DETERMINATION OF ULTRASONIC-ATTENUATION IN SMALL SAMPLES OF SOLID MATERIAL BY SCANNING ACOUSTIC MICROSCOPY WITH PHASE-CONTRAST

The attenuation of solid material or droplets of viscous liquids depos ited on planar substrates is measured in the frequency regime from 300 MHz to 1.2 GHz by scanning acoustic microscopy with phase contrast. T he observed spatial variations of the phases and amplitudes of the ult rasonic waves reflected from the objects contain sufficient informatio n to determine the attenuation and velocity of ultrasonic waves in aco ustically isotropic samples of minimal thickness about 1 mu m and late ral extension down to 10 mu m. The basic principles are discussed and an approximate treatment is presented together with typical results.