THE SEPARATE AND COMBINED EFFECTS OF VUV RADIATION AND FAST ATOMIC OXYGEN ON TEFLON FEP AND SILICON CARBIDE

摘要

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 a and relative elongation at rupture e) of Teflon FEP films (mainly 12.5, 25μm and 75μm, also one-side silvered Teflon FEP thermal control material 125μm), were measured as a result of illuminations with light from various VUV sources: resonance Xe lamp (147.0 nm), Kr lamp (123.6nm), Hg lamp (184.9 and 254nm), deuterium lamps with silica window (λ>177nm) or magnesium fluoride (λ>115nm) in high vacuum conditions and at various temperatures of film samples (25-30 and 120-150°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 (147.0 nm) from resonance Xe lamp (about 1×10~(14) photon/cm~2s) were measured. Erosion of Teflon FEP surfaces by VUV light resulted in the evolution of fluorine and fluorocarbon fragments of C_nF_m type (n can vary from 1 to at least 10, m≤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.