关键词: improved ferroelectricity, interfacial stress engineering, compressive strain, HfO$_{2}$

Abstract: Ferroelectric HfO$_{2}$ has attracted much attention owing to its superior ferroelectricity at an ultra-thin thickness and good compatibility with Si-based complementary metal-oxide-semiconductor (CMOS) technology. However, the crystallization of polar orthorhombic phase (o-phase) HfO$_{2}$ is less competitive, which greatly limits the ferroelectricity of the as-obtained ferroelectric HfO$_{2}$ thin films. Fortunately, the crystallization of o-phase HfO$_{2}$ can be thermodynamically modulated via interfacial stress engineering. In this paper, the growth of improved ferroelectric Al doped HfO$_{2}$ (HfO$_{2}$:Al) thin films on (111)-oriented Si substrate has been reported. Structural analysis has suggested that nonpolar monoclinic HfO$_{2}$:Al grown on (111)-oriented Si substrate suffered from a strong compressive strain, which promoted the crystallization of (111)-oriented o-phase HfO$_{2}$ in the as-grown HfO$_{2}$:Al thin films. In addition, the in-plane lattice of (111)-oriented Si substrate matches well with that of (111)-oriented o-phase HfO$_{2}$, which further thermally stabilizes the o-phase HfO$_{2}$. Accordingly, an improved ferroelectricity with a remnant polarization (2$P_{\rm r}$) of 26.7 μC/cm$^{2}$ has been obtained. The results shown in this work provide a simple way toward the preparation of improved ferroelectric HfO$_{2}$ thin films.

Key words: improved ferroelectricity, interfacial stress engineering, compressive strain, HfO$_{2}$