XPS and QCM Studies of Hydrocarbon and Fluorocarbon Polymer Films Bombarded by 1−20 keV C₆₀ Ions

Poly(methyl methacrylate) or PMMA, Teflon AF1600, and poly(3-hexylthiophene) films are studied after bombardment with different fluences of C 60 ions with energies of 1−20 keV by a quartz crystal microbalance (QCM) and X-ray photoelectron spectroscopy (XPS). C 1s XP spectra show little or no change in the film chemistry upon ion bombardment up to 10 13 −10 14 ions/cm 2 . This result supports prior observations from secondary ion yields that at least some organic films have no apparent static limit in secondary ion mass spectrometry (SIMS) using C 60 ion projectiles until the film is sputtered away. Changes in C 1s XP spectra observed at the highest ion energies and fluences >10 15 ions/cm 2 are explained predominantly by differential charging effects. Some changes in film composition are also observed, but their extent varies with the polymer studied. Measurements for the total sputter yield of films acquired using a QCM show that each C 60 cluster leads to an efficient emission of ∼10 5 amu per C 60 ion at 20 keV impact. The energy dependence for the total sputtering yield changes from a power law (with n ∼ 1.4) to linear after 5−10 keV. The sputtering yield at >10 keV of polymer films shows total enhancement of ∼5 times higher compared with gold targets.