FORCE MICROSCOPY FOR THE INVESTIGATION OF HIGH-FREQUENCY SURFACE-ACOUSTIC-WAVE DEVICES

Surface acoustic wave (SAW) devices are of great importance in mobile communication and signal processing applications. For their optimizati on second-order effects, like diffraction or mass loading, have to be studied. However, meeting today's demands of GHz operation new ways of wave field mapping have to be developed, since common methods, like l aser optical or electron microscope probing, are resolution limited to the micron range. Scanning acoustic force microscopy (SAFM) allows th e detection of the high-frequency surface oscillations having sub-Angs trom amplitudes with the force microscope's typical lateral resolution . The key for measuring the high mechanical frequencies is the nonline ar force curve. Another approach is the force microscope mapping of re arranged fine particles, revealing the nodes and antinodes of the stan ding wave field. We present measurements in the near field of, and wit hin, acoustic devices fabricated on piezoelectric substrates, such as LiNbO3 and quartz, and being operated at frequencies around 600 MHz. B y employing SAFM, the local influence of the electrodes on the wave fi eld, leading to undesired performance losses, was investigated.