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

Abstract

The ferroelectricity of HfO2 thin films is technologically useful with various advantages compared to conventional ferroelectrics. However, the application of orthorhombic HfO2 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 HfO2 (transition state) because of its intrinsic 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.