ON THE NATURE OF STRUCTURAL RELAXATION IN AMORPHOUS AS2S3

We have measured the low-frequency elastic properties of amorphous As2S3-films in the temperature range from 8 mK to 350 K. The samples investigated were treated in four different ways: as-evaporated, illuminated, annealed, and both annealed and illuminated. Around 270 K a huge peak was observed in the internal-friction measurement which was strongly influenced by the sample treatment. In contrast, the behaviour at low temperatures was not affected by the light- and thermally induced structural changes, suggesting that the tunneling entities of the relevant systems are built up by a relatively large number of atoms.