Pulsed-laser-deposited and plasma-polymerized polytetrafluoroethylene (PTFE)-like thin films:: A comparative study on PTFE-specific properties

Glass-like and structural first-order phase transitions are investigated in polytetrafluoroethylene (PTFE) foils and PTFE-like films prepared by pulsed-laser deposition (PLD) and plasma polymerization (PP). A structural comparison of the investigated polymers is performed by infrared spectroscopy and dielectric dilatometry. It is shown that dielectric dilatometry (the measurement of the susceptance vs. temperature) provides a simple and elegant means for detecting volumetric transitions in thin nonpolar polymer films. In conventional PTFE foils, the known glass-like and structural first-order phase transitions are identified. The structure of pulsed-laser deposited PTFE strongly depends on the target material, ranging from highly crystalline films showing only structural phase transitions to films strongly deviating from PTFE foils, with structural characteristics comparable to plasma-polymerized fluorocarbons. The dielectric loss of the highly crystalline PLD films compares favorably with conventional PTFE foils, making the films attractive for new applications in miniature electret devices. (C) 1999 John Wiley & Sons, Inc.