Impulsive stimulated scattering of surface acoustic waves on metal and semiconductor crystal surfaces

Impulsive stimulated scattering (ISS) is used to obtain the orientational dependence of the velocity of surface acoustic waves (SAW) on single crystal metal and semiconductor surfaces. Mechanically polished surfaces of aluminum(111), nickel(100), and germanium(100) samples were examined, as well as a comparison of mechanically polished versus high vacuum sputtering/annealing of a Ni(100) surface. The ISS technique offers an accurate and robust method of obtaining surface acoustic velocities of metal and semiconductor crystalline surfaces without physical contact. The orientationally dependent ISS results on Ni(100) are compared with recent classical Brillouin scattering measurements, and with velocities calculated using bulk elastic constant data. Finally, ISS measurements on tilted (i.e., lower symmetry surfaces) reveal coupling of the ISS excited SAW with bulk transverse modes.