First-order reversal curve diagrams for characterizing ferroelectricity of Hf0.5Zr0.5O2 films grown at different rates

Abstract

The ferroelectric properties of Hf0.5Zr0.5O2 (HZO) films deposited by atomic layer deposition using various growth rates were systematically investigated by analyzing first-order reversal curve (FORC) diagrams. The FORC diagram is a valuable methodology for characterization of ferroelectric switching by evaluation of subloop hysteresis. These diagrams are tremendously sensitive to changes in the hysteresis loops which can be used to describe switching characteristics. HZO films with a growth rate of 1.5 Å/cycle showed two oppositely biased regions in switching density plots. When decreasing the growth rate to 1.2 and 0.98 Å/cycle, these internal bias fields disappeared, showing one maximum switching current peak. Furthermore, the device fabricated with a growth rate of 1.2 Å/cycle showed the clearest switching current peak, indicating an increase in the magnitude of the switching current, as well as increased remanent polarization. In this paper, the FORC diagram and the result of pulse switching measurements suggest that the growth rate of the thin film is a crucial factor to determine the high quality of HZO ferroelectric films.