EXPONENTIAL SCALING OF SPUTTERED NEGATIVE-ION YIELDS WITH TRANSIENT WORK-FUNCTION CHANGES ON CS-BOMBARDED SURFACES()

The emission of negative secondary ions (C-, Si-, Ge-, Au-) from keV-C s--irradiated elemental surfaces was monitored during the initial stag es of Cs incorporation. Concurrently determined work-function variatio ns Delta Phi were found to be 2.75 eV for graphite, 2.3 eV for Si, 0.8 4 eV for Ge, and 0.62 eV for Au. This lowering of Phi results in an ex ponential increase of the sputtered ions' ionization probability P-. V alues of P- derived from the Delta Phi scaling are 0.19 for C-, 0.093 for Si-, 1.6X10(-3) for Ge-, and 5.7x10(-3) for Au-, and agree quantit atively with measured ion-yield data.