ASSESSMENT OF DIFFUSION-PROCESSES IN THIN-FILMS

Thin spectrally selective solar absorber coatings have to be prevented from degradation caused by the substrate acting as a diffusion source . The effect of an intermediate layer sputtered in between the substra te and the absorber layer was investigated. The samples were tested un der high-temperature exposure and under air and vacuum conditions meas uring the solar absorptance and the emittance. Auger electron spectros copy (AES) depth profiling studies were performed in order to investig ate the changes of the element concentration caused by the ageing proc ess. The behaviour of the diffusion barrier was examined in a two-laye r system. A mathematical model for the grain boundary diffusion was de veloped and compared with the experimental results. (C) 1998 Published by Elsevier Science B.V. All rights reserved.