The separate and combined effects of VUV radiation and fast atomic oxygen on Teflon FEP and silicon carbide

New results are given in continuation of a previous investigation [1] of VUV radiation on Teflon FEP and PTFE films. The changes in mechanical properties (tensile strength sigma and relative elongation at rupture epsilon) of Teflon FEP films (mainly 12.5, 25 mu m and 75 mu m, also one-side silvered Teflon FEP thermal control material 125 mu m), were measured as a result of illuminations with light from various VUV sources: resonance Xe lamp (147.0nm), Kr lamp (123.6nm), Hg lamp (184.9 and 254nm), deuterium lamps with silica window (lambda>177nm) or magnesium fluoride (lambda>115nm) in high vacuum conditions and at various temperatures of film samples (25-30 and 120-150 degrees C). Mass losses from Teflon FEP films under the separate and combined action of fast (2-4eV) atomic oxygen beam (about 1.10(16)atom/cm(2).s) and VUV light (147.0nm) from resonance Xe lamp (about 1x10(14) photon/cm(2)s) were measured. Erosion of Teflon FEP surfaces by VUV light resulted in the evolution of fluorine and fluorocarbon fragments of CnFm type (n can vary from 1 to at least 10, m less than or equal to 2n + 2) into the gas phase. These volatile products can induce etching of silicon-based materials (like Silica or SiC) or growth of fluorocarbon deposits on adjacent surfaces. These effects were studied by atomic force microscopy for SiC samples placed in the vicinity of Teflon FEP films illuminated with VUV light. A general picture is proposed to account for erosion and deterioration of mechanical properties of Teflon FEP films by VUV radiation.