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Acoustic microscopy with resolution in the NM-range

: Rabe, U.; Arnold, W.; Janser, K.

Tortoli, P.:
22st International Symposium on Acoustical Imaging 1995. Proceedings
New York, NY: Plenum Press, 1996 (Acoustical imaging 22)
ISBN: 0-306-45364-9
International Symposium on Acoustical Imaging <22, 1995, Florenz>
Fraunhofer IZFP ()
acoustic microscopy; akustische Mikroskopie; atomic force microscopy; elastic constant; elastic property; elastische Eigenschaft; elastische Konstante; Kraftmikroskopie; Nichtlinearität; nonlinearity

Different acoustical near-field microscopes have been developed, some of which combine the high lateral resolution of Atomic Force Microscopy (AFM) with Acoustic Microscopy. In one version of such instruments, a piezoelectric transducer coupled to the sample emits pulses or continuous ultrasonic waves. As a consequence, ultrasonic flexural vibrations are excited in the AFM cantilever because its sensor tip isin contact or in close proximity to the vibrating sample surface. The cantilever vibrations in a frequency region of about 100 kHz -5MHz are detected with a fast, optical knife-edge detector. By this method, ultrasonic images with a resolution given by the tip diameter of several tenths of nanometers were obtained. The image contrast originates mainly from the local variation of the attractive and repulsive nonlinear forces between the sensor tip and the sample surface, which are responsible for the ultrasonic transmission from the sample surface to the sensor tip. A method in how to determine the surface elastic constants from the cantilever vibration spectra is suggested.