Study of the mechanical and microstructural state of platinum thin films

The microstructural and mechanical state of polycrystalline Pt thin films deposited by electron beam evaporation on oxidised Si substrates have been characterised using an X-ray diffraction diffractometer and a vibrating-reed device. The conventional sin(2) psi method shows that films exhibit tensile residual stresses and the value of the unstrained lattice parameter is lower than the bulk one. The size of the coherently diffracting domains (approximate to 5 nm) and microdistortions (0.3%) in a 150 nm thick film are obtained using the Warren-Averbach and integral width methods. Internal friction has been measured between 300 K and 800 K during thermal cycling, showing that the damping level is considerably reduced by annealing between 650 K and 800 K. Thanks to isothermal experiments, we have determined the activation enthalpy of the process involved in the structural evolution. The calculated energies and complementary micrographs (TEM) enable us to assume that the observed mechanism is closely related to microstructural rearrangements located at grain boundaries.