Cesium coverage on molybdenum due to cesium ion bombardment

Cesium coverage due to Cs+ bombardment of a polycrystalline molybdenum surface was investigated in the incident energy range below 500 eV. When the surface is exposed to a Cs+ beam the work function decreases until steady state is reached with a total dose of less than ≊1×1016 ions/cm2. The steady state work function reaches a minimum at an incident energy of ≊100 eV and slowly increases with bombarding energy. Cesium coverage of a target is proportional to the ratio (1−β)/γ, where β is the reflection coefficient and γ is the sputter yield. This ratio is large for molybdenum because of its low mass and high binding energy. Implications of these results for H− surface conversion sources are discussed.