Electron field emission from Ti-containing tetrahedral amorphous carbon films deposited by filtered cathodic vacuum arc

Titanium-containing tetrahedral amorphous carbon (ta-C:Ti) films with different titanium content were deposited by a filtered cathodic vacuum arc technique. The microstructure of these films was confirmed to be of ta-C+TiC_x(x<1) nanocomposite by Rutherford backscattering spectroscopy, x-ray diffraction, and micro-Raman spectroscopy experiments. With the increase of titanium content, the titanium carbide content increased and the sp³ fraction in the residual ta-C phase decreased gradually. In the electron field emission tests, it was found that proper conditioning processes are necessary for all these films in order to get a steady reproducible emission behavior. After conditioning, the emission threshold field of the films is about the same value, around 10 V/μm, except for the film with the lowest titanium content (∼1.2 at%) of which the threshold field is much higher, around 17-18 V/μm. The optimum titanium concentration in the film for field emission, showing the highest emission current and emission site density, is about 12 at%. After field emission testing, graphitization was involved and the titanium carbide phase, at least some of the sub-stoichiometric TiC_x phase, in the ta-C:Ti films decomposed.