Published online by Cambridge University Press: 15 February 2011
The mechanical stress of epitaxial SrF2 and CaF2 films on Si(111) substrates has been measured as a function of temperature by the substrate curvature technique. The temperature dependence of the stress in the SrF2 film is interpreted in terms of an energy barrier to dislocation motion. When the strain energy is smaller than the value needed to overcome the barrier, the change in stress is due mainly to elastic deformation. As the temperature change increases, the strain energy becomes large enough to overcome the barrier, at which point plastic deformation initiates. Unlike SrF2, the stress behavior of the CaF2 film for increasing temperature is quite different from its behavior for decreasing temperature. This unusual behavior is not understood at this time.