MEASUREMENT OF THE LATTICE THERMAL-EXPANSION COEFFICIENTS OF THIN METAL-FILMS ON SUBSTRATES

A difference in thermal expansion between a thin film and its substrat e causes mechanical stresses in the film. Therefore, knowledge of the thermal expansion coefficients of thin films are important for their t echnological applications. In this article, we present an analysis whi ch can be used to extract the thermal expansion coefficient of a thin film material using a commonly used x-ray technique. The major advanta ge of our approach is that it is not necessary to remove the film from the substrate. The knowledge of the elastic constants of the thin fil m material and their temperature dependence is not required, which is particularly useful when thin film alloys are studied whose thermal an d elastic properties are not available. For verification of the method , we investigated thin Al films because the thermal and elastic proper ties of bulk Al are well known. The comparison of our results with the bulk properties shows a reasonable agreement, indicating the validity of the new method. (C) 1998 American Institute of Physics.