Strain engineering of ferroelectric negative capacitance in PbZr(1-)Ti O3 thin films

Abstract Negative capacitance (NC) in ferroelectric materials has been proposed to overcome the fundamental limitation on the energy efficiency of electronics. Understanding the impact of mechanical strain on the NC of ferroelectrics is of scientific significance and technological importance because the strain-polarization coupling could substantially influence the multifunctional properties of epitaxial ferroelectric thin films. Based on time-dependent Ginzburg-Landau equation and Kirchhoff's law, we reveal that a tensile strain decreases the magnitude and duration time of the transient NC of PbZr(1-x)TixO3 (PZT) thin films while a compressive strain increases it in a resistor-ferroelectric capacitor circuit. In particular, the tensile strain makes the transient NC completely disappear near the morphotropic phase boundary (MPB), whereas the compressive strain can maintain it up to a temperature higher than Curie temperature. The detailed energy analysis reveals that the change of transient NC with strain and composition is attributed to the change of the negative curvature of energy landscape, which is the origin of NC in ferroelectric materials. The work gives considerable new insight into the mechanical control of ferroelectric transient NC, and offers guidance in searching for large transient NC in the widely used PZT thin films through strain and composition engineering.