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

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) and plasma d esorption mass spectrometry (PDMS) were used to investigate the second ary ion emission from perfluorinated polyethers (PFPE; trade name Kryt ox) having average molecular weights between 3800 and 10 800. The prim ary focus of the investigation was on comparison of peak patterns, mol ecular 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 cationize d with silver are seen up to m/z almost-equal-to 12 000. Metastable io ns are observed both in PDMS and SIMS; the parent ions decay into char ged and neutral fragments. The yields and half-lives of secondary ions emitted from multilayer samples are always larger in PDMS than in SIM S. However, the fragmentation processes observed are the same. Half-li ves 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 PDM S/SIMS is nearly constant at approximately 10.