Planar Single-Layer Lithium Niobate Piezoelectric Transducer with no Passive Layer

This work reports a novel planar, single-layer (unimorph) piezoelectric acoustic transducer operating in its fundamental flexural mode without the use of a passive layer. The new design leverages the strong thickness shear $e_{35}$ piezoelectric coupling coefficient in X -cut lithium niobate (LN) platform, efficiently transducing between the thickness direction electrical field and a flexural vibration. The proposed platform features high figures of merit $(\text{FoM},\left.e / \sqrt{\varepsilon_T \cdot \tan (\delta)}\right)$ for acoustic receiver applications, promising for low-cost, resilient piezoelectric transducers. As a proof-of-concept, a prototype LN device was fabricated and mounted on a silicon carbide (SiC) carrier substrate. The transducer was characterized both electrically, using an impedance analyzer, and mechanically, with a laser Doppler vibrometer (LDV). The measurements confirm unimorph operation at 237 kHz with an extracted electro-mechanical coupling coefficient $(k^{2})$ of 0.9%. These results establish a new pathway for simplified acoustic transducer design using a single active piezoelectric layer.