The interplay between imprint, wake-up, and domains in ferroelectric Al0.70Sc0.30N

Abstract

This paper investigates wake-up and imprint in ferroelectric Al0.70Sc0.30N films. The study employs a series of electrical measurements with varying field amplitudes and waveforms to understand the origin and underlying principle of wake-up and imprint as well as their relation. It is shown that the material can be considered wake-up free. However, inherent imprint and imprint variation of the polarization-electric field hysteresis in combination with minor loops result in a wake-up like effect. This effect is most likely related to the formation of persistent inversion domain nuclei—a mechanism that is discussed in detail and compared with alternative explanations based on charged defects. Investigations using unipolar fields are conducted to explore the reversibility of imprint and ways to program it, while partial switching is applied to investigate domain propagation and support the aforementioned explanation for the evolution of the polarization-electric field hysteresis. It is concluded that after an energetically more demanding domain nucleation, domain wall motion can switch the majority of polarization in Al1−xScxN. As a consequence, the presence of initial domains reduces the coercive field with respect to unipolar films.