Operando X‐Ray Diffraction Analysis of Microscopic Structural Response in 33‐ and 31‐Mode Geometries Under an Applied Electric Field in (100)/(001)‐Oriented Epitaxial Tetragonal Pb(Zr, Ti)O 3 Films Grown on (100) Si Substrates

Piezoelectric thin films have been widely used in microelectromechanical systems (MEMS), where Pb(Zr x Ti 1‐ x )O 3 is a representative material. To achieve significant piezoelectric responses, multidomain structural changes under electric fields must be understood via domain‐lattice observations. Here, (100)/(001)‐oriented tetragonal Pb(Zr x Ti 1‐ x )O 3 epitaxial films with a small (001)‐oriented domain fraction were grown on (100) Si substrates for piezo‐MEMS. Although previous studies have primarily focused on out‐of‐plane piezoelectric responses (33‐mode actuation), in‐plane (31‐mode actuation) is predominantly utilized in piezo‐MEMS devices. Therefore, we investigate the microscopic structural responses associated with both modes. Operando synchrotron x‐ray diffraction under pulsed electric fields applied perpendicular to the film surface was used to probe out‐of‐plane and in‐plane lattice evolution. Domain switching from (100) to (001) was accompanied by in‐plane lattice elongation and out‐of‐plane shrinkage due to substrate‐clamping. Time‐resolved measurements revealed out‐of‐plane lattice dynamics between domain orientations during pulse application. This study provides an operando correlation between ferroelastic domain switching and both out‐of‐plane and in‐plane lattice responses relevant to 33‐ and 31‐mode actuation in Si‐compatible multidomain Pb(Zr x Ti 1‐ x )O 3 films, providing key insights for optimizing the piezoelectric properties of clamped epitaxial films for MEMS applications.