Pulsed-laser deposition of crystalline Teflon (PTFE) films

Thin films of crystalline polytetrafluoroethylene (PTFE) were prepared by pulsed-laser deposition using 248 nm UV-excimer-laser radiation. Pressed powder pellets and bulk PTFE have been employed as target material. The films were analyzed by means of optical polarization microscopy, stylus profilometry, capacity measurements, XRD, and IR spectroscopy. The effect of substrate temperature Ts on the morphology and crystallinity of the films was studied. Films deposited from pressed powder targets at sufficiently high Ts consist mainly of spherulite-like microcrystallites. These films are continuous, pinhole-free, well adherent to the substrate, and have a composition which is similar to that of the target material. It is suggested that film formation is based on laser-assisted material transfer with subsequent melting and crystallization. They are superior to films deposited from PTFE bulk targets, cut from a solid rod, with respect to film morphology, deposition rate, film cohesion, and optical and electrical properties.