Tunneling acoustic microscope

A new type of microscope, which is based upon both a scanning tunneling microscope (STM) and a technique for detecting acoustic waves, is described. An acoustic wave generated in a STM's sample, by vibration of its tip, is detected by a piezoelectric transducer coupled to the sample. The amplitude of the acoustic wave corresponds to the strength of the force interaction between the tip and the sample, and is sensitive to tip-sample spacing. We have been successful in keeping the spacing constant by using a new feedback loop that holds this amplitude constant without tunneling. This method enhances the features of the STM without reducing its functions and enables simultaneous use of both force interactions and tunneling current to investigate the properties of samples. Topographies taken by the new feedback system and tunneling current images are shown.