Microstructural evolution of the abnormal crystallite grains in sputtered ScAlN film for piezo-MEMS applications

Scandium aluminum nitride (ScAlN) thin film has received wide attention for high performance piezo-MEMS device development. This work studies the large-size abnormal grains in the reactive sputtered ScAlN films. Our experimental results prove the abnormal grain nucleates in the normal film matrix and grows larger along the film thickness direction. The local in-plane strain induced by the lattice deformation results in atomic stacking fault, which is suggested to drive the abnormal nucleation.