PHOTODEGRADATION OF TEFLON AF1600 DURING XPS ANALYSIS

Teflon AF1600, containing perfluorinated dioxole rings, was found to b e particularly susceptible to X-ray degradation, such as that occurrin g during X-ray photoelectron spectroscopy. Because of the presence of O, the degradation mechanism is substantially different from those of fluoropolymers containing only C and F. Each atom of a given element w as found to have the same susceptibility to attack, irrespective of it s position in the repeat unit, with O at least twice as susceptible as F. At any dose between 60 W X-ray source power/5 min and 240 W/40 mi n, O was lost at an amount equal to that of F, which necessitated the breaking of two C-O bonds; O also degraded by breaking only one bond, in which case the oxygen was not lost but formed a free radical. The f ree radicals produced by the homolytic scission of C-C bonds participa ted in reactions leading to degradation and crosslinking. The product of X-ray filament emission current and the potential difference betwe en it and the X-ray anode. (C) 1998 John Wiley & Sons, Inc.