The internal friction of a 4-thick free-standing film was investigated. At a measuring frequency of about 200Hz, a relaxation peak was found near to 100C. When compared with a substrate-bonded film which had the same columnar microstructure, the peak was some 3 times higher but the temperature position was the same. This confirmed a model, developed for substrate-bonded films, which assumed that intrinsic grain boundary sliding controlled the relaxation mechanism. The film/substrate bonding affected only the peak height, but partially hindered grain boundary sliding and thus reduced the relaxation strength.

D.Heinen, H.G.Bohn, W.Schilling: Journal of Applied Physics, 1995, 78[2], 893-6