Abstract
We studied the elastic constant of the epitaxial Pt ultrathin films deposited using RF magnetron sputtering on MgO(001) monocrystal substrates heated at 500℃. We measured the film thickness by the X-ray reflectivity technique (XRR), and determined the normal elastic constant C_<33> of the films by the picosecond-laser ultrasounds (PSLU). The elastic constant depends on the film thickness, and the value of 20 nm films is larger than that of 90 nm by 50 %. The normal strain determined by X-ray diffraction(XRD) measurement is less than 0.1 %, which fails to explaine the elastic behavoir. Thus, we observed extraordinary increase of the elastic constant of epitaxial ultrathin Pt films.
