Cr. Davis et al., STRUCTURAL-MODIFICATION MECHANISM FOR POLYIMIDE-DOPED POLY(TETRAFLUOROETHYLENE) AT SUBTHRESHOLD FLUENCES USING 248 NM RADIATION, Journal of applied physics, 76(5), 1994, pp. 3049-3051
Single-photon excimer laser ablation of neat poly(tetrafluoroethylene)
(PTFE) is not observed at emissions in the ''quartz'' UV, i.e., from
about 190-380 nm. However, it has been successfully demonstrated that,
when the fluoropolymer is doped with small quantities of polyimide (P
I), ablation in the quartz UV, e.g., at 248 and 308 nm and pulse width
s of about 25 ns, is readily achieved. When PI-PTFE blends are exposed
to subthreshold fluences, considerable changes in surface topography
occur although clearly defined structures, e.g., pits, are not formed.
Using photoacoustic infrared spectroscopy to evaluate surface and bul
k chemical changes to blends exposed to subthreshold excimer laser flu
ences, <100 mJ/cm2, it is shown that PI (1) is distributed throughout
the bulk and resides at the surface and (2) is selectively absorbing t
he high-energy photons and as a result being preferentially removed fr
om the surface.