Deposition and evaluation of Ta 2 O 5 piezoelectric thin film on Pt crystal film

Tantalum pentoxide (Ta 2 O 5 ) thin films were deposited on Pt(100)/Si(100) and SrRuO 3 (SRO)/Pt(100)/Si(100) substrates using an RF magnetron sputtering system. From the evaluated orientation and piezoelectricity of the deposited thin films, it was clarified that the Ta 2 O 5 thin films were crystallized to λ -Ta 2 O 5 without piezoelectricity on the Pt/Si substrates and to β -Ta 2 O 5 with piezoelectricity on the SRO/Pt/Si substrates. The electromechanical coupling factor k t 2 of the deposited film containing β -Ta 2 O 5 was measured to be 0.36% from the response of a high-overtone bulk acoustic resonator, whereas that of the deposited film containing λ -Ta 2 O 5 was measured to be 0.03%. Furthermore, the enhancement of the electromechanical coupling factor of surface acoustic waves (SAWs) by adding a high-density Pt intermediate layer was clarified from the resonance property simulated by the finite element method. This enhancement was due to the distributed particle displacement of the SAWs throughout the Ta 2 O 5 thin film.