Abstract
We have used a focused electron beam to scan the surface of a substrate sample. The resulting electron induced desorbed ion is mass analyzed and the signal thus obtained is used to intensity modulate an output display. This technique enables us to obtain spatial distribution information of the adsorbed species. We have used this technique to monitor the spatial distribution of the F+ signal desorbed by electron interaction with a tungsten ribbon substrate. Results obtained indicate considerable surface migration of the fluorine or more probably the fluorine containing molecule. Rapid (flash) heating causes primarily thermal desorption while slow heating results in rapid surface migration to the sample support rods.