Metal-ceramic contact angles determined by thin film techniques

A method of estimating contact angles is described in which 1000 A thick layers of metals are condensed from the vapour. If condensation takes place at temperatures greater than about 0.8 T_m the film is observed to break up into drops which are approximately segments of spheres, and the contact angle may be calculated from measurements on the drop size when the average film thickness is known. The experimental method is straightforward and relatively very fast, yet gives results in good agreement with earlier measurements. Results for the following metals on sapphire are presented: Al, Ag, Au, Cu, In, Sn. In addition results for Al on quartz are discussed, and it is suggested that the method may give meaningful results even when, as in this case, chemical reaction takes place.