SECONDARY-ION EMISSION FROM PERFLUORINATED POLYETHERS USING MEGAELECTRONVOLT AND KILOELECTRONVOLT ION-BOMBARDMENT

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) and plasma desorption mass spectrometry (PDMS) were used to investigate the secondary ion emission from perfluorinated polyethers (PFPE; trade name Krytox) having average molecular weights between 3800 and 10 800. The primary focus of the investigation was on comparison of peak patterns, molecular secondary ion yields, and stabilities of secondary ions formed by kiloelectronvolt (SIMS) and megaelectronvolt (PDMS) ion bombardment. Although both techniques produce the same secondary ion species from multilayer samples, secondary ion emission from monolayer PFPE films deposited on silver is observed only for SIMS; oligomer ions cationized with silver are seen up to m/z almost-equal-to 12 000. Metastable ions are observed both in PDMS and SIMS; the parent ions decay into charged and neutral fragments. The yields and half-lives of secondary ions emitted from multilayer samples are always larger in PDMS than in SIMS. However, the fragmentation processes observed are the same. Half-lives are independent of mass in the mass range studied. The yield ratio for ions in PDMS and SIMS is an apparent function of mass because of ion half-lives. When half-lives are considered, the yield ratio of PDMS/SIMS is nearly constant at approximately 10.