Picosecond Ultrasonic Microscopy of Semiconductor Nanostructures

We report on a picosecond ultrasonics study of nanostructures by high frequency ultrasound. A sound pulse is generated when an ultra short laser pulse is absorbed in a metal transducer film. The sound propagates across a thin layer (0.5-2 microns) of water and is then reflected from the surface of the sample being examined. The efficiency of optoacoustic detection of the reflected sound is enhanced through the use of a resonant optical cavity. We report on experiments in which sound is reflected from patterned nanostructures. In these experiments we are able to study the propagation of sound down narrow sub-100 nm channels.