Epitaxial SM-Doped PMN-Pt Film with High Piezoelectric Constant for MEMS Application

We have investigated the composition dependence of the piezoelectric properties (|e
31,f
|) of Sm-doped Pb(Mg
1/3
,Nb
2/3
)O
3
-PbTiO
3
(Sm-PMN-PT) monocrystalline thin films as a candidate of transducer thin films with giant piezoelectric property beyond Pb(Zr,Ti)O
3
. Sm-PMN-PT thin films with various PMN/PT ratio were sputter-deposited on Si wafers covered with a buffer layer. The composition ratio was tuned by changing the PMN/PT ratio in the sputtering target. All thin films had excellent crystallinities, few pyrochlore phases, and (100)/(001) preferential orientations. The piezoelectric property of the thin film was evaluated by actuating a piezoelectric unimorph cantilever. As a result, the thin film which was prepared by the sputtering target with PMN/PT ratio of 50/50 showed |e
31,f
| as large as 24 C/m
²
. We believe that this thin film has a potential to break the performance limitation of piezo MEMS actuators.