Low threshold field emission from amorphous carbon films grown by electrochemical deposition

Electrochemical deposition of amorphous carbon (a-C) film is performed by applying a bias voltage to substrate immersed in methanol. Both scanning electron microscopy and Raman results indicate that smooth and homogeneous a-C films are grown. on specific substrate materials such as Si, Ti, and Al. Field emission measurements demonstrate excellent emission properties such as threshold fields lower than 5 V/mu m. Field enhancement factors are estimated to be 1300-1500; these are attributed to local field enhancements around sp(2) carbon clusters that are embedded in the a-C films. Emission properties of a-C films grown on Si exhibit a current saturation under higher applied fields. These saturation behaviors are explained by an effect of a potential barrier formed at the interface between a-C films and substrates. Since the interface barrier is reduced by formation of the TiC interfacial layer, an approach to utilize carbide formation at the interface is verified as useful to improve the emission properties of a-C films.