  We have investigated surface shear waves at 22 MHz in a 0.5-micron-thick
polymer film on SiO2/Si substrate at low temperatures using suspended and
non-suspended graphene as detectors. By tracking ultrasound modes detected by
oscillations of a trilayer graphene membrane both in vacuum and in helium
superfluid, we assign the resonances to surface shear modes, generalized Love
waves, in the resist/silicon-substrate system loaded with gold. The propagation
velocity of these shear modes displays a logarithmic temperature dependence
below 1 K, which is characteristic for modification of the elastic properties
of a disordered solid owing to a large density of two level state (TLS)
systems. For the dissipation of the shear mode, we find a striking logarithmic
temperature dependence, which indicates a basic relation between the speed of
the surface wave propagation and the mode dissipation.
