Field emission of nitrogenated amorphous carbon films Original Research Article

Field emitter films based on nitrogenated amorphous carbon (a-C:N) were deposited on different chromium patterns on glass by sputtering of graphite employing an electron cyclotron resonance plasma as argon and nitrogen ion source. The a-C:N films contain between 0.6 and 21 at.% nitrogen. All films have a low resistivity (<0.1 Ωcm) and a microhardness of about 15 GPa indicating a high content of sp2 bonds. The vacuum electronic properties of the films were checked in an UHV chamber in a plane to plane set-up. To localize the emission sites the excitation of a low voltage phosphor (ZnO:Zn) was monitored by a CCD camera. After an activation by vacuum arc discharges emission of electrons occurred at macroscopic electrical fields as low as 3.2 V/μm. The discharges generate delaminated a-C:N film fragments that bear the FE current due to field enhancement. Discharge and therefore FE only took place at the edges of the emitter stripes due to a macroscopic field enhancement. Two kinds of activation were found leading to different microstructures of the emitter and different FE characteristic. The influence of substrate bias, nitrogen content, film thickness and emitter geometry on the field emission was also surveyed.