Large figure-of-merit epitaxial Pb(Mn,Nb)O3-Pb(Zr,Ti)O3/Si transducer for piezoelectric MEMS sensors

A large figure-of-merit (FOM) piezoelectric transducer has been developed based on a Pb(Mn,Nb)O
₃
-Pb(Zr,Ti)O
₃
(PMnN-PZT) epitaxial thin film on a Si substrate for MEMS (Micro Electro Mechanical Systems) sensors such as vibratory gyroscopes. A c-axis oriented PMnN-PZT thin film was epitaxially grown on a Si substrate covered with buffer layers by sputter deposition with fast cooling. This film has excellent properties of a large piezoelectric coefficient (e
_31,f
, ~-14 C/m
²
), a small dielectric constant (ε
_r33
, ~200), and high Curie temperature (T
_c
, >500°C) compared to PZT-based bulk ceramics. The calculated FOM for piezoelectric MEMS gyroscopes reached 110 GPa, which is 5 times larger than those of conventional PZT polycrystalline thin films. We believe that the epitaxial PMnN-PZT/Si transducer has a great potential for high performance piezoelectric gyroscopes.