Fine tuning of s.a.w. resonators using argon ion bombardment

High-energy (40 to 240 keV) argon ion beams have been used for fine tuning of the stop/passband frequency (nominally 157 MHz) of Al/quartz Rayleigh wave transmission filters. An increase in frequency (accompanied by a reduction in impedance ratio) occurred for high ion energies and low ion doses, where the dominant effect appears to be amorphisation of the quartz surface with a reduction in mass loading due to swelling. The frequency shift was+120 kHz per 100 keV of bombarding ion energy for an ion dose of 1.5×1016 ions/cm2. A decrease in frequency occurred for low ion energies and high ion doses caused by the difference in sputtering rate between the quartz and the Al digits. The frequency shift in this case was ¿100 kHz for a dose of 1×1017 ions cm¿2