Realization of ferroelectricity in sputtered Al 1-x Sc x N films with a wide range of Sc content

The ferroelectric properties of wurtzite-structured Al 1-x Sc x N thin films are affected simultaneously by the Sc concentration and in-plane stress state, however, the interaction between these two factors remains unclear. In this work, a series of Al 1-x Sc x N films were deposited on (111) Si substrate by dual-target co-sputtering. X-ray diffraction analyses show the films with a wide range of Sc content (x= 0.05 - 0.50) have the (0002)-textured wurtzite structure and are in compressive stress state. Ferroelectricity in all the films is confirmed by polarization hysteresis loop measurements at room temperature, and the coercive field exhibits an interesting non-monotonic transition due to the competition between in-plane stress and Sc incorporation. The results provide insight into the wurtzite-structure stability and the nature of ferroelectricity for Al 1-x Sc x N thin films.