Temperature dependence of the work function of a ZrO/W Schottky electron source

Measurements of the work function of a ZrO_x/W(100) Schottky electron source in operation vary between 2.5 and 3.0 eV. Results show the work function has an approximately linear dependence on temperature with a positive coefficient between 0.5 and 0.7 meV/K on field and temperature range. Also, the theoretical reduced brightness of the electron source is shown to be slightly dependent on temperature. This would mean that Schottky sources of this type can be operated at lower temperatures, improving the stability of the tip shape without losing very much in brightness