Thickness and energy dependence of secondary ion emissions from Langmuir-Blodgett films

Using Cd arachidate films formed on Ag and Si substrates, secondary ion intensities were investigated by TOF-SIMS. The intensities of [M + H](+), [M + Cd](+) and Ag cationized ions from samples on the Ag and Si substrates were found to change as a function of LB film thickness, as well as the primary beam energy. The intensities of [M + H](+) and [M + Cd](+) were seen to be (1) the highest at a one-layer LB film, (2) to decrease as the LB film becomes thicker, (3) change slightly with the primary ion beam energy. On the other hand, the intensities of Ag cationized secondary ions were almost constant with the changes of LB thickness and the energy of the primary ion beam, after normalized by Ag+ intensity. The results were discussed in terms of the energy transfer of the primary beam to the LB films, the property of the substrate materials, and the strength of chemical bondings. (C) 1999 Published by Elsevier Science B.V. All rights reserved.