Particles in laser ablation of polytetrafluoroethylene

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