Evaluation of piezoelectric Ta2O5 thin films deposited on SrTiO3 substrates

Abstract

Tantalum pentoxide (Ta2O5) piezoelectric thin films were deposited on (100) and (110) planes of strontium titanate (SrTiO3) substrates using an RF magnetron sputtering system. The crystallinity and Rayleigh-type surface acoustic wave propagation properties of the thin films were evaluated. The possibility that the Ta2O5 thin films were crystallized to orthorhombic Ta2O5 on SrTiO3 substrates by providing a buffer layer deposited without applying O2 radical power was demonstrated. From measured pole figures, it is considered that the crystalline Ta2O5/SrTiO3(100) sample has two lattice arrangements orthogonal to each other, and the crystalline Ta2O5/SrTiO3(110) sample has a single lattice arrangement. For a normalized film thickness h/λ of 0.45, the propagation loss for the deposition on SrTiO3(110) was 0.02 dB/λ, whereas that for the X-axis-oriented Ta2O5 thin film on SiO2 substrate was 0.21 dB/λ. Unfortunately, the coupling factor of the crystalline thin film was less than 0.3% for h/λ ranging from 0.29 to 0.45.