Origin of the field-stimulated exoelectron emission from tungsten tip surfaces

Emission characteristics of the field-stimulated exoelectron emission (FSEE) from tungsten surfaces and the effect of gas adsorption on the FSEE have been investigated. The clean tungsten tip surfaces were prepared using the field evaporation technique. The clean tungsten surfaces thus prepared did not liberate FSEE. Physical adsorption of the residual gas atoms at the tungsten surface resulted in FSEE. An obvious enhancement of the FSEE signal due to gas adsorption was observed in which no significant change of the field emission pattern was caused. Therefore, FSEE is thus revealed the high sensitivity to the surface conditions.