Adsorption of residual gas molecules damped the emission current of a W (310) field
electron emission (FE) emitter. The damping speed was linearly proportional to the pressure
gauge readings at pressure ranging from ∼10-8 Pa to ∼10-9 Pa, and the proportionality
constant was employed to measure pressure in the 10-10 Pa range. A time plot of FE current
revealed the existence of an “initial stable region” after the flash heating of W(310) FE,
during which the FE current damps very slowly. The presence of non-hydrogen gas removed
this region from the plot, supplying a means of qualitatively analysing the gas species.

Keywords: Pressure, Field electron emission, Adsorption, Work function, Extreme high vacuum