Aluminium Surface Activation Using Atmospheric-pressure Plasma

Contact angles and Attenuated Total Reflection FTIR measurements were performed to study plasma activation of aluminium surface in air atmosphere using Diffuse Coplanar Surface Barrier Discharge plasma source. Two types of aluminium surfaces were used: i) industrially produced bulk aluminium samples; ii) thermally evaporated thin films of aluminium on glass (sets of 400 nm and 2 μm thickness). It was shown by means of Attenuated Total Reflection FTIR that plasma activation in air created functional –OH groups on the surface. Additionally, aging effect of plasma activation was measured. Introduction Surface plasma processing is one of the most rapidly growing and widely used technique. We can define plasma processing as a plasma-based material processing technology that aims at modifying the chemical and physical properties of a surface [http://en.wikipedia.org/wiki/Plasma_processing]. Wide range of control parameters (configuration, type of discharge, plasma parameters etc.) allows use plasma for completely different applications (such as etching, cleaning, activation, functionalization, passivation, deposition etc.) and for different surfaces (polymers, semiconductors, textiles, metals, metal oxides etc.). In spite of that, active research work and new areas of applications continue to appear nowadays. The aim of present work is to make general overview of plasma activation of surfaces and show some results of aluminium surface activation by Diffuse Coplanar Surface Barrier Discharge (DCSBD) [Černák et al., 2003], [Šimor et al., 2002]. Plasma activation can be defined as the process done with the intent to alter or improve adhesion properties of surfaces prior to coating, painting, deposition etc. Quite often the term plasma functionalization is used because one of the way improving surface properties prior deposition is to clean and create particular functional groups (-OH, -CO, -NO and others). It is very important when either substrate or deposited layer has polymer structure. These groups could play a role of deposition centres [Ritala et al., 1999]. As mentioned above, plasma activation can be used for different types of surfaces: • polymer surfaces [Mittal, 2000]. Main aim of plasma activation of polymer surface is creation of functional groups and cross-linking the polymer lines to stabilize the surface properties. Functional groups play significant role of increasing wettability of surface for paintings and coatings, which is very crucial for industry applications. Cross-linking is the process of cross bond creation between polymer chains. This process can dramatically change mechanical surface properties and also leads to changes in surface free energy; • metal surfaces. Adhesion between metal surface and polymer surface is one of the important problems for industrial applications of anticorrosion coatings. One of possible ways to improve anticorrosion resistance is to cover the metal surface with protective layer [Fracassi et al., 2003], [Domingues et al., 2002]. Intensive research work on organosilane coatings is studied nowadays [Franque et al., 2004]; • semiconductor surfaces. Plasma activation process is studied and used in wafer bonding process [Suni et al., 2003], which is extremely important due to development of microelectronics from bulk to “semiconductor-on-insulator” technology. For this purpose very uniform and gentle surface activation processes are required: on one hand it should not dramatically change the roughness, on the other hand it should clean and create dense number of functional groups on the surface; • metal oxide surfaces, dielectrics. It is industrially important to cover surface by other layer [Akbulut 182 WDS'09 Proceedings of Contributed Papers, Part II, 182–187, 2009. ISBN 978-80-7378-102-6 © MATFYZPRESS