IMAGING OF SURFACE ATOMS REVOLVING ON ELLIPTIC TRAJECTORIES

Achieving atomic resolution with an STM demands a noise-free environme nt, where mechanical vibrations especially must be damped out. Introdu cing such vibrations in the form of defined ultrasound consequently le ads to image distortion. In particular, the topography is smeared out. By employing surface acoustic waves, which lead to an oscillation of surface atoms on elliptically polarized trajectories, this smearing-ou t is directed, thereby giving a projection of the ellipse on the sampl e plane. However, by employing a stroboscopic heterodyne technique (mi xing the high-frequency tunneling current with a slightly detuned elec trical signal which is applied across the tunneling gap) a snapshot of the surface oscillation is seen. We present phase and amplitude image s exhibiting atomic resolution. The atomic contrast of phase and ampli tude is explained by the superposition of the surface topography and t he oscillation trajectory, which can be obtained from a continuum theo ry model.