Effects of adsorbates on field emission reproducibility of sulfur-incorporated nanocomposite carbon films

The effects of adsorbates on field emission reproducibility from sulfur-incorporated nanocomposite carbon films grown by hot filament chemical vapor deposition were studied. Adsorption was induced on the films by liquid treatment at standard conditions using polar (1-butanol), moderately polar (ethyl acetate), and nonpolar (hexane) liquids. Adsorbates caused an increase in the turn-on field that was found to depend on the polarity of the liquid used: the larger (smaller) the polarity, the smaller (larger) the increase in turn-on field. The analysis of the data indicates that the increase in turn-on field is due to an increase in work function caused by adsorbates. Moreover, the hysteresis behavior, present in the field emission measurements, changes from clockwise to counterclockwise due to the adsorbates. The results are discussed in terms of the affinity between the adsorbates and the films’ surface and the adsorption-desorption process occurring on the films’ surface during emission.