Effect of nanostructure and back contact material on the field emission properties of carbon films

The emission properties of carbon films grown by pulsed laser ablation are investigated in relation to their nanostructure, which changes from amorphous to nanostructured carbon, according to the substrate temperature. In addition to an increasing number and size of six-member carbon rings, Raman scattering measurements reveal light polarisation sensitivity, reflecting a temperature-induced orientation of graphene domains. Such characteristics largely affect the electron emission properties, resulting in a close relation among threshold field values, graphene domain size and probably their average orientation. These results are interpreted suggesting that hot electron generation and transport through graphene domains is one of the main mechanisms enhancing the electron emission probability. A lowering of the threshold field strength is also observed when carbon films are deposited on titanium substrate in respect to the silicon one.