Role of Si Doping in Reducing Coercive Fields for Ferroelectric Switching in HfO2

Abstract

The ferroelectricity of ${\mathrm{Hf}\mathrm{O}}_{2}$ thin films is technologically useful with various advantages compared to conventional ferroelectrics. However, the application of orthorhombic ${\mathrm{Hf}\mathrm{O}}_{2}$ has been limited by its large coercive field compared to perovskite-based ferroelectrics. Using first-principles calculations, we extensively search for 34 dopant elements to reduce the problematic coercive fields and discover that the coercive fields exhibit a simple volcano shape against the dopant's size. We also discover that the Si dopant is a critical element in stabilizing tetragonal phase ${\mathrm{Hf}\mathrm{O}}_{2}$ (transition state) because of its intrinsic ${\mathrm{sp}}^{3}$ bond favoring characteristics with oxygen, thereby notably lowering the coercive fields. We provide an atomic scale picture to understand the excellent role of Si in effective ferroelectric switching and a simple rule to tune coercive fields with various doping agents.