Polytetrafluoroethylene (PTFE) films prepared by F₂-laser deposition

Applied Physics, Johannes-Kepler University Linz, Altenbergerstr. 69, 4040 Linz, Austria

Corresponding authors: johannes.heitz@jku.at dieter.baeuerle@jku.at

Received: 30 June 2004
Accepted: 25 October 2004
Published online: 21 December 2004

Abstract

Thin films of polytetrafluoroethylene (PTFE) were prepared by pulsed-laser deposition (PLD) from bulk PTFE targets using 157 nm F₂-laser radiation. The films were analyzed by means of optical polarization microscopy, stylus profilometry, XPS, XRD, FTIR spectroscopy, and by capacitance measurements. The effect of substrate temperature, T_s, on the morphology and crystallinity of the films was studied. Films treated at sufficiently high T_s consist mainly of spherulite-like crystallites. Films with a thickness of more than about 155 nm are continuous, pinhole-free, well adherent to the substrate, and have a composition which is similar to that of the target material. The minimum film thicknesses and deposition rates are much lower than those achieved with pressed PTFE powder targets using 248 nm KrF-laser ablation. This is related to the different deposition mechanisms. Film formation based on KrF-laser ablation of pressed powder targets is mainly related to the condensation of large particulates transferred in a particle jet from the target to the substrate. F₂–laser ablation and film formation seems to be based on the ablation and condensation of small fragments. Correspondingly, the morphology, crystallinity, and the optical and dielectrical properties of films significantly differ from each other.