Understanding tube-like electron emission from nanographite clustered films

Diamond-like carbon and amorphous carbon films are known for their high smoothness root mean square values which can be as low as 0.1 nm. When used in field emission, physical aspects of enhancement are often disregarded for such flat film emitters. However, it is proven that these films may not be as flat as they appear to be. We present an experimental validation that shows a tube or needle-like emission mechanism for nanosized graphite clusters embedded in an amorphous carbon matrix. Films were deposited with in situ heating at 100, 400 and 700 degrees C and enhancement factors were seen to increase twofold as temperature was increased. By varying the anode-cathode distances, the films exhibited a distance dependency that is only observed for tubes and needle structures. This suggests that flat films can exhibit an emission mechanism akin to carbon nanotubes, thus confirming the presence of conductive channels within the films for nanoclustered amorphous carbon films. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3610514]