Direct imaging of grain and domain structure in nanocrystalline ferroelectric thin films

Ultrathin doped HfO₂ ferroelectric films are gaining increasing interest for next-generation computing technologies such as field-effect transistors, memories, and neuromorphic devices thanks to their high performance, reliability, and CMOS compatibility. However, when grown by atomic layer deposition on silicon, these polycrystalline films contain a distribution of grain sizes and multiple structural phases, and the relationship between these structural features and the electrical response is not fully understood. We will present our work towards correlative imaging of the grain and domain structure in Zr-doped HfO₂ (HZO) films and superlattices with nm-scale resolution using advanced electron microscopy approaches, including off-axis electron holography and scanning electron nanodiffraction with in-situ electrical biasing. We will discuss links observed so far between grain structure, including size, orientation, and phase, and the electrostatic potential distribution in the film. Finally, we will discuss opportunities for further development of these approaches as well as how our initial observations can inform pathways to improve device performance and scalability.