Effect of Spontaneous Polarization Screening on Dielectric Response of Ferroelectric Polydomain Films

A theoretical study on the effect of spontaneous polarization screening on the dielectric response of ferroelectric films with 180° domains going through the film thickness (through-domains) is presented. It has been shown by several researchers that the dielectric response of ferroelectrics is always deteriorated (e.g. due to electric field, mechanical stress, or lattice imperfections) in the thin electrode-adjacent passive regions. As a result, these regions behave as a low dielectric material reducing the total dielectric response of the ferroelectric capacitor. This “depolarizing” effect can be modeled by a low-dielectric layer between the ferroelectric and the electrode. The strong electric field in the dielectric layer can induce free charge injection from the electrode to the ferroelectric-dielectric layer interface. We study how these free charges affect the dielectric response of the ferroelectric capacitor with through-domains. We found that their presence strongly influences the domain wall contribution to permittivity of the ferroelectric. This effect is controlled to a great extent by the domain wall thickness.

Keywords:

• Dielectric thin films
• capacitors
• domain structure

PACS numbers:

• 77.55.+f
• 84.32.Tt
• 77.80.Dj

Acknowledgments

This project was supported by the Swiss National Science Foundation, by the Ministry of Education of the Czech Republic (MSM 242200002), and by the Grant Agency of the Czech Republic (GACR 202/03/0569).