Acoustic microscopy beyond the diffraction limit: an application of microfabrication

The critical components of a scanning near-field acoustic microscope have been microfabricated. A ZnO ultrasonic transducer is used to launch 175 MHz acoustic waves down a sharp silicon tip. Imaging can be done by raster scanning the tip over a sample while monitoring the transmitted acoustic signal. Initial experiments indicate the height sensitivity of the microscope is approximately 20 AA. One-dimensional scans show that the lateral resolution is approximately 800 AA. The exact nature of the interaction of the tip and sample is not well understood but repeated scans over the same region of a sample do not result in noticeable sample damage. The authors intend to use this microscope to image samples such as organic films and microfabricated structures.<>