Coercive Field Control in Epitaxial Ferroelectric Hf0.5Zr0.5O2 Thin Films by Nanostructure Engineering

The discovery of ferroelectric hafnium oxide has spurred great interest in the semiconductor industry, enabled by its complementary metal-oxide-semiconductor compatibility and scalability. However, many questions remain regarding the origin of the ferroelectric phases and the tunability of ferroelectric properties. In this work, we explore the influence of laser fluence on coercive field (<i>E</i>_c) in 10 nm-thick epitaxial rhombohedrally distorted orthorhombic (<i>r</i>-d <i>o</i>) Hf_0.5Zr_0.5O₂ (HZO) films grown by pulsed laser deposition on La_0.7Sr_0.3MnO₃-buffered (001) SrTiO₃ substrates. When laser fluence is decreased from 1.3 J cm^-2 to 0.5 J cm^-2, the E_c decreases from ∼3.3 to ∼2.7 MV/cm. Lower laser fluence produces pure (111) oriented grains, while higher laser fluence produces an additional (11-1) orientation, leading to low angle tilt grain boundaries and associated dislocations which can act as domain pinning sites. The stabilization of the (11-1) orientation and the grain tilting at higher deposition energetics are consistent with density functional theory calculations. To achieve a low <i>E</i>_c in HZO, which is important for energy-efficient ferroelectric memory applications, low energetic growth conditions are required, producing the most highly perfect films.