Abstract
It is observed that field emission electrons are dominantly extracted from a (100) surfaces of a molybdenum sharp needle emitter, when the surface is modified with zirconium oxide. The work function of the surface is estimated from Fowler Nordheim plots. The estimated average value is 2.1 eV, which is remarkably small compared with a commonly accepted value of work function for a ZrO/W (100) thermal field emitter, namely 2.7-2.9 eV, while the smallest reported value is 2.4 eV. It is expected that smaller values of work function are desirable for cathode materials to get fine focused electron beams, because less chromatic aberration can be realized. It should be noticed from practical view points that the reduced work function is reproduced easily by several times of flash heating after exposed to air.
