A Novel Plasma Technique for Surface Treatment: The Plasma Expander

This paper describes a new plasma treatment method: the plasma expander. In this approach, expanding shock waves are generated in a vacuum chamber by pulsed plasmas. Collisions of fast species in the waves modify the properties of solid surfaces exposed to the plasma. The degree of such modification is governed by the energy delivered by the plasma exposure. To confirm the efficacy of this approach, modifications induced in the properties of thin polymer films produced by plasma-enhanced chemical vapor deposition by exposure to nitrogen plasma shock waves were investigated. The films were prepared from benzene radio frequency plasmas and subsequently exposed to different quantities of nitrogen shock waves Nw. The effects of Nw on the wettability, molecular structure, and mechanical properties of the films were studied. Fourier transform infrared spectroscopy revealed that greater Nw resulted in the loss of C-H groups and the rupture of benzene aromatic rings observed in the structure of the as-deposited films. Furthermore, the contact angle strongly increased and the hardness, evaluated by nanoindentation, increased up to fourfold with the increase in the intensity of the treatment.