SCANNING-TUNNELING-MICROSCOPY OF RF OSCILLATING SURFACES

Amplitude and phase of high frequency surface acoustic wave (SAW) fiel ds are investigated by a novel scanning tunneling microscopy technique . The gap voltage is modulated at a slightly detuned high frequency. D ue to the nonlinearity of the tunneling process a frequency mixing app ears. For scanned areas with dimensions much smaller than the waveleng th of the SAW a remarkable local variation of amplitude and phase of t he tunneling current at the difference frequency is observed. Dependin g on the local morphology different components of the particle displac ement vector are detected. Model calculations of amplitude and phase i mages are presented for a real topography.