Direct visualization of the oscillation of Au(111) surface atoms

A high frequency oscillating Au (111) surface was measured with atomic resolution using a modified scanning tunneling microscope. On the atomic scale propagating surface acoustic waves lead to oscillations of atoms on elliptical trajectories, with the axes being determined by the material parameters of the surface. Since those oscillation frequencies are much higher than the scan frequencies the topography contrast is reduced. This basic problem is solved by measuring a stroboscopic snapshot seeing a defined state of oscillation. The atomic resolution of the phase and the amplitude contrast is explained by the superposition of the surface topography and the oscillation trajectory. (C) 1996 American Institute of Physics.