Jt. Dickinson et al., EVIDENCE FOR UNZIPPING REACTIONS IN THE LASER-ABLATION OF POLYTETRAFLUOROETHYLENE (PTFE), Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms, 91(1-4), 1994, pp. 672-676
We have characterized the neutral and charged species emitted by pulse
d-laser irradiation of polytetrafluoroethylene (PTFE) in vacuum at 248
nm in fluence regimes appropriate for the pulsed-laser deposition of
PTFE thin films. The time-of-flight behavior of the major neutral spec
ies is consistent with-thermal emission at temperatures where PTFE is
known to decompose thermally. The laser fluence dependence of the inte
nsity of the most intense neutral component (the C2F4 monomer) is anal
yzed in terms of a thermally activated decomposition process. Under is
othermal conditions, thermal decomposition is believed to be rate limi
ted by radical formation, with an activation energy of a few eV. In co
ntrast, the fluence dependence of the monomer intensity indicates an a
ctivation energy of about 0.9 eV - appropriate to an unzipping reactio
n rate limited by radical transport along the polymer chain.