Structural characterization of the abnormal grains evolution in sputtered ScAlN films

The mis-oriented abnormal grains embedded in the sputtered scandium aluminum nitride (ScAlN) film degrade the film piezoelectric response. In this paper, we present for the first time the in-plane TEM observation of the crystal grains morphology and the microstructure of the sputtered Sc
0.2
Al
0.8
N film. The columnar normal grains are highly (0002) textured and exhibit the hexagonal cross-section morphology with six well-developed {1011} side facets. The abnormal grains show irregular cross-section. The grain boundary study reveals that the abnormal grains grow laterally and consume their neighboring normal grains during the film sputtering.