Fabrication of ferroelectric Fe doped HfO2 epitaxial thin films by ion-beam sputtering method and their characterization

In this study, the effect of Fe doping on the crystal structure and electrical properties in 20-nm-thick HfO2 epitaxial thin films were systematically investigated. X-ray diffraction measurements revealed that undoped HfO2 films were composed of a paraelectric monoclinic phase. On the other hand, the formation of non-centrosymmetric orthorhombic phase was observed in Fe doped HfO2 films and was most promoted at an optimum doping concentration. In addition, high-temperature X-ray diffraction measurements showed that an orthorhombic phase to a highly symmetric phase transition occurs between 500 and 600 degrees C. Microstructural analysis using scanning transmission electron microscopy revealed multidomain structure consisting of orthorhombic and monoclinic phases. Ferroelectricity depended on Fe doping concentration, and the maximum remanent polarization value was 8.8 mu C/cm(2). These results indicate that Fe doped HfO2 thin films can be applied as nanoscale ferroelectrics. (C) 2018 The Japan Society of Applied Physics