Sllver, and Goldl

The attenuation length, \, of photoelectrons with kinetic energies in the range 500-1500 eV in hydrocarbon films was measured with self-assembled monolayers (SAMs) of n-alkanethiols adsorbed on copper and silver surfaces. This work extends a previous s_tudy using SAMs on gold. The fol lowing values were determined for tr : on Ag, 37 A at 1390 eV, 36 A at I I l9 eV, 35 A at I I 13 eV, 30 A at 914 eV, 29 A at 883 eV, and 24 A at 768 eV; on Cu, 40-A at l4 l0 and 1364 eV, 28 A at 918 eV, and 22 A at 554 eV. Estimates of ), obtained by using SAMs as scattering layers are more consistent than those obtained by using thin organic films fabricated by other methods. The relationship between tr and the kinetic energy (KE) of photoelectrons, over the energy range studied by using SAMs, can be fit equally well by the expressions \ = 9.0 * 0.022K8 or tr o KEp where p = 0.67 + 0.11. Bethe's equation for electron scattering in matter also relates A to KE.