FIELD-EMISSION AND ATOM-PROBE FIELD-ION MICROSCOPE STUDIES OF PALLADIUM-SILICIDE-COATED SILICON EMITTERS

Palladium-silicide-coated field emitters were prepared by palladium thermal evaporation onto silicon tips, followed by annealing at 675 K. Pulsed laser atom probe analysis is showed a clean near stoichiometric, Pd2Si layer with a thin silicon-enriched surface. In spite of the higher work function of palladium silicide compared to silicon, enhanced emission was obtained from the silicide-coated tips. Field ion and field emission imaging of the tips showed that this enhanced emission was due to the roughness of the silicide layer. Pulsed laser atom probe analysis of a palladium silicide tip exposed to air for four days showed that the silicon-rich surface layer was converted to an oxidized layer 2-4 monolayers thick. The field emission characteristics of silicide tips exposed to air were similar to those observed previously in oxidized silicon tips. After an initial current burst which corresponded to the disruption of the oxide layer, intense emission was observed from sharp areas around the circumference of the tip.