Investigation of the local polarization switching behavior in La-doped HfO2 structures

The discovery of ferroelectricity in hafnium oxide (HfO₂) based thin films is a promising step towards the realization of ferroelectric based memory devices due to their inherent advantages over conventional perovskite materials, especially their compatibility with existing CMOS technology. Although several studies have reported the integral behavior of the capacitors, an in-depth investigation of the local ferroelectric characteristics has not yet been performed. Here, we will discuss the wake-up behavior and the polarization switching dynamics in ultrathin La-doped HfO₂ capacitors investigated by means of Piezoresponse Force Microscopy (PFM). Evolution of the domain structure as a function of the applied voltage confirmed that de-pinning of domains is responsible for the increase in polarization upon field cycling. Step-by-step switching of the polarization coupled with PFM imaging revealed that the domains grow from grain boundaries or pinned domains, if present, following the nucleation limited switching (NLS) model.