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

Manodiamond (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 E-on (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 mu m from 203/190/109 V/mu m of the flat to 67/44/20 V/mu m of the rough, and to approximate to 7/6.7/4.5 V/mu m of the tip array sample is achieved by the geometrical field enhancement of the structures. The reproducible high-current density J(REP)>15 A/cm(2) for D=10 mu m of the flat and rough sample exhibits the large potential of the ND coating for power applications. Their nonuniformity due to the mu m roughness results, however, in a low J(REP) for large areas. In contrast, ND coated tips showed a good uniformity over mm(2) size and a moderate J(REP)approximate to 0.2 A/cm(2) basing on about 40% of significantly emitting-tips. (C) 1999 American Vacuum Society. [S0734-211X(99)03302-8].