Young's modulus measurements and grain boundary sliding in free-standing thin metal films

Young's modulus of free-standing polycrystalline Al, Au, and W films with s ubmicron thickness has been studied using a dynamic bulge-testing technique . For Au and Al films a clear frequency dependence of the modulus is observ ed at room temperature in the range 1x10(-4)-0.5 rad/s. The values of the m oduli are considerably smaller than the corresponding values of bulk materi al. The modulus of W films measured under the same conditions does not depe nd on frequency and is equal to the bulk value. The origin of the behavior found in the Al and Au films is anelastic grain boundary sliding. As a cons equence of the relatively small grain size of thin polycrystalline films th is phenomenon is observable at room temperature in films with a relatively low melting point. (C) 2001 American Institute of Physics.