Particles in laser ablation of polytetrafluoroethylene

KrF-laser ablation of pressed polytetrafluoroethylene (PTFE) targets is accompanied by the ejection of submicron- to micron-sized particles. Collected ejecta consist of four basic particle morphologies ranging from small particles 50-200 nm in diameter to larger particles similar to 10 mu m in diameter. Many particles carry electric charge as measured by using charged electrodes and by the Millikan technique. Thin PTFE films deposited by pulsed laser deposition (PLD) from the same targets onto heated Si substrates are highly crystalline and show only a minor but detectable increase of defects compared with the target material. The transferred particulates mainly consist of long PTFE molecule chains. The low molecular weight material that is also transferred to the substrate mainly either links with other low molecular weight material or evaporates during deposition.