The scanning acoustic tunneling microscope is based on the conventional sca
nning tunneling microscope and extends its topography-mapping capability to
the investigation of both amplitude and phase of surface acoustic waves (S
AWs) with frequencies in the MHz range. The mechanical oscillation of the s
urface induced by the SAW modulates the tunneling current. By adding a sinu
soidal high frequency signal to the dc tip voltage this ac tunneling curren
t signal is mixed down to an easily detectable low frequency signal. Here,
we report the first ultrahigh vacuum (UHV)-compatible version of this techn
ique including provision for sample transfer and in situ surface preparatio
n. Since both signal-to-noise ratio and spatial resolution are significantl
y enhanced in UHV, acoustic oscillations of topography features can be inve
stigated on the nanoscale. At present, SAW frequencies up to 400 MHz have b
een successfully fed into the UHV system. (C) 2001 American Vacuum Society.