Integral and local field emission analyses of nanodiamond coatings for power applications

Nanodiamond (ND) powder coatings are very promising for cold cathode applications. The suitability of a (di)electrophoretically deposited ND coating (crystallite size: 1–10 nm) for high current applications was analyzed depending on three types of Si substrates (flat, rough, Si tip array). Nondestructive direct current field emission (FE) investigations were performed by means of a field emission scanning microscope. FE properties like the electrical onset field strength Eon (at 0.5 nA), current I vs E behavior, maximum current carrying ability as well as the local distribution and uniformity of emitters were analyzed by using anodes of different apex diameters D. A decrease of Eon for D=10/100/1000 μm from 203/190/109 V/μm of the flat to 67/44/20 V/μm of the rough, and to ≈7/6.7/4.5 V/μm of the tip array sample is achieved by the geometrical field enhancement of the structures. The reproducible high-current density JREP>15 A/cm2 for D=10 μm of the flat and rough sample exhibits the large potential of the...