Effect of the air-plasma pre-treatment of the substrate on the tribological properties of UHMWPE thin films coated onto Si

摘要

Silicon (Si) is one of the widely used materials in microelectromechanical systems (MEMS) and microsystems. However, bare Si exhibits high friction, adhesion and wear, without proper surface modification. Several types of ultra-thin films have been proposed recently, which improved the tribological properties of Si [1, 2]. One important category of these films is the polymer coatings, which have found their use in various tribological applications [2]. However, these polymer coatings often suffer from poor adhesion to the substrate thus resulting in low wear life. Various pre-treatment processes such as piranha treatment have been used to enhance the adhesion property of the Si substrate and the polymer film. Piranha treatment, besides using environmentally harmful chemicals such as hydrogen peroxide and sulphuric acid, is a laborious process involving long reaction time. Air-plasma treatment has proven to be a very cost effective and an environmental friendly process which influences the surface cleanliness, the chemical functionality and the topography of the treated substrate. Therefore, in the present study the effect of pre-treatment of Si (piranha and plasma treatments) on adhesion strength between UHMWPE film and Si and tribological properties of UHMWPE film on Si is evaluated.