Number 419 (Story #1), March 19, 1999 by Phillip F. Schewe and Ben Stein|
NANOMETER-SCALE IMAGES OF SOUND WAVES on surfaces have been achieved by several groups, enabling researchers to observe oscillations of single atoms and promising ordinarily difficult-to-obtain nanoscopic information on material properties beneath the surface. At this week's international joint meeting in Berlin of the Acoustical Society of America, the European Acoustics Association, and the German Acoustical Society (ASA/EAA/DAGA '99), Ute Rabe of the Frauenhofer Institute for Nondestructive Testing in Germany (firstname.lastname@example.org) showed that such images are possible by generating ultrasound waves on a surface and detecting them with a scanning probe microscope. Eduard Chilla of the Paul Drude Institute in Berlin (email@example.com) used atomic force microscopy techniques to image insulators and a scanning tunneling microscope to image conductors. The STM in particular could record oscillations of single atoms responding to a sound wave. Using an AFM in various operating modes, Andrew Kulik of the Federal Polytechnic Institute of Lausanne, Switzerland (firstname.lastname@example.org) showed images of sound waves coursing through a tin sample. Different features in the image corresponded to regions of increased stiffness or flexibility, and likely were the sites of grain boundaries in the tin sample. In general, these techniques can potentially provide nanoscopic details on the elastic properties of a material and other subsurface information, such as the stress between different layers of a material.