Matrix effects in the work-function dependence of negative-secondary-ion emission

The effects of a surface electric dipole layer on the emission of negative secondary ions from clean and oxidized Si(111) surfaces have been studied under static-mode, 500-eV ${\mathrm{Ne}}^{+}$ bombardment. For clean Si(111) surfaces, the work-function $\phi$ dependence of the emission of ${\mathrm{Si}}^{-}$ is independent of whether Cs or Li adatoms are used to create the dipole layer. However, in the presence of an oxygen matrix, the $\phi$ dependence of ${\mathrm{Si}}^{-}$ emission is altered from the clean Si case and is dependent on the particular alkali dipole layer used, illustrating the importance of matrix effects in negative-ion emission.