Band model for electron emission from diamond and diamond-like carbon

The band diagram is constructed for diamond on metal and diamond-like carbon on metal emitters, from data for electron affinities, Schottky barrier heights or band offsets. For diamond, there is a large offset for the conduction band at the back-contact, causing this to be the dominant barrier for emission. Nitrogen and perhaps grain boundaries reduce this barrier by forming a depletion layer of ionised donors, which narrows the tunnelling distance. In DLC, there is little conduction band offset at the back-contact, and the dominant barrier is at the surface. Nitrogen now lowers the emission barrier by raising the bulk Fermi level and lowering the work function. Unresolved problems are also pointed out.