Selective modal excitation in coupled piezoelectric microcantilevers

We study in detail the first vibration modes of a piezoelectric resonator based on two coupled micro-cantilevers, also known as tuning-forks. A multiple electrode geometry lying on a layer of piezoelectric AlN allows the selective excitation of different modes, including in-plane modes. A complete optical characterization of the devices in the z- and also the x-direction has been performed employing a Doppler vibrometer. The measurements confirm the excitation and inhibition of different modes depending on the actuation signals distribution on the electrodes. The influence of the dimensions of the resonator on the coupling between the microcantilevers has also been studied. Quality factors above 4,300 have been measured for the first anti-phase in-plane mode.