INTERACTION OF LASER-GENERATED SURFACE ACOUSTIC PULSES WITH FINE PARTICLES - SURFACE CLEANING AND ADHESION STUDIES

The mechanical forces associated with the surface acceleration in high -amplitude surface acoustic waves (SAWs) detach the particles from the surface. The removal of micron sized particles with a nanosecond SAW pulse excited by a focused laser beam in a silicon wafer was quantitat ively investigated. Both vertical and horizontal particle displacement s have been observed. It is shown that for nanosecond SAW pulses the l imit of the surface acceleration of about 10(10) m/s(2) is set by the fracture of the material and corresponds to the removal of particles l arger than about 0.05 mu m. In addition, the nonlinear transformation of the excited SAW pulses results in an increase of the surface accele ration and contributes to the cleaning process extending it to even sm aller particle dimensions. The technique is applicable in vacuum and i mproves the energetic effectiveness of the cleaning due to the removal of particles not only in the irradiated region, but also in the wider area covered by the SAW pulse propagation. It can be also used for th e determination of the Hamaker constant of the adhesion force. (C) 199 8 American Institute of Physics. [S0021-8979(98)02317-2].