Properties of Evaporated MgF2 Thin Films Influenced by the Plasma Treatments of the PMMA Substrates
1988 Volume 9 Issue 5 Pages 350-355
Details
1988 Volume 9 Issue 5 Pages 350-355
The effect of a low temperature plasma treatment on the surface properties of polymethylmethacrylate (PMMA) was investigated. The adhesion strength of MgF2 thin film deposited on the treated surfaces was studied in detail.
PMMA substrates were treated in an rf (13.56MHz) plasma reactor, then MgF2 thin film was physically deposited on the treated PMMA substrates. The experiment was carried out for 4 types of source gases, O2, N2, Ar, and H2. The adhesion strength of MgF2 thin film was measured by means of a topple test.
The adhesion strength increased significantly after a few minute plasma treatment, particularly with O2 source gas. The formation of oxgen containing groups on the treated PMMA surface was identified by XPS analysis. The decrease of the water contact angle (θ) on the treated surface was also observed, and the adhesion strength was proportional to cos θ. The additional treatment decreased the adhesion strength in spite of the increase in cos θ. It is identified by XPS analysis that a weak layer is formed just below the surface of additionally treated PMMA. This may be caused by the damage on the main chain of PMMA by UV radiation during the treatment.
