthesized CNTs. Such flame-synthesized CNTs with distinctive gas-absorption ability may have potential application in gas-sensing field-emission devices. [ABSTRACT FROM AUTHOR]