Development of ferroelectricity with crystallographic phase transformation in Hf0.5Zr0.5O2 thin films upon initial stimulation of an electric field exceeding the coercive field

Abstract

This study demonstrates a drastic transformation of ferroelectricity and crystallographic phase in Hf0.5Zr0.5O2 (HZO) thin films through the first stimulation of an electric field larger than the coercive field in metal-ferroelectric-metal (MFM) capacitors. Initially, capacitance–voltage (C–V) measurements in fresh MFM capacitors with voltage sweep smaller than the coercive field indicated constant capacitance value without hysteresis. Applying the electric field exceeding the coercive field subsequently, the C–V behavior changed to a typical dual-peak ferroelectric feature in positive and negative sweeps. X-ray diffraction analysis of the HZO layers before and after a single electric-field application revealed small-angle shifts in diffraction peaks, confirming a crystallographic phase transformation induced by the single electric-field stimulation exceeding the coercive field. These results suggest a possibility that the first electric field apply initiates development of ferroelectric phase transformation from a non-ferroelectric phase.