Modelling of Pyroelectric Response in Inhomogeneous Ferroelectric-Semiconductor Films

TL;DR

This paper develops a modified Landau-Khalatnikov model to describe the pyroelectric response of inhomogeneous ferroelectric-semiconductor films, capturing the effects of disorder and defects on hysteresis behavior.

Contribution

It introduces a set of six coupled equations for inhomogeneous pyroelectric response, explaining the transition from sharp to smooth hysteresis loops due to defects.

Findings

Pyroelectric hysteresis loops become smoother and lower with increased disorder.

Defect concentration reduces coercive field and peak pyroelectric response.

Model shows good agreement with experimental data on Pb(Zr,Ti)O3 films.

Abstract

We have modified Landau-Khalatnikov approach and shown that the pyroelectric response of inhomogeneous ferroelectric-semiconductor films can be described by using six coupled equations for six order parameters: average displacement, its mean-square fluctuation and correlation with charge defects density fluctuations, average pyroelectric coefficient, its fluctuation and correlation with charge defects density fluctuations. Coupled equations demonstrate the inhomogeneous reversal of pyroelectric response in contrast to the equations of Landau-Khalatnikov type, which describe the homogeneous reversal with the sharp pyroelectric coefficient peak near the thermodynamic coercive field value. Within the framework of our model pyroelectric hysteresis loop becomes much smoother, thinner and lower as well as pyroelectric coefficient peaks near the coercive field completely disappear under the increase of disordering caused by defects. This effect is similar to the well-known "square to slim transition" of the ferroelectric hysteresis loops in relaxor ferroelectrics. Also the increase of defect concentration leads to the drastic decrease of the coercive field typical for disordered ferroelectrics. Usually pyroelectric hysteresis loops of doped and inhomogeneous ferroelectrics have typical smooth shape without any pyroelectric coefficient peaks and coercive field values much lower than the thermodynamic one. Therefore our approach qualitatively explains available experimental results. Rather well quantitative agreement between our modelling and typical Pb(Zr,Ti)O3-film pyroelectric and ferroelectric loops has been obtained.