ELECTRON-STIMULATED DESORPTION OF POTASSIUM AND CESIUM ATOMS FROM AN OXIDIZED MOLYBDENUM SURFACE

The yield and energy distributions of potassium and cesium atoms emitt ed in electron-stimulated desorption (ESD) from a molybdenum surface, oxidized to different extent and maintained at 300 K, have been measur ed by the time-of-flight technique with a surface ionization detector. The ESD threshold for potassium and cesium atoms lies around 25 eV, i rrespective of molybdenum oxidation state. In the case of molybdenum c oated by an oxygen monolayer, secondary thresholds at similar to 40 an d similar to 70 eV have been observed, as well as atomic energy distri bution tailing down to very low energies. The most probable kinetic en ergies of the atoms are a few tenths of one eV. The results are explai ned within a model involving Auger neutralization of the adsorbed alka li metal ions after the filling of the 2s O, 4s Mo, and 4p Mo core hol es. The possibility of ESD of a neutral species as a result of oxide-c ation core-level ionization has been demonstrated for the first time. (C) 1997 American Institute of Physics.