Studies of techniques for preparing zinc oxide-coated tungsten microem
itters, their emission characteristics and the stability of their emis
sion currents have been recently published, in this paper, the influen
ce of thermal treatment of the cathode while the emission current leve
l is similar to 10 mu A has been investigated. At temperatures of simi
lar to 700 degrees C the current showed a considerable increase in val
ue for the same applied anode voltage. Though the anode voltage was re
duced by approximately 25-30% the cathode produced the same emission c
urrent. It is believed that this enhancement is caused by the release
of gases, mainly oxygen, from the composite tip, and there is also the
possibility of bombardment from the anode screen by phosphor atoms (a
nd conceivably other atoms too). The behaviour of the cathode as well
as its current-voltage (I-V) characteristics resembled the well known
thermal field-forming process, although the effect on the current emit
ted was smaller. The enhancement in the emission current has been show
n experimentally to be permanent and to produce reversible I-V charact
eristics The change in the I-V characteristics indicate that relativel
y large changes in the work function of the ZnO-W composite cathode ha
ve taken place.