SEM study of fluorocarbon films by R.F. sputtering PTFE targets on PET substrates

Abstract The R.F. sputtering technique was used for developing a novel waterproof and breathable fabric. In this paper, as the first step, fluorocarbon films were deposited by R.F. sputtering PTFE targets on PET substrates. At the early stage, the surface microstructure of these films obtained at various energies was examined. It was found by SEM that some segregated grains deposited on the PET substrates tended to be finer, closer, more uniform and more round with increasing energy. The explanation seems to be that the critical size decreased, the activation point on substrate increased, and the grain destruction was promoted with increasing power. The surface microstructure of these films, obtained with a power of 800 W, for various deposition times was observed. The typical deposited film consisted of several semi-continuous sublayers by three-dimensional (3-D) island growth mode. However, the growth by 3-D mode seems to be not thorough: the end structure of every sublayer was semi-continuous and consisted of numerous lying silkworm-like islands (of the order of 100 nm) joining each other. As a whole, the film other than the monolayer grew sublayer by sublayer and finally formed a three-dimensional network structure. When the underlayer grew, some grains of the next several sublayers on it had deposited gradually and started to grow. For every sublayer, once the coverage reached 50–70% the sublayer no longer continued to grow.