SCANNING ACOUSTIC TUNNELING MICROSCOPY AND SPECTROSCOPY - A PROBING TOOL FOR ACOUSTIC SURFACE OSCILLATIONS

A method is presented for the universal probing of surface acoustic wa ves (SAWs). For measuring high frequency SAWs by scanning tunneling mi croscopy (STM) a stroboscopic snapshot technique was employed, named s canning acoustic tunneling microscopy. The amplitude and the phase of a state of oscillation within a SAW field are a superposition of the s urface topography and the oscillation trajectory. Measuring with atomi c resolution the observed contrast can be understood by a spherical tu nneling model. A STM based system is proposed that reaches submicron r esolution for the quantitative evaluation of elastic constants. With t his system the velocity dispersion is obtained from the detection of l aser generated SAW pulses by a broadband STM. Scanning acoustic tunnel ing spectroscopy using different acoustic modes opens a door for quant itative studies of nanoscale structures. (C) 1997 American Vacuum Soci ety. [S0734-211X(97)10004-X].