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(2P_(r))of 26.7C/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.
本研究专注于稀土金属Y和La掺下HfO2薄膜的铁电性。采用脉冲激光沉积技术,在(001)取向SrTiO3衬底上利用La0.7Sr0.3MnO3薄膜作为底电极,成功实现了沿(111)取向生长的外延薄膜。研究发现,掺杂下的HfO2薄膜呈现出较好的结晶性,在室温下压电系数d33约为6 pm/V,畴翻转可达180˚,剩余极化强度可达到12.91 μC/cm2,表现出良好的铁电性。这些实验成果为基于HfO2薄膜的电子器件设计提供了重要的实验基础。This study focuses on the ferroelectric properties of Y and La doped HfO2 thin films. The epitaxial films grown along the (111) orientation were successfully prepared on (001)-oriented SrTiO3 substrate using La0.7Sr0.3MnO3 film as the substrate electrode by Pulsed laser deposition technique. The results show that the doped HfO2 films exhibit good crystallinity, the piezoelectric coefficient d33 is about 6 pm/V at room temperature, the domain inversion can reach 180˚, and the residual polarization strength can reach 12.91 μC/cm2, exhibit good ferroelectric properties. These experimental results provide an important experimental basis for the design of electronic devices based on HfO2 thin films.
