Advances and challenges in novel non-perovskite-based ferroelectrics film for memory device applications

Abstract Thin films of ferroelectric materials have been investigated for various applications because of their high dielectric constants, as well as piezoelectric and ferroelectric properties. Ferroelectricity has been explored for memory applications because of its two stable states after releasing an electric field, depending on the direction. Perovskite-based ferroelectrics have been studied for the last 30 years for these applications and have already been commercialized. However, the degradation of their ferroelectricity with decreasing film thickness (below 30 nm) makes high-density memory applications difficult. A recent "discovery" of novel ferroelectrics, e.g., fluorite-type structure HfO2-based films and wurtzite structure AlN-, GaN-, and ZnO-based films, have enabled significant reductions in film thickness without noticeable degradation. In this article, we discuss the status and challenges of these novel non-perovskite-based ferroelectric films mainly for memory device applications.