ELECTRON-STIMULATED DESORPTION OF OXYGEN-ATOMS AND IONS FROM AN OXIDIZED AG-ZR ALLOY SURFACE

Electron stimulated desorption (ESD) is a complex process in which the ion and neutral yields are functions of many variables. In order to examine some of these dependencies which have not been considered previously, a study of the composition and ESD behavior of a Ag/0.5wt%Zr (Ag 0.5 Zr) alloy membrane has been conducted. Zr was added to the Ag primarily to increase the O concentration at the surface and thereby enhance the ESD signal. The surface was sputter cleaned, saturated with O2, sputter cleaned again and then annealed at 250-degrees-C until no further changes occurred in the surface composition according to ion scattering spectroscopy (ISS) and Auger electron spectroscopy (AES). ISS data suggest that the resulting surface consists of islands of Zr oxide partially covering the Ag surface. Neutrals emitted in ESD are quite difficult to detect so a technique was developed to determine the 0 neutral-to-ion ratio of 1.1 X 10(7) for a primary beam energy of 1 keV. By monitoring the surface O concentration as a function of time with AES, a total ESD cross section of 3.9 x 10(-19) cm2 was determined. The ESD O+ energy distribution spectrum was obtained and compared with that obtained from O-charged Ag. Also, the effect of primary beam incidence angle on the ESD yield and ion energy distribution was examined and found to be significant.