Regulating crystal structure and ferroelectricity in Sr doped HfO2 thin films fabricated by metallo-organic decomposition

Abstract HfO 2 based binary ferroelectric oxides are promising candidate for nonvolatile memory devices due to their compatibility with the current Si-based technology. In this work, Sr doped HfO 2 (Sr:HfO 2 ) ferroelectric thin films with Sr concentration from 0% to 10 mol% were prepared on the platinum electrodes by metallo-organic decomposition (MOD). It was demonstrated that uniform Sr:HfO 2 thin films with extremely low roughness can be achieved and crystallized by MOD under a 700 °C annealing process. A wake-up stage was believed more essential for the ferroelectricity of the MOD derived Sr:HfO 2 thin film, since the remnant polarization of 13.3 µC/cm 2 and high dielectric constant of 30 were obtained after 10 5 cycling tests. The transformation from monoclinic phase to cubic phase was observed with increasing the Sr concentration and the thickness of the films. X-ray photoelectron spectroscopy analysis confirmed the bonding type of O-Hf-O and O-Sr-O bonds in the film. The microscopic crystal structure of ferroelectric orthorhombic phase was observed by high resolution transmission electronic microscope. The intrinsic ferroelectricity of Sr:HfO 2 film was demonstrated by the hysteresis polarization-voltage loops and distinct current peaks in the current-voltage curve. Stable domain structure and its switching dynamics were monitored by piezoresponse force microscopy, indicating the native polarization of Sr:HfO 2 . This work will provide a controllable routine to fabricate ferroelectric HfO 2 based thin films using MOD method.