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

Manodiamond (ND) powder coatings are very promising for cold cathode: appli cations. The suitability:Of a (di)electrophoretically: deposited ND coating (crystallite size:1-10 nm) for high current applications was analyzed depe nding on three types of Si substrates (flat, rough, Si tip array). Nondestr uctive direct current field emission (FE) investigations were performed by means of a field emission scanning microscope: FE properties like the elect rical onset field strength E-on (at 0.5 nA), current I vs E behavior, maxim um current carrying ability as well as the local distribution and uniformit y 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 fla t to 67/44/20 V/mu m of the rough, and to approximate to 7/6.7/4.5 V/mu m o f 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 rou ghness results, however, in a low J(REP) for large areas. In contrast, ND c oated tips showed a good uniformity over mm(2) size and a moderate J(REP)ap proximate to 0.2 A/cm(2) basing on about 40% of significantly emitting-tips . (C) 1999 American Vacuum Society. [S0734-211X(99)03302-8].