STUDY OF THE MECHANICAL AND MICROSTRUCTURAL STATE OF PLATINUM THIN-FILMS

The microstructural and mechanical state of polycrystalline Pt thin fi lms deposited by electron beam evaporation on oxidised Si substrates h ave 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 unstraine d lattice parameter is lower than the bulk one. The size of the cohere ntly 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 3 00 K and 800 K during thermal cycling, showing that the damping level is considerably reduced by annealing between 650 K and 800 K. Thanks t o isothermal experiments, we have determined the activation enthalpy o f the process involved in the structural evolution. The calculated ene rgies and complementary micrographs (TEM) enable us to assume that the observed mechanism is closely related to microstructural rearrangemen ts located at grain boundaries.