X-ray imaging and diffraction from surface phonons on GaAs

Surface acoustic waves (SAWs) are excited on the GaAs (001) surface by usin g interdigital transducers, designed for frequencies of up to 900 MHz. The emitted phonons with wavelengths down to 3.5 mu m are visualized and charac terized by combined x-ray diffraction techniques. Using stroboscopic topogr aphy, the SAW emission of a parallel and a focusing transducer geometry are imaged. High-resolution x-ray diffraction profiles show up to 12 phonon-in duced satellite reflections besides the GaAs (004) reflection, with a width of 9 arcsec each. The diffraction pattern is simulated numerically, applyi ng the kinematical scattering theory to a model crystal. From fits to measu red diffraction profiles at different excitation voltages, the SAW amplitud es were calculated and found to be in the sub-nm range. (C) 1999 American I nstitute of Physics. [S0003- 6951(99)01538-7].