*Article* **SAW Resonators and Filters Based on Sc0.43Al0.57N on Single Crystal and Polycrystalline Diamond**

**Miguel Sinusia Lozano 1,2 , Laura Fernández-García 3,4, David López-Romero <sup>5</sup> , Oliver A. Williams <sup>6</sup> and Gonzalo F. Iriarte 3,\***


**Abstract:** The massive data transfer rates of nowadays mobile communication technologies demand devices not only with outstanding electric performances but with example stability in a wide range of conditions. Surface acoustic wave (SAW) devices provide a high Q-factor and properties inherent to the employed materials: thermal and chemical stability or low propagation losses. SAW resonators and filters based on Sc0.43Al0.57N synthetized by reactive magnetron sputtering on single crystal and polycrystalline diamond substrates were fabricated and evaluated. Our SAW resonators showed high electromechanical coupling coefficients for Rayleigh and Sezawa modes, propagating at 1.2 GHz and 2.3 GHz, respectively. Finally, SAW filters were fabricated on Sc0.43Al0.57N/diamond heterostructures, with working frequencies above 4.7 GHz and ~200 MHz bandwidths, confirming that these devices are promising candidates in developing 5G technology.

**Keywords:** SAW devices; piezoelectricity; ScAlN thin film; diamond thin film; 5G technology; electromechanical coupling coefficient k2; Q-factor
